* @author John Rose, JSR 292 EG * @since 1.7 */ public class MethodHandles { private MethodHandles() { } // do not instantiate // Android-changed: We do not use MemberName / MethodHandleImpl. // // private static final MemberName.Factory IMPL_NAMES = MemberName.getFactory(); // static { MethodHandleImpl.initStatics(); } // See IMPL_LOOKUP below. //// Method handle creation from ordinary methods. /** * Returns a {@link Lookup lookup object} with * full capabilities to emulate all supported bytecode behaviors of the caller. * These capabilities include private access to the caller. * Factory methods on the lookup object can create * direct method handles * for any member that the caller has access to via bytecodes, * including protected and private fields and methods. * This lookup object is a capability which may be delegated to trusted agents. * Do not store it in place where untrusted code can access it. *
* This method is caller sensitive, which means that it may return different * values to different callers. *
* For any given caller class {@code C}, the lookup object returned by this call * has equivalent capabilities to any lookup object * supplied by the JVM to the bootstrap method of an * invokedynamic instruction * executing in the same caller class {@code C}. * @return a lookup object for the caller of this method, with private access */ // Android-changed: Remove caller sensitive. // @CallerSensitive public static Lookup lookup() { // Android-changed: Do not use Reflection.getCallerClass(). return new Lookup(VMStack.getStackClass1()); } /** * Returns a {@link Lookup lookup object} which is trusted minimally. * It can only be used to create method handles to * publicly accessible fields and methods. *
* As a matter of pure convention, the {@linkplain Lookup#lookupClass lookup class} * of this lookup object will be {@link java.lang.Object}. * *
* Discussion: * The lookup class can be changed to any other class {@code C} using an expression of the form * {@link Lookup#in publicLookup().in(C.class)}. * Since all classes have equal access to public names, * such a change would confer no new access rights. * A public lookup object is always subject to * security manager checks. * Also, it cannot access * caller sensitive methods. * @return a lookup object which is trusted minimally */ public static Lookup publicLookup() { return Lookup.PUBLIC_LOOKUP; } /** * Performs an unchecked "crack" of a * direct method handle. * The result is as if the user had obtained a lookup object capable enough * to crack the target method handle, called * {@link java.lang.invoke.MethodHandles.Lookup#revealDirect Lookup.revealDirect} * on the target to obtain its symbolic reference, and then called * {@link java.lang.invoke.MethodHandleInfo#reflectAs MethodHandleInfo.reflectAs} * to resolve the symbolic reference to a member. *
* If there is a security manager, its {@code checkPermission} method
* is called with a {@code ReflectPermission("suppressAccessChecks")} permission.
* @param
* A lookup class which needs to create method handles will call
* {@link #lookup MethodHandles.lookup} to create a factory for itself.
* When the {@code Lookup} factory object is created, the identity of the lookup class is
* determined, and securely stored in the {@code Lookup} object.
* The lookup class (or its delegates) may then use factory methods
* on the {@code Lookup} object to create method handles for access-checked members.
* This includes all methods, constructors, and fields which are allowed to the lookup class,
* even private ones.
*
*
* In cases where the given member is of variable arity (i.e., a method or constructor)
* the returned method handle will also be of {@linkplain MethodHandle#asVarargsCollector variable arity}.
* In all other cases, the returned method handle will be of fixed arity.
*
* Discussion:
* The equivalence between looked-up method handles and underlying
* class members and bytecode behaviors
* can break down in a few ways:
*
* All access checks start from a {@code Lookup} object, which
* compares its recorded lookup class against all requests to
* create method handles.
* A single {@code Lookup} object can be used to create any number
* of access-checked method handles, all checked against a single
* lookup class.
*
* A {@code Lookup} object can be shared with other trusted code,
* such as a metaobject protocol.
* A shared {@code Lookup} object delegates the capability
* to create method handles on private members of the lookup class.
* Even if privileged code uses the {@code Lookup} object,
* the access checking is confined to the privileges of the
* original lookup class.
*
* A lookup can fail, because
* the containing class is not accessible to the lookup class, or
* because the desired class member is missing, or because the
* desired class member is not accessible to the lookup class, or
* because the lookup object is not trusted enough to access the member.
* In any of these cases, a {@code ReflectiveOperationException} will be
* thrown from the attempted lookup. The exact class will be one of
* the following:
*
* In general, the conditions under which a method handle may be
* looked up for a method {@code M} are no more restrictive than the conditions
* under which the lookup class could have compiled, verified, and resolved a call to {@code M}.
* Where the JVM would raise exceptions like {@code NoSuchMethodError},
* a method handle lookup will generally raise a corresponding
* checked exception, such as {@code NoSuchMethodException}.
* And the effect of invoking the method handle resulting from the lookup
* is exactly equivalent
* to executing the compiled, verified, and resolved call to {@code M}.
* The same point is true of fields and constructors.
*
* Discussion:
* Access checks only apply to named and reflected methods,
* constructors, and fields.
* Other method handle creation methods, such as
* {@link MethodHandle#asType MethodHandle.asType},
* do not require any access checks, and are used
* independently of any {@code Lookup} object.
*
* If the desired member is {@code protected}, the usual JVM rules apply,
* including the requirement that the lookup class must be either be in the
* same package as the desired member, or must inherit that member.
* (See the Java Virtual Machine Specification, sections 4.9.2, 5.4.3.5, and 6.4.)
* In addition, if the desired member is a non-static field or method
* in a different package, the resulting method handle may only be applied
* to objects of the lookup class or one of its subclasses.
* This requirement is enforced by narrowing the type of the leading
* {@code this} parameter from {@code C}
* (which will necessarily be a superclass of the lookup class)
* to the lookup class itself.
*
* The JVM imposes a similar requirement on {@code invokespecial} instruction,
* that the receiver argument must match both the resolved method and
* the current class. Again, this requirement is enforced by narrowing the
* type of the leading parameter to the resulting method handle.
* (See the Java Virtual Machine Specification, section 4.10.1.9.)
*
* The JVM represents constructors and static initializer blocks as internal methods
* with special names ({@code "
* In some cases, access between nested classes is obtained by the Java compiler by creating
* an wrapper method to access a private method of another class
* in the same top-level declaration.
* For example, a nested class {@code C.D}
* can access private members within other related classes such as
* {@code C}, {@code C.D.E}, or {@code C.B},
* but the Java compiler may need to generate wrapper methods in
* those related classes. In such cases, a {@code Lookup} object on
* {@code C.E} would be unable to those private members.
* A workaround for this limitation is the {@link Lookup#in Lookup.in} method,
* which can transform a lookup on {@code C.E} into one on any of those other
* classes, without special elevation of privilege.
*
* The accesses permitted to a given lookup object may be limited,
* according to its set of {@link #lookupModes lookupModes},
* to a subset of members normally accessible to the lookup class.
* For example, the {@link #publicLookup publicLookup}
* method produces a lookup object which is only allowed to access
* public members in public classes.
* The caller sensitive method {@link #lookup lookup}
* produces a lookup object with full capabilities relative to
* its caller class, to emulate all supported bytecode behaviors.
* Also, the {@link Lookup#in Lookup.in} method may produce a lookup object
* with fewer access modes than the original lookup object.
*
*
*
* Discussion of private access:
* We say that a lookup has private access
* if its {@linkplain #lookupModes lookup modes}
* include the possibility of accessing {@code private} members.
* As documented in the relevant methods elsewhere,
* only lookups with private access possess the following capabilities:
*
* Each of these permissions is a consequence of the fact that a lookup object
* with private access can be securely traced back to an originating class,
* whose bytecode behaviors and Java language access permissions
* can be reliably determined and emulated by method handles.
*
*
* If a security manager is present, member lookups are subject to
* additional checks.
* From one to three calls are made to the security manager.
* Any of these calls can refuse access by throwing a
* {@link java.lang.SecurityException SecurityException}.
* Define {@code smgr} as the security manager,
* {@code lookc} as the lookup class of the current lookup object,
* {@code refc} as the containing class in which the member
* is being sought, and {@code defc} as the class in which the
* member is actually defined.
* The value {@code lookc} is defined as not present
* if the current lookup object does not have
* private access.
* The calls are made according to the following rules:
*
* If a method handle for a caller-sensitive method is requested,
* the general rules for bytecode behaviors apply,
* but they take account of the lookup class in a special way.
* The resulting method handle behaves as if it were called
* from an instruction contained in the lookup class,
* so that the caller-sensitive method detects the lookup class.
* (By contrast, the invoker of the method handle is disregarded.)
* Thus, in the case of caller-sensitive methods,
* different lookup classes may give rise to
* differently behaving method handles.
*
* In cases where the lookup object is
* {@link #publicLookup publicLookup()},
* or some other lookup object without
* private access,
* the lookup class is disregarded.
* In such cases, no caller-sensitive method handle can be created,
* access is forbidden, and the lookup fails with an
* {@code IllegalAccessException}.
*
* Discussion:
* For example, the caller-sensitive method
* {@link java.lang.Class#forName(String) Class.forName(x)}
* can return varying classes or throw varying exceptions,
* depending on the class loader of the class that calls it.
* A public lookup of {@code Class.forName} will fail, because
* there is no reasonable way to determine its bytecode behavior.
*
* If an application caches method handles for broad sharing,
* it should use {@code publicLookup()} to create them.
* If there is a lookup of {@code Class.forName}, it will fail,
* and the application must take appropriate action in that case.
* It may be that a later lookup, perhaps during the invocation of a
* bootstrap method, can incorporate the specific identity
* of the caller, making the method accessible.
*
* The function {@code MethodHandles.lookup} is caller sensitive
* so that there can be a secure foundation for lookups.
* Nearly all other methods in the JSR 292 API rely on lookup
* objects to check access requests.
*/
// Android-changed: Change link targets from MethodHandles#[public]Lookup to
// #[public]Lookup to work around complaints from javadoc.
public static final
class Lookup {
/** The class on behalf of whom the lookup is being performed. */
/* @NonNull */ private final Class lookupClass;
/** The allowed sorts of members which may be looked up (PUBLIC, etc.). */
private final int allowedModes;
/** A single-bit mask representing {@code public} access,
* which may contribute to the result of {@link #lookupModes lookupModes}.
* The value, {@code 0x01}, happens to be the same as the value of the
* {@code public} {@linkplain java.lang.reflect.Modifier#PUBLIC modifier bit}.
*/
public static final int PUBLIC = Modifier.PUBLIC;
/** A single-bit mask representing {@code private} access,
* which may contribute to the result of {@link #lookupModes lookupModes}.
* The value, {@code 0x02}, happens to be the same as the value of the
* {@code private} {@linkplain java.lang.reflect.Modifier#PRIVATE modifier bit}.
*/
public static final int PRIVATE = Modifier.PRIVATE;
/** A single-bit mask representing {@code protected} access,
* which may contribute to the result of {@link #lookupModes lookupModes}.
* The value, {@code 0x04}, happens to be the same as the value of the
* {@code protected} {@linkplain java.lang.reflect.Modifier#PROTECTED modifier bit}.
*/
public static final int PROTECTED = Modifier.PROTECTED;
/** A single-bit mask representing {@code package} access (default access),
* which may contribute to the result of {@link #lookupModes lookupModes}.
* The value is {@code 0x08}, which does not correspond meaningfully to
* any particular {@linkplain java.lang.reflect.Modifier modifier bit}.
*/
public static final int PACKAGE = Modifier.STATIC;
private static final int ALL_MODES = (PUBLIC | PRIVATE | PROTECTED | PACKAGE);
// Android-note: Android has no notion of a trusted lookup. If required, such lookups
// are performed by the runtime. As a result, we always use lookupClass, which will always
// be non-null in our implementation.
//
// private static final int TRUSTED = -1;
private static int fixmods(int mods) {
mods &= (ALL_MODES - PACKAGE);
return (mods != 0) ? mods : PACKAGE;
}
/** Tells which class is performing the lookup. It is this class against
* which checks are performed for visibility and access permissions.
*
* The class implies a maximum level of access permission,
* but the permissions may be additionally limited by the bitmask
* {@link #lookupModes lookupModes}, which controls whether non-public members
* can be accessed.
* @return the lookup class, on behalf of which this lookup object finds members
*/
public Class lookupClass() {
return lookupClass;
}
/** Tells which access-protection classes of members this lookup object can produce.
* The result is a bit-mask of the bits
* {@linkplain #PUBLIC PUBLIC (0x01)},
* {@linkplain #PRIVATE PRIVATE (0x02)},
* {@linkplain #PROTECTED PROTECTED (0x04)},
* and {@linkplain #PACKAGE PACKAGE (0x08)}.
*
* A freshly-created lookup object
* on the {@linkplain java.lang.invoke.MethodHandles#lookup() caller's class}
* has all possible bits set, since the caller class can access all its own members.
* A lookup object on a new lookup class
* {@linkplain java.lang.invoke.MethodHandles.Lookup#in created from a previous lookup object}
* may have some mode bits set to zero.
* The purpose of this is to restrict access via the new lookup object,
* so that it can access only names which can be reached by the original
* lookup object, and also by the new lookup class.
* @return the lookup modes, which limit the kinds of access performed by this lookup object
*/
public int lookupModes() {
return allowedModes & ALL_MODES;
}
/** Embody the current class (the lookupClass) as a lookup class
* for method handle creation.
* Must be called by from a method in this package,
* which in turn is called by a method not in this package.
*/
Lookup(Class lookupClass) {
this(lookupClass, ALL_MODES);
// make sure we haven't accidentally picked up a privileged class:
checkUnprivilegedlookupClass(lookupClass, ALL_MODES);
}
private Lookup(Class lookupClass, int allowedModes) {
this.lookupClass = lookupClass;
this.allowedModes = allowedModes;
}
/**
* Creates a lookup on the specified new lookup class.
* The resulting object will report the specified
* class as its own {@link #lookupClass lookupClass}.
*
* However, the resulting {@code Lookup} object is guaranteed
* to have no more access capabilities than the original.
* In particular, access capabilities can be lost as follows:
* (It may seem strange that protected access should be
* stronger than private access. Viewed independently from
* package access, protected access is the first to be lost,
* because it requires a direct subclass relationship between
* caller and callee.)
* @see #in
*/
@Override
public String toString() {
String cname = lookupClass.getName();
switch (allowedModes) {
case 0: // no privileges
return cname + "/noaccess";
case PUBLIC:
return cname + "/public";
case PUBLIC|PACKAGE:
return cname + "/package";
case ALL_MODES & ~PROTECTED:
return cname + "/private";
case ALL_MODES:
return cname;
// Android-changed: No support for TRUSTED callers.
// case TRUSTED:
// return "/trusted"; // internal only; not exported
default: // Should not happen, but it's a bitfield...
cname = cname + "/" + Integer.toHexString(allowedModes);
assert(false) : cname;
return cname;
}
}
/**
* Produces a method handle for a static method.
* The type of the method handle will be that of the method.
* (Since static methods do not take receivers, there is no
* additional receiver argument inserted into the method handle type,
* as there would be with {@link #findVirtual findVirtual} or {@link #findSpecial findSpecial}.)
* The method and all its argument types must be accessible to the lookup object.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set.
*
* If the returned method handle is invoked, the method's class will
* be initialized, if it has not already been initialized.
* Example:
*
* When called, the handle will treat the first argument as a receiver
* and dispatch on the receiver's type to determine which method
* implementation to enter.
* (The dispatching action is identical with that performed by an
* {@code invokevirtual} or {@code invokeinterface} instruction.)
*
* The first argument will be of type {@code refc} if the lookup
* class has full privileges to access the member. Otherwise
* the member must be {@code protected} and the first argument
* will be restricted in type to the lookup class.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set.
*
* Because of the general equivalence between {@code invokevirtual}
* instructions and method handles produced by {@code findVirtual},
* if the class is {@code MethodHandle} and the name string is
* {@code invokeExact} or {@code invoke}, the resulting
* method handle is equivalent to one produced by
* {@link java.lang.invoke.MethodHandles#exactInvoker MethodHandles.exactInvoker} or
* {@link java.lang.invoke.MethodHandles#invoker MethodHandles.invoker}
* with the same {@code type} argument.
*
* Example:
*
* The requested type must have a return type of {@code void}.
* (This is consistent with the JVM's treatment of constructor type descriptors.)
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the constructor's variable arity modifier bit ({@code 0x0080}) is set.
*
* If the returned method handle is invoked, the constructor's class will
* be initialized, if it has not already been initialized.
* Example:
*
* Before method resolution,
* if the explicitly specified caller class is not identical with the
* lookup class, or if this lookup object does not have
* private access
* privileges, the access fails.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set.
*
* (Note: JVM internal methods named {@code " Example:
*
* If the returned method handle is invoked, the field's class will
* be initialized, if it has not already been initialized.
* @param refc the class or interface from which the method is accessed
* @param name the field's name
* @param type the field's type
* @return a method handle which can load values from the field
* @throws NoSuchFieldException if the field does not exist
* @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findStaticGetter(Class refc, String name, Class type) throws NoSuchFieldException, IllegalAccessException {
return findAccessor(refc, name, type, MethodHandle.SGET);
}
/**
* Produces a method handle giving write access to a static field.
* The type of the method handle will have a void return type.
* The method handle will take a single
* argument, of the field's value type, the value to be stored.
* Access checking is performed immediately on behalf of the lookup class.
*
* If the returned method handle is invoked, the field's class will
* be initialized, if it has not already been initialized.
* @param refc the class or interface from which the method is accessed
* @param name the field's name
* @param type the field's type
* @return a method handle which can store values into the field
* @throws NoSuchFieldException if the field does not exist
* @throws IllegalAccessException if access checking fails, or if the field is not {@code static}
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findStaticSetter(Class refc, String name, Class type) throws NoSuchFieldException, IllegalAccessException {
return findAccessor(refc, name, type, MethodHandle.SPUT);
}
/**
* Produces an early-bound method handle for a non-static method.
* The receiver must have a supertype {@code defc} in which a method
* of the given name and type is accessible to the lookup class.
* The method and all its argument types must be accessible to the lookup object.
* The type of the method handle will be that of the method,
* without any insertion of an additional receiver parameter.
* The given receiver will be bound into the method handle,
* so that every call to the method handle will invoke the
* requested method on the given receiver.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set
* and the trailing array argument is not the only argument.
* (If the trailing array argument is the only argument,
* the given receiver value will be bound to it.)
*
* This is equivalent to the following code:
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set.
*
* If m is static, and
* if the returned method handle is invoked, the method's class will
* be initialized, if it has not already been initialized.
* @param m the reflected method
* @return a method handle which can invoke the reflected method
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @throws NullPointerException if the argument is null
*/
public MethodHandle unreflect(Method m) throws IllegalAccessException {
if (m == null) {
throw new NullPointerException("m == null");
}
MethodType methodType = MethodType.methodType(m.getReturnType(),
m.getParameterTypes());
// We should only perform access checks if setAccessible hasn't been called yet.
if (!m.isAccessible()) {
checkAccess(m.getDeclaringClass(), m.getDeclaringClass(), m.getModifiers(),
m.getName());
}
if (Modifier.isStatic(m.getModifiers())) {
return createMethodHandle(m, MethodHandle.INVOKE_STATIC, methodType);
} else {
methodType = methodType.insertParameterTypes(0, m.getDeclaringClass());
return createMethodHandle(m, MethodHandle.INVOKE_VIRTUAL, methodType);
}
}
/**
* Produces a method handle for a reflected method.
* It will bypass checks for overriding methods on the receiver,
* as if called from an {@code invokespecial}
* instruction from within the explicitly specified {@code specialCaller}.
* The type of the method handle will be that of the method,
* with a suitably restricted receiver type prepended.
* (The receiver type will be {@code specialCaller} or a subtype.)
* If the method's {@code accessible} flag is not set,
* access checking is performed immediately on behalf of the lookup class,
* as if {@code invokespecial} instruction were being linked.
*
* Before method resolution,
* if the explicitly specified caller class is not identical with the
* lookup class, or if this lookup object does not have
* private access
* privileges, the access fails.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the method's variable arity modifier bit ({@code 0x0080}) is set.
* @param m the reflected method
* @param specialCaller the class nominally calling the method
* @return a method handle which can invoke the reflected method
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @throws NullPointerException if any argument is null
*/
public MethodHandle unreflectSpecial(Method m, Class specialCaller) throws IllegalAccessException {
if (m == null) {
throw new NullPointerException("m == null");
}
if (specialCaller == null) {
throw new NullPointerException("specialCaller == null");
}
if (!m.isAccessible()) {
checkSpecialCaller(specialCaller);
}
final MethodType methodType = MethodType.methodType(m.getReturnType(),
m.getParameterTypes());
return findSpecial(m, methodType, m.getDeclaringClass() /* refc */, specialCaller);
}
/**
* Produces a method handle for a reflected constructor.
* The type of the method handle will be that of the constructor,
* with the return type changed to the declaring class.
* The method handle will perform a {@code newInstance} operation,
* creating a new instance of the constructor's class on the
* arguments passed to the method handle.
*
* If the constructor's {@code accessible} flag is not set,
* access checking is performed immediately on behalf of the lookup class.
*
* The returned method handle will have
* {@linkplain MethodHandle#asVarargsCollector variable arity} if and only if
* the constructor's variable arity modifier bit ({@code 0x0080}) is set.
*
* If the returned method handle is invoked, the constructor's class will
* be initialized, if it has not already been initialized.
* @param c the reflected constructor
* @return a method handle which can invoke the reflected constructor
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @throws NullPointerException if the argument is null
*/
public MethodHandle unreflectConstructor(Constructor c) throws IllegalAccessException {
if (c == null) {
throw new NullPointerException("c == null");
}
if (!c.isAccessible()) {
checkAccess(c.getDeclaringClass(), c.getDeclaringClass(), c.getModifiers(),
c.getName());
}
return createMethodHandleForConstructor(c);
}
/**
* Produces a method handle giving read access to a reflected field.
* The type of the method handle will have a return type of the field's
* value type.
* If the field is static, the method handle will take no arguments.
* Otherwise, its single argument will be the instance containing
* the field.
* If the field's {@code accessible} flag is not set,
* access checking is performed immediately on behalf of the lookup class.
*
* If the field is static, and
* if the returned method handle is invoked, the field's class will
* be initialized, if it has not already been initialized.
* @param f the reflected field
* @return a method handle which can load values from the reflected field
* @throws IllegalAccessException if access checking fails
* @throws NullPointerException if the argument is null
*/
public MethodHandle unreflectGetter(Field f) throws IllegalAccessException {
return findAccessor(f, f.getDeclaringClass(), f.getType(),
Modifier.isStatic(f.getModifiers()) ? MethodHandle.SGET : MethodHandle.IGET,
f.isAccessible() /* performAccessChecks */);
}
/**
* Produces a method handle giving write access to a reflected field.
* The type of the method handle will have a void return type.
* If the field is static, the method handle will take a single
* argument, of the field's value type, the value to be stored.
* Otherwise, the two arguments will be the instance containing
* the field, and the value to be stored.
* If the field's {@code accessible} flag is not set,
* access checking is performed immediately on behalf of the lookup class.
*
* If the field is static, and
* if the returned method handle is invoked, the field's class will
* be initialized, if it has not already been initialized.
* @param f the reflected field
* @return a method handle which can store values into the reflected field
* @throws IllegalAccessException if access checking fails
* @throws NullPointerException if the argument is null
*/
public MethodHandle unreflectSetter(Field f) throws IllegalAccessException {
return findAccessor(f, f.getDeclaringClass(), f.getType(),
Modifier.isStatic(f.getModifiers()) ? MethodHandle.SPUT : MethodHandle.IPUT,
f.isAccessible() /* performAccessChecks */);
}
/**
* Cracks a direct method handle
* created by this lookup object or a similar one.
* Security and access checks are performed to ensure that this lookup object
* is capable of reproducing the target method handle.
* This means that the cracking may fail if target is a direct method handle
* but was created by an unrelated lookup object.
* This can happen if the method handle is caller sensitive
* and was created by a lookup object for a different class.
* @param target a direct method handle to crack into symbolic reference components
* @return a symbolic reference which can be used to reconstruct this method handle from this lookup object
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws IllegalArgumentException if the target is not a direct method handle or if access checking fails
* @exception NullPointerException if the target is {@code null}
* @see MethodHandleInfo
* @since 1.8
*/
public MethodHandleInfo revealDirect(MethodHandle target) {
MethodHandleImpl directTarget = getMethodHandleImpl(target);
MethodHandleInfo info = directTarget.reveal();
try {
checkAccess(lookupClass(), info.getDeclaringClass(), info.getModifiers(),
info.getName());
} catch (IllegalAccessException exception) {
throw new IllegalArgumentException("Unable to access memeber.", exception);
}
return info;
}
private boolean hasPrivateAccess() {
return (allowedModes & PRIVATE) != 0;
}
/** Check public/protected/private bits on the symbolic reference class and its member. */
void checkAccess(Class refc, Class defc, int mods, String methName)
throws IllegalAccessException {
int allowedModes = this.allowedModes;
if (Modifier.isProtected(mods) &&
defc == Object.class &&
"clone".equals(methName) &&
refc.isArray()) {
// The JVM does this hack also.
// (See ClassVerifier::verify_invoke_instructions
// and LinkResolver::check_method_accessability.)
// Because the JVM does not allow separate methods on array types,
// there is no separate method for int[].clone.
// All arrays simply inherit Object.clone.
// But for access checking logic, we make Object.clone
// (normally protected) appear to be public.
// Later on, when the DirectMethodHandle is created,
// its leading argument will be restricted to the
// requested array type.
// N.B. The return type is not adjusted, because
// that is *not* the bytecode behavior.
mods ^= Modifier.PROTECTED | Modifier.PUBLIC;
}
if (Modifier.isProtected(mods) && Modifier.isConstructor(mods)) {
// cannot "new" a protected ctor in a different package
mods ^= Modifier.PROTECTED;
}
if (Modifier.isPublic(mods) && Modifier.isPublic(refc.getModifiers()) && allowedModes != 0)
return; // common case
int requestedModes = fixmods(mods); // adjust 0 => PACKAGE
if ((requestedModes & allowedModes) != 0) {
if (VerifyAccess.isMemberAccessible(refc, defc, mods, lookupClass(), allowedModes))
return;
} else {
// Protected members can also be checked as if they were package-private.
if ((requestedModes & PROTECTED) != 0 && (allowedModes & PACKAGE) != 0
&& VerifyAccess.isSamePackage(defc, lookupClass()))
return;
}
throwMakeAccessException(accessFailedMessage(refc, defc, mods), this);
}
String accessFailedMessage(Class refc, Class defc, int mods) {
// check the class first:
boolean classOK = (Modifier.isPublic(defc.getModifiers()) &&
(defc == refc ||
Modifier.isPublic(refc.getModifiers())));
if (!classOK && (allowedModes & PACKAGE) != 0) {
classOK = (VerifyAccess.isClassAccessible(defc, lookupClass(), ALL_MODES) &&
(defc == refc ||
VerifyAccess.isClassAccessible(refc, lookupClass(), ALL_MODES)));
}
if (!classOK)
return "class is not public";
if (Modifier.isPublic(mods))
return "access to public member failed"; // (how?)
if (Modifier.isPrivate(mods))
return "member is private";
if (Modifier.isProtected(mods))
return "member is protected";
return "member is private to package";
}
// Android-changed: checkSpecialCaller assumes that ALLOW_NESTMATE_ACCESS = false,
// as in upstream OpenJDK.
//
// private static final boolean ALLOW_NESTMATE_ACCESS = false;
private void checkSpecialCaller(Class specialCaller) throws IllegalAccessException {
// Android-changed: No support for TRUSTED lookups. Also construct the
// IllegalAccessException by hand because the upstream code implicitly assumes
// that the lookupClass == specialCaller.
//
// if (allowedModes == TRUSTED) return;
if (!hasPrivateAccess() || (specialCaller != lookupClass())) {
throw new IllegalAccessException("no private access for invokespecial : "
+ specialCaller + ", from" + this);
}
}
private void throwMakeAccessException(String message, Object from) throws
IllegalAccessException{
message = message + ": "+ toString();
if (from != null) message += ", from " + from;
throw new IllegalAccessException(message);
}
private void checkReturnType(Method method, MethodType methodType)
throws NoSuchMethodException {
if (method.getReturnType() != methodType.rtype()) {
throw new NoSuchMethodException(method.getName() + methodType);
}
}
}
/**
* "Cracks" {@code target} to reveal the underlying {@code MethodHandleImpl}.
*/
private static MethodHandleImpl getMethodHandleImpl(MethodHandle target) {
// Special case : We implement handles to constructors as transformers,
// so we must extract the underlying handle from the transformer.
if (target instanceof Transformers.Construct) {
target = ((Transformers.Construct) target).getConstructorHandle();
}
// Special case: Var-args methods are also implemented as Transformers,
// so we should get the underlying handle in that case as well.
if (target instanceof Transformers.VarargsCollector) {
target = target.asFixedArity();
}
if (target instanceof MethodHandleImpl) {
return (MethodHandleImpl) target;
}
throw new IllegalArgumentException(target + " is not a direct handle");
}
/**
* Produces a method handle giving read access to elements of an array.
* The type of the method handle will have a return type of the array's
* element type. Its first argument will be the array type,
* and the second will be {@code int}.
* @param arrayClass an array type
* @return a method handle which can load values from the given array type
* @throws NullPointerException if the argument is null
* @throws IllegalArgumentException if arrayClass is not an array type
*/
public static
MethodHandle arrayElementGetter(Class arrayClass) throws IllegalArgumentException {
final Class componentType = arrayClass.getComponentType();
if (componentType == null) {
throw new IllegalArgumentException("Not an array type: " + arrayClass);
}
if (componentType.isPrimitive()) {
try {
return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class,
"arrayElementGetter",
MethodType.methodType(componentType, arrayClass, int.class));
} catch (NoSuchMethodException | IllegalAccessException exception) {
throw new AssertionError(exception);
}
}
return new Transformers.ReferenceArrayElementGetter(arrayClass);
}
/** @hide */ public static byte arrayElementGetter(byte[] array, int i) { return array[i]; }
/** @hide */ public static boolean arrayElementGetter(boolean[] array, int i) { return array[i]; }
/** @hide */ public static char arrayElementGetter(char[] array, int i) { return array[i]; }
/** @hide */ public static short arrayElementGetter(short[] array, int i) { return array[i]; }
/** @hide */ public static int arrayElementGetter(int[] array, int i) { return array[i]; }
/** @hide */ public static long arrayElementGetter(long[] array, int i) { return array[i]; }
/** @hide */ public static float arrayElementGetter(float[] array, int i) { return array[i]; }
/** @hide */ public static double arrayElementGetter(double[] array, int i) { return array[i]; }
/**
* Produces a method handle giving write access to elements of an array.
* The type of the method handle will have a void return type.
* Its last argument will be the array's element type.
* The first and second arguments will be the array type and int.
* @param arrayClass the class of an array
* @return a method handle which can store values into the array type
* @throws NullPointerException if the argument is null
* @throws IllegalArgumentException if arrayClass is not an array type
*/
public static
MethodHandle arrayElementSetter(Class arrayClass) throws IllegalArgumentException {
final Class componentType = arrayClass.getComponentType();
if (componentType == null) {
throw new IllegalArgumentException("Not an array type: " + arrayClass);
}
if (componentType.isPrimitive()) {
try {
return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class,
"arrayElementSetter",
MethodType.methodType(void.class, arrayClass, int.class, componentType));
} catch (NoSuchMethodException | IllegalAccessException exception) {
throw new AssertionError(exception);
}
}
return new Transformers.ReferenceArrayElementSetter(arrayClass);
}
/** @hide */
public static void arrayElementSetter(byte[] array, int i, byte val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(boolean[] array, int i, boolean val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(char[] array, int i, char val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(short[] array, int i, short val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(int[] array, int i, int val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(long[] array, int i, long val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(float[] array, int i, float val) { array[i] = val; }
/** @hide */
public static void arrayElementSetter(double[] array, int i, double val) { array[i] = val; }
/// method handle invocation (reflective style)
/**
* Produces a method handle which will invoke any method handle of the
* given {@code type}, with a given number of trailing arguments replaced by
* a single trailing {@code Object[]} array.
* The resulting invoker will be a method handle with the following
* arguments:
*
* The invoker will invoke its target like a call to {@link MethodHandle#invoke invoke} with
* the indicated {@code type}.
* That is, if the target is exactly of the given {@code type}, it will behave
* like {@code invokeExact}; otherwise it behave as if {@link MethodHandle#asType asType}
* is used to convert the target to the required {@code type}.
*
* The type of the returned invoker will not be the given {@code type}, but rather
* will have all parameters except the first {@code leadingArgCount}
* replaced by a single array of type {@code Object[]}, which will be
* the final parameter.
*
* Before invoking its target, the invoker will spread the final array, apply
* reference casts as necessary, and unbox and widen primitive arguments.
* If, when the invoker is called, the supplied array argument does
* not have the correct number of elements, the invoker will throw
* an {@link IllegalArgumentException} instead of invoking the target.
*
* This method is equivalent to the following code (though it may be more efficient):
*
* This method is equivalent to the following code (though it may be more efficient):
* {@code publicLookup().findVirtual(MethodHandle.class, "invokeExact", type)}
*
*
* Discussion:
* Invoker method handles can be useful when working with variable method handles
* of unknown types.
* For example, to emulate an {@code invokeExact} call to a variable method
* handle {@code M}, extract its type {@code T},
* look up the invoker method {@code X} for {@code T},
* and call the invoker method, as {@code X.invoke(T, A...)}.
* (It would not work to call {@code X.invokeExact}, since the type {@code T}
* is unknown.)
* If spreading, collecting, or other argument transformations are required,
* they can be applied once to the invoker {@code X} and reused on many {@code M}
* method handle values, as long as they are compatible with the type of {@code X}.
*
* (Note: The invoker method is not available via the Core Reflection API.
* An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
* on the declared {@code invokeExact} or {@code invoke} method will raise an
* {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)
*
* This method throws no reflective or security exceptions.
* @param type the desired target type
* @return a method handle suitable for invoking any method handle of the given type
* @throws IllegalArgumentException if the resulting method handle's type would have
* too many parameters
*/
static public
MethodHandle exactInvoker(MethodType type) {
return new Transformers.Invoker(type, true /* isExactInvoker */);
}
/**
* Produces a special invoker method handle which can be used to
* invoke any method handle compatible with the given type, as if by {@link MethodHandle#invoke invoke}.
* The resulting invoker will have a type which is
* exactly equal to the desired type, except that it will accept
* an additional leading argument of type {@code MethodHandle}.
*
* Before invoking its target, if the target differs from the expected type,
* the invoker will apply reference casts as
* necessary and box, unbox, or widen primitive values, as if by {@link MethodHandle#asType asType}.
* Similarly, the return value will be converted as necessary.
* If the target is a {@linkplain MethodHandle#asVarargsCollector variable arity method handle},
* the required arity conversion will be made, again as if by {@link MethodHandle#asType asType}.
*
* This method is equivalent to the following code (though it may be more efficient):
* {@code publicLookup().findVirtual(MethodHandle.class, "invoke", type)}
*
* Discussion:
* A {@linkplain MethodType#genericMethodType general method type} is one which
* mentions only {@code Object} arguments and return values.
* An invoker for such a type is capable of calling any method handle
* of the same arity as the general type.
*
* (Note: The invoker method is not available via the Core Reflection API.
* An attempt to call {@linkplain java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
* on the declared {@code invokeExact} or {@code invoke} method will raise an
* {@link java.lang.UnsupportedOperationException UnsupportedOperationException}.)
*
* This method throws no reflective or security exceptions.
* @param type the desired target type
* @return a method handle suitable for invoking any method handle convertible to the given type
* @throws IllegalArgumentException if the resulting method handle's type would have
* too many parameters
*/
static public
MethodHandle invoker(MethodType type) {
return new Transformers.Invoker(type, false /* isExactInvoker */);
}
// Android-changed: Basic invokers are not supported.
//
// static /*non-public*/
// MethodHandle basicInvoker(MethodType type) {
// return type.invokers().basicInvoker();
// }
/// method handle modification (creation from other method handles)
/**
* Produces a method handle which adapts the type of the
* given method handle to a new type by pairwise argument and return type conversion.
* The original type and new type must have the same number of arguments.
* The resulting method handle is guaranteed to report a type
* which is equal to the desired new type.
*
* If the original type and new type are equal, returns target.
*
* The same conversions are allowed as for {@link MethodHandle#asType MethodHandle.asType},
* and some additional conversions are also applied if those conversions fail.
* Given types T0, T1, one of the following conversions is applied
* if possible, before or instead of any conversions done by {@code asType}:
*
* The given array controls the reordering.
* Call {@code #I} the number of incoming parameters (the value
* {@code newType.parameterCount()}, and call {@code #O} the number
* of outgoing parameters (the value {@code target.type().parameterCount()}).
* Then the length of the reordering array must be {@code #O},
* and each element must be a non-negative number less than {@code #I}.
* For every {@code N} less than {@code #O}, the {@code N}-th
* outgoing argument will be taken from the {@code I}-th incoming
* argument, where {@code I} is {@code reorder[N]}.
*
* No argument or return value conversions are applied.
* The type of each incoming argument, as determined by {@code newType},
* must be identical to the type of the corresponding outgoing parameter
* or parameters in the target method handle.
* The return type of {@code newType} must be identical to the return
* type of the original target.
*
* The reordering array need not specify an actual permutation.
* An incoming argument will be duplicated if its index appears
* more than once in the array, and an incoming argument will be dropped
* if its index does not appear in the array.
* As in the case of {@link #dropArguments(MethodHandle,int,List) dropArguments},
* incoming arguments which are not mentioned in the reordering array
* are may be any type, as determined only by {@code newType}.
*
* Before the method handle is returned, the passed-in value is converted to the requested type.
* If the requested type is primitive, widening primitive conversions are attempted,
* else reference conversions are attempted.
* The returned method handle is equivalent to {@code identity(type).bindTo(value)}.
* @param type the return type of the desired method handle
* @param value the value to return
* @return a method handle of the given return type and no arguments, which always returns the given value
* @throws NullPointerException if the {@code type} argument is null
* @throws ClassCastException if the value cannot be converted to the required return type
* @throws IllegalArgumentException if the given type is {@code void.class}
*/
public static
MethodHandle constant(Class type, Object value) {
if (type.isPrimitive()) {
if (type == void.class)
throw newIllegalArgumentException("void type");
Wrapper w = Wrapper.forPrimitiveType(type);
value = w.convert(value, type);
}
return new Transformers.Constant(type, value);
}
/**
* Produces a method handle which returns its sole argument when invoked.
* @param type the type of the sole parameter and return value of the desired method handle
* @return a unary method handle which accepts and returns the given type
* @throws NullPointerException if the argument is null
* @throws IllegalArgumentException if the given type is {@code void.class}
*/
public static
MethodHandle identity(Class type) {
if (type == null) {
throw new NullPointerException("type == null");
}
if (type.isPrimitive()) {
try {
return Lookup.PUBLIC_LOOKUP.findStatic(MethodHandles.class, "identity",
MethodType.methodType(type, type));
} catch (NoSuchMethodException | IllegalAccessException e) {
throw new AssertionError(e);
}
}
return new Transformers.ReferenceIdentity(type);
}
/** @hide */ public static byte identity(byte val) { return val; }
/** @hide */ public static boolean identity(boolean val) { return val; }
/** @hide */ public static char identity(char val) { return val; }
/** @hide */ public static short identity(short val) { return val; }
/** @hide */ public static int identity(int val) { return val; }
/** @hide */ public static long identity(long val) { return val; }
/** @hide */ public static float identity(float val) { return val; }
/** @hide */ public static double identity(double val) { return val; }
/**
* Provides a target method handle with one or more bound arguments
* in advance of the method handle's invocation.
* The formal parameters to the target corresponding to the bound
* arguments are called bound parameters.
* Returns a new method handle which saves away the bound arguments.
* When it is invoked, it receives arguments for any non-bound parameters,
* binds the saved arguments to their corresponding parameters,
* and calls the original target.
*
* The type of the new method handle will drop the types for the bound
* parameters from the original target type, since the new method handle
* will no longer require those arguments to be supplied by its callers.
*
* Each given argument object must match the corresponding bound parameter type.
* If a bound parameter type is a primitive, the argument object
* must be a wrapper, and will be unboxed to produce the primitive value.
*
* The {@code pos} argument selects which parameters are to be bound.
* It may range between zero and N-L (inclusively),
* where N is the arity of the target method handle
* and L is the length of the values array.
* @param target the method handle to invoke after the argument is inserted
* @param pos where to insert the argument (zero for the first)
* @param values the series of arguments to insert
* @return a method handle which inserts an additional argument,
* before calling the original method handle
* @throws NullPointerException if the target or the {@code values} array is null
* @see MethodHandle#bindTo
*/
public static
MethodHandle insertArguments(MethodHandle target, int pos, Object... values) {
int insCount = values.length;
Class[] ptypes = insertArgumentsChecks(target, insCount, pos);
if (insCount == 0) {
return target;
}
// Throw ClassCastExceptions early if we can't cast any of the provided values
// to the required type.
for (int i = 0; i < insCount; i++) {
final Class ptype = ptypes[pos + i];
if (!ptype.isPrimitive()) {
ptypes[pos + i].cast(values[i]);
} else {
// Will throw a ClassCastException if something terrible happens.
values[i] = Wrapper.forPrimitiveType(ptype).convert(values[i], ptype);
}
}
return new Transformers.InsertArguments(target, pos, values);
}
// Android-changed: insertArgumentPrimitive is unused.
//
// private static BoundMethodHandle insertArgumentPrimitive(BoundMethodHandle result, int pos,
// Class ptype, Object value) {
// Wrapper w = Wrapper.forPrimitiveType(ptype);
// // perform unboxing and/or primitive conversion
// value = w.convert(value, ptype);
// switch (w) {
// case INT: return result.bindArgumentI(pos, (int)value);
// case LONG: return result.bindArgumentJ(pos, (long)value);
// case FLOAT: return result.bindArgumentF(pos, (float)value);
// case DOUBLE: return result.bindArgumentD(pos, (double)value);
// default: return result.bindArgumentI(pos, ValueConversions.widenSubword(value));
// }
// }
private static Class[] insertArgumentsChecks(MethodHandle target, int insCount, int pos) throws RuntimeException {
MethodType oldType = target.type();
int outargs = oldType.parameterCount();
int inargs = outargs - insCount;
if (inargs < 0)
throw newIllegalArgumentException("too many values to insert");
if (pos < 0 || pos > inargs)
throw newIllegalArgumentException("no argument type to append");
return oldType.ptypes();
}
/**
* Produces a method handle which will discard some dummy arguments
* before calling some other specified target method handle.
* The type of the new method handle will be the same as the target's type,
* except it will also include the dummy argument types,
* at some given position.
*
* The {@code pos} argument may range between zero and N,
* where N is the arity of the target.
* If {@code pos} is zero, the dummy arguments will precede
* the target's real arguments; if {@code pos} is N
* they will come after.
*
* Example:
*
* This method is also equivalent to the following code:
*
* The {@code pos} argument may range between zero and N,
* where N is the arity of the target.
* If {@code pos} is zero, the dummy arguments will precede
* the target's real arguments; if {@code pos} is N
* they will come after.
*
* Example:
*
* This method is also equivalent to the following code:
*
* The pre-processing is performed by one or more method handles,
* specified in the elements of the {@code filters} array.
* The first element of the filter array corresponds to the {@code pos}
* argument of the target, and so on in sequence.
*
* Null arguments in the array are treated as identity functions,
* and the corresponding arguments left unchanged.
* (If there are no non-null elements in the array, the original target is returned.)
* Each filter is applied to the corresponding argument of the adapter.
*
* If a filter {@code F} applies to the {@code N}th argument of
* the target, then {@code F} must be a method handle which
* takes exactly one argument. The type of {@code F}'s sole argument
* replaces the corresponding argument type of the target
* in the resulting adapted method handle.
* The return type of {@code F} must be identical to the corresponding
* parameter type of the target.
*
* It is an error if there are elements of {@code filters}
* (null or not)
* which do not correspond to argument positions in the target.
* Example:
* Here is pseudocode for the resulting adapter:
*
* If the filter returns a value, the target must accept that value as
* its argument in position {@code pos}, preceded and/or followed by
* any arguments not passed to the filter.
* If the filter returns void, the target must accept all arguments
* not passed to the filter.
* No arguments are reordered, and a result returned from the filter
* replaces (in order) the whole subsequence of arguments originally
* passed to the adapter.
*
* The argument types (if any) of the filter
* replace zero or one argument types of the target, at position {@code pos},
* in the resulting adapted method handle.
* The return type of the filter (if any) must be identical to the
* argument type of the target at position {@code pos}, and that target argument
* is supplied by the return value of the filter.
*
* In all cases, {@code pos} must be greater than or equal to zero, and
* {@code pos} must also be less than or equal to the target's arity.
* Example:
* Here is pseudocode for the resulting adapter:
*
* A collection adapter {@code collectArguments(mh, 0, coll)} is equivalent to
* one which first "folds" the affected arguments, and then drops them, in separate
* steps as follows:
*
* If the target returns a value, the filter must accept that value as
* its only argument.
* If the target returns void, the filter must accept no arguments.
*
* The return type of the filter
* replaces the return type of the target
* in the resulting adapted method handle.
* The argument type of the filter (if any) must be identical to the
* return type of the target.
* Example:
* Here is pseudocode for the resulting adapter:
*
* The pre-processing is performed by {@code combiner}, a second method handle.
* Of the arguments passed to the adapter, the first {@code N} arguments
* are copied to the combiner, which is then called.
* (Here, {@code N} is defined as the parameter count of the combiner.)
* After this, control passes to the target, with any result
* from the combiner inserted before the original {@code N} incoming
* arguments.
*
* If the combiner returns a value, the first parameter type of the target
* must be identical with the return type of the combiner, and the next
* {@code N} parameter types of the target must exactly match the parameters
* of the combiner.
*
* If the combiner has a void return, no result will be inserted,
* and the first {@code N} parameter types of the target
* must exactly match the parameters of the combiner.
*
* The resulting adapter is the same type as the target, except that the
* first parameter type is dropped,
* if it corresponds to the result of the combiner.
*
* (Note that {@link #dropArguments(MethodHandle,int,List) dropArguments} can be used to remove any arguments
* that either the combiner or the target does not wish to receive.
* If some of the incoming arguments are destined only for the combiner,
* consider using {@link MethodHandle#asCollector asCollector} instead, since those
* arguments will not need to be live on the stack on entry to the
* target.)
* Example:
* Here is pseudocode for the resulting adapter:
* Here is pseudocode for the resulting adapter:
*
* The target and handler must have the same corresponding
* argument and return types, except that handler may omit trailing arguments
* (similarly to the predicate in {@link #guardWithTest guardWithTest}).
* Also, the handler must have an extra leading parameter of {@code exType} or a supertype.
* Here is pseudocode for the resulting adapter:
*
* The target and handler must return the same type, even if the handler
* always throws. (This might happen, for instance, because the handler
* is simulating a {@code finally} clause).
* To create such a throwing handler, compose the handler creation logic
* with {@link #throwException throwException},
* in order to create a method handle of the correct return type.
* @param target method handle to call
* @param exType the type of exception which the handler will catch
* @param handler method handle to call if a matching exception is thrown
* @return method handle which incorporates the specified try/catch logic
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if {@code handler} does not accept
* the given exception type, or if the method handle types do
* not match in their return types and their
* corresponding parameters
*/
public static
MethodHandle catchException(MethodHandle target,
Class exType,
MethodHandle handler) {
MethodType ttype = target.type();
MethodType htype = handler.type();
if (htype.parameterCount() < 1 ||
!htype.parameterType(0).isAssignableFrom(exType))
throw newIllegalArgumentException("handler does not accept exception type "+exType);
if (htype.returnType() != ttype.returnType())
throw misMatchedTypes("target and handler return types", ttype, htype);
ListLookup Factory Methods
* The factory methods on a {@code Lookup} object correspond to all major
* use cases for methods, constructors, and fields.
* Each method handle created by a factory method is the functional
* equivalent of a particular bytecode behavior.
* (Bytecode behaviors are described in section 5.4.3.5 of the Java Virtual Machine Specification.)
* Here is a summary of the correspondence between these factory methods and
* the behavior the resulting method handles:
*
*
*
* Access checking
* Access checks are applied in the factory methods of {@code Lookup},
* when a method handle is created.
* This is a key difference from the Core Reflection API, since
* {@link java.lang.reflect.Method#invoke java.lang.reflect.Method.invoke}
* performs access checking against every caller, on every call.
*
*
*
*
* Security manager interactions
* Although bytecode instructions can only refer to classes in
* a related class loader, this API can search for methods in any
* class, as long as a reference to its {@code Class} object is
* available. Such cross-loader references are also possible with the
* Core Reflection API, and are impossible to bytecode instructions
* such as {@code invokestatic} or {@code getfield}.
* There is a {@linkplain java.lang.SecurityManager security manager API}
* to allow applications to check such cross-loader references.
* These checks apply to both the {@code MethodHandles.Lookup} API
* and the Core Reflection API
* (as found on {@link java.lang.Class Class}).
*
*
* Security checks are performed after other access checks have passed.
* Therefore, the above rules presuppose a member that is public,
* or else that is being accessed from a lookup class that has
* rights to access the member.
*
* Caller sensitive methods
* A small number of Java methods have a special property called caller sensitivity.
* A caller-sensitive method can behave differently depending on the
* identity of its immediate caller.
*
*
*
* @param requestedLookupClass the desired lookup class for the new lookup object
* @return a lookup object which reports the desired lookup class
* @throws NullPointerException if the argument is null
*/
public Lookup in(Class requestedLookupClass) {
requestedLookupClass.getClass(); // null check
// Android-changed: There's no notion of a trusted lookup.
// if (allowedModes == TRUSTED) // IMPL_LOOKUP can make any lookup at all
// return new Lookup(requestedLookupClass, ALL_MODES);
if (requestedLookupClass == this.lookupClass)
return this; // keep same capabilities
int newModes = (allowedModes & (ALL_MODES & ~PROTECTED));
if ((newModes & PACKAGE) != 0
&& !VerifyAccess.isSamePackage(this.lookupClass, requestedLookupClass)) {
newModes &= ~(PACKAGE|PRIVATE);
}
// Allow nestmate lookups to be created without special privilege:
if ((newModes & PRIVATE) != 0
&& !VerifyAccess.isSamePackageMember(this.lookupClass, requestedLookupClass)) {
newModes &= ~PRIVATE;
}
if ((newModes & PUBLIC) != 0
&& !VerifyAccess.isClassAccessible(requestedLookupClass, this.lookupClass, allowedModes)) {
// The requested class it not accessible from the lookup class.
// No permissions.
newModes = 0;
}
checkUnprivilegedlookupClass(requestedLookupClass, newModes);
return new Lookup(requestedLookupClass, newModes);
}
// Make sure outer class is initialized first.
//
// Android-changed: Removed unnecessary reference to IMPL_NAMES.
// static { IMPL_NAMES.getClass(); }
/** Version of lookup which is trusted minimally.
* It can only be used to create method handles to
* publicly accessible members.
*/
static final Lookup PUBLIC_LOOKUP = new Lookup(Object.class, PUBLIC);
/** Package-private version of lookup which is trusted. */
static final Lookup IMPL_LOOKUP = new Lookup(Object.class, ALL_MODES);
private static void checkUnprivilegedlookupClass(Class lookupClass, int allowedModes) {
String name = lookupClass.getName();
if (name.startsWith("java.lang.invoke."))
throw newIllegalArgumentException("illegal lookupClass: "+lookupClass);
// For caller-sensitive MethodHandles.lookup()
// disallow lookup more restricted packages
//
// Android-changed: The bootstrap classloader isn't null.
if (allowedModes == ALL_MODES &&
lookupClass.getClassLoader() == Object.class.getClassLoader()) {
if (name.startsWith("java.") ||
(name.startsWith("sun.")
&& !name.startsWith("sun.invoke.")
&& !name.equals("sun.reflect.ReflectionFactory"))) {
throw newIllegalArgumentException("illegal lookupClass: " + lookupClass);
}
}
}
/**
* Displays the name of the class from which lookups are to be made.
* (The name is the one reported by {@link java.lang.Class#getName() Class.getName}.)
* If there are restrictions on the access permitted to this lookup,
* this is indicated by adding a suffix to the class name, consisting
* of a slash and a keyword. The keyword represents the strongest
* allowed access, and is chosen as follows:
*
*
* If none of the above cases apply, it is the case that full
* access (public, package, private, and protected) is allowed.
* In this case, no suffix is added.
* This is true only of an object obtained originally from
* {@link java.lang.invoke.MethodHandles#lookup MethodHandles.lookup}.
* Objects created by {@link java.lang.invoke.MethodHandles.Lookup#in Lookup.in}
* always have restricted access, and will display a suffix.
*
* @param refc the class from which the method is accessed
* @param name the name of the method
* @param type the type of the method
* @return the desired method handle
* @throws NoSuchMethodException if the method does not exist
* @throws IllegalAccessException if access checking fails,
* or if the method is not {@code static},
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public
MethodHandle findStatic(Class refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
Method method = refc.getDeclaredMethod(name, type.ptypes());
final int modifiers = method.getModifiers();
if (!Modifier.isStatic(modifiers)) {
throw new IllegalAccessException("Method" + method + " is not static");
}
checkReturnType(method, type);
checkAccess(refc, method.getDeclaringClass(), modifiers, method.getName());
return createMethodHandle(method, MethodHandle.INVOKE_STATIC, type);
}
private MethodHandle findVirtualForMH(String name, MethodType type) {
// these names require special lookups because of the implicit MethodType argument
if ("invoke".equals(name))
return invoker(type);
if ("invokeExact".equals(name))
return exactInvoker(type);
return null;
}
private static MethodHandle createMethodHandle(Method method, int handleKind,
MethodType methodType) {
MethodHandle mh = new MethodHandleImpl(method.getArtMethod(), handleKind, methodType);
if (method.isVarArgs()) {
return new Transformers.VarargsCollector(mh);
} else {
return mh;
}
}
/**
* Produces a method handle for a virtual method.
* The type of the method handle will be that of the method,
* with the receiver type (usually {@code refc}) prepended.
* The method and all its argument types must be accessible to the lookup object.
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle MH_asList = publicLookup().findStatic(Arrays.class,
"asList", methodType(List.class, Object[].class));
assertEquals("[x, y]", MH_asList.invoke("x", "y").toString());
* }
*
* @param refc the class or interface from which the method is accessed
* @param name the name of the method
* @param type the type of the method, with the receiver argument omitted
* @return the desired method handle
* @throws NoSuchMethodException if the method does not exist
* @throws IllegalAccessException if access checking fails,
* or if the method is {@code static}
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findVirtual(Class refc, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
// Special case : when we're looking up a virtual method on the MethodHandles class
// itself, we can return one of our specialized invokers.
if (refc == MethodHandle.class) {
MethodHandle mh = findVirtualForMH(name, type);
if (mh != null) {
return mh;
}
}
Method method = refc.getInstanceMethod(name, type.ptypes());
if (method == null) {
// This is pretty ugly and a consequence of the MethodHandles API. We have to throw
// an IAE and not an NSME if the method exists but is static (even though the RI's
// IAE has a message that says "no such method"). We confine the ugliness and
// slowness to the failure case, and allow getInstanceMethod to remain fairly
// general.
try {
Method m = refc.getDeclaredMethod(name, type.ptypes());
if (Modifier.isStatic(m.getModifiers())) {
throw new IllegalAccessException("Method" + m + " is static");
}
} catch (NoSuchMethodException ignored) {
}
throw new NoSuchMethodException(name + " " + Arrays.toString(type.ptypes()));
}
checkReturnType(method, type);
// We have a valid method, perform access checks.
checkAccess(refc, method.getDeclaringClass(), method.getModifiers(), method.getName());
// Insert the leading reference parameter.
MethodType handleType = type.insertParameterTypes(0, refc);
return createMethodHandle(method, MethodHandle.INVOKE_VIRTUAL, handleType);
}
/**
* Produces a method handle which creates an object and initializes it, using
* the constructor of the specified type.
* The parameter types of the method handle will be those of the constructor,
* while the return type will be a reference to the constructor's class.
* The constructor and all its argument types must be accessible to the lookup object.
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle MH_concat = publicLookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
MethodHandle MH_hashCode = publicLookup().findVirtual(Object.class,
"hashCode", methodType(int.class));
MethodHandle MH_hashCode_String = publicLookup().findVirtual(String.class,
"hashCode", methodType(int.class));
assertEquals("xy", (String) MH_concat.invokeExact("x", "y"));
assertEquals("xy".hashCode(), (int) MH_hashCode.invokeExact((Object)"xy"));
assertEquals("xy".hashCode(), (int) MH_hashCode_String.invokeExact("xy"));
// interface method:
MethodHandle MH_subSequence = publicLookup().findVirtual(CharSequence.class,
"subSequence", methodType(CharSequence.class, int.class, int.class));
assertEquals("def", MH_subSequence.invoke("abcdefghi", 3, 6).toString());
// constructor "internal method" must be accessed differently:
MethodType MT_newString = methodType(void.class); //()V for new String()
try { assertEquals("impossible", lookup()
.findVirtual(String.class, "
* @param refc the class or interface from which the method is accessed
* @param type the type of the method, with the receiver argument omitted, and a void return type
* @return the desired method handle
* @throws NoSuchMethodException if the constructor does not exist
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findConstructor(Class refc, MethodType type) throws NoSuchMethodException, IllegalAccessException {
if (refc.isArray()) {
throw new NoSuchMethodException("no constructor for array class: " + refc.getName());
}
// The queried |type| is (PT1,PT2,..)V
Constructor constructor = refc.getDeclaredConstructor(type.ptypes());
if (constructor == null) {
throw new NoSuchMethodException(
"No constructor for " + constructor.getDeclaringClass() + " matching " + type);
}
checkAccess(refc, constructor.getDeclaringClass(), constructor.getModifiers(),
constructor.getName());
return createMethodHandleForConstructor(constructor);
}
private MethodHandle createMethodHandleForConstructor(Constructor constructor) {
Class refc = constructor.getDeclaringClass();
MethodType constructorType =
MethodType.methodType(refc, constructor.getParameterTypes());
MethodHandle mh;
if (refc == String.class) {
// String constructors have optimized StringFactory methods
// that matches returned type. These factory methods combine the
// memory allocation and initialization calls for String objects.
mh = new MethodHandleImpl(constructor.getArtMethod(), MethodHandle.INVOKE_DIRECT,
constructorType);
} else {
// Constructors for all other classes use a Construct transformer to perform
// their memory allocation and call to {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle MH_newArrayList = publicLookup().findConstructor(
ArrayList.class, methodType(void.class, Collection.class));
Collection orig = Arrays.asList("x", "y");
Collection copy = (ArrayList) MH_newArrayList.invokeExact(orig);
assert(orig != copy);
assertEquals(orig, copy);
// a variable-arity constructor:
MethodHandle MH_newProcessBuilder = publicLookup().findConstructor(
ProcessBuilder.class, methodType(void.class, String[].class));
ProcessBuilder pb = (ProcessBuilder)
MH_newProcessBuilder.invoke("x", "y", "z");
assertEquals("[x, y, z]", pb.command().toString());
* }
*
* @param refc the class or interface from which the method is accessed
* @param name the name of the method (which must not be "<init>")
* @param type the type of the method, with the receiver argument omitted
* @param specialCaller the proposed calling class to perform the {@code invokespecial}
* @return the desired method handle
* @throws NoSuchMethodException if the method does not exist
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findSpecial(Class refc, String name, MethodType type,
Class specialCaller) throws NoSuchMethodException, IllegalAccessException {
if (specialCaller == null) {
throw new NullPointerException("specialCaller == null");
}
if (type == null) {
throw new NullPointerException("type == null");
}
if (name == null) {
throw new NullPointerException("name == null");
}
if (refc == null) {
throw new NullPointerException("ref == null");
}
// Make sure that the special caller is identical to the lookup class or that we have
// private access.
checkSpecialCaller(specialCaller);
// Even though constructors are invoked using a "special" invoke, handles to them can't
// be created using findSpecial. Callers must use findConstructor instead. Similarly,
// there is no path for calling static class initializers.
if (name.startsWith("<")) {
throw new NoSuchMethodException(name + " is not a valid method name.");
}
Method method = refc.getDeclaredMethod(name, type.ptypes());
checkReturnType(method, type);
return findSpecial(method, type, refc, specialCaller);
}
private MethodHandle findSpecial(Method method, MethodType type,
Class refc, Class specialCaller)
throws IllegalAccessException {
if (Modifier.isStatic(method.getModifiers())) {
throw new IllegalAccessException("expected a non-static method:" + method);
}
if (Modifier.isPrivate(method.getModifiers())) {
// Since this is a private method, we'll need to also make sure that the
// lookup class is the same as the refering class. We've already checked that
// the specialCaller is the same as the special lookup class, both of these must
// be the same as the declaring class(*) in order to access the private method.
//
// (*) Well, this isn't true for nested classes but OpenJDK doesn't support those
// either.
if (refc != lookupClass()) {
throw new IllegalAccessException("no private access for invokespecial : "
+ refc + ", from" + this);
}
// This is a private method, so there's nothing special to do.
MethodType handleType = type.insertParameterTypes(0, refc);
return createMethodHandle(method, MethodHandle.INVOKE_DIRECT, handleType);
}
// This is a public, protected or package-private method, which means we're expecting
// invoke-super semantics. We'll have to restrict the receiver type appropriately on the
// handle once we check that there really is a "super" relationship between them.
if (!method.getDeclaringClass().isAssignableFrom(specialCaller)) {
throw new IllegalAccessException(refc + "is not assignable from " + specialCaller);
}
// Note that we restrict the receiver to "specialCaller" instances.
MethodType handleType = type.insertParameterTypes(0, specialCaller);
return createMethodHandle(method, MethodHandle.INVOKE_SUPER, handleType);
}
/**
* Produces a method handle giving read access to a non-static field.
* The type of the method handle will have a return type of the field's
* value type.
* The method handle's single argument will be the instance containing
* the field.
* Access checking is performed immediately on behalf of the lookup class.
* @param refc the class or interface from which the method is accessed
* @param name the field's name
* @param type the field's type
* @return a method handle which can load values from the field
* @throws NoSuchFieldException if the field does not exist
* @throws IllegalAccessException if access checking fails, or if the field is {@code static}
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findGetter(Class refc, String name, Class type) throws NoSuchFieldException, IllegalAccessException {
return findAccessor(refc, name, type, MethodHandle.IGET);
}
private MethodHandle findAccessor(Class refc, String name, Class type, int kind)
throws NoSuchFieldException, IllegalAccessException {
final Field field = refc.getDeclaredField(name);
final Class fieldType = field.getType();
if (fieldType != type) {
throw new NoSuchFieldException(
"Field has wrong type: " + fieldType + " != " + type);
}
return findAccessor(field, refc, type, kind, true /* performAccessChecks */);
}
private MethodHandle findAccessor(Field field, Class refc, Class fieldType, int kind,
boolean performAccessChecks)
throws IllegalAccessException {
if (!performAccessChecks) {
checkAccess(refc, field.getDeclaringClass(), field.getModifiers(), field.getName());
}
final boolean isStaticKind = kind == MethodHandle.SGET || kind == MethodHandle.SPUT;
final int modifiers = field.getModifiers();
if (Modifier.isStatic(modifiers) != isStaticKind) {
String reason = "Field " + field + " is " +
(isStaticKind ? "not " : "") + "static";
throw new IllegalAccessException(reason);
}
final boolean isSetterKind = kind == MethodHandle.IPUT || kind == MethodHandle.SPUT;
if (Modifier.isFinal(modifiers) && isSetterKind) {
throw new IllegalAccessException("Field " + field + " is final");
}
final MethodType methodType;
switch (kind) {
case MethodHandle.SGET:
methodType = MethodType.methodType(fieldType);
break;
case MethodHandle.SPUT:
methodType = MethodType.methodType(void.class, fieldType);
break;
case MethodHandle.IGET:
methodType = MethodType.methodType(fieldType, refc);
break;
case MethodHandle.IPUT:
methodType = MethodType.methodType(void.class, refc, fieldType);
break;
default:
throw new IllegalArgumentException("Invalid kind " + kind);
}
return new MethodHandleImpl(field.getArtField(), kind, methodType);
}
/**
* Produces a method handle giving write access to a non-static field.
* The type of the method handle will have a void return type.
* The method handle will take two arguments, the instance containing
* the field, and the value to be stored.
* The second argument will be of the field's value type.
* Access checking is performed immediately on behalf of the lookup class.
* @param refc the class or interface from which the method is accessed
* @param name the field's name
* @param type the field's type
* @return a method handle which can store values into the field
* @throws NoSuchFieldException if the field does not exist
* @throws IllegalAccessException if access checking fails, or if the field is {@code static}
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
*/
public MethodHandle findSetter(Class refc, String name, Class type) throws NoSuchFieldException, IllegalAccessException {
return findAccessor(refc, name, type, MethodHandle.IPUT);
}
/**
* Produces a method handle giving read access to a static field.
* The type of the method handle will have a return type of the field's
* value type.
* The method handle will take no arguments.
* Access checking is performed immediately on behalf of the lookup class.
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
static class Listie extends ArrayList {
public String toString() { return "[wee Listie]"; }
static Lookup lookup() { return MethodHandles.lookup(); }
}
...
// no access to constructor via invokeSpecial:
MethodHandle MH_newListie = Listie.lookup()
.findConstructor(Listie.class, methodType(void.class));
Listie l = (Listie) MH_newListie.invokeExact();
try { assertEquals("impossible", Listie.lookup().findSpecial(
Listie.class, "
* where {@code defc} is either {@code receiver.getClass()} or a super
* type of that class, in which the requested method is accessible
* to the lookup class.
* (Note that {@code bindTo} does not preserve variable arity.)
* @param receiver the object from which the method is accessed
* @param name the name of the method
* @param type the type of the method, with the receiver argument omitted
* @return the desired method handle
* @throws NoSuchMethodException if the method does not exist
* @throws IllegalAccessException if access checking fails
* or if the method's variable arity modifier bit
* is set and {@code asVarargsCollector} fails
* @exception SecurityException if a security manager is present and it
* refuses access
* @throws NullPointerException if any argument is null
* @see MethodHandle#bindTo
* @see #findVirtual
*/
public MethodHandle bind(Object receiver, String name, MethodType type) throws NoSuchMethodException, IllegalAccessException {
MethodHandle handle = findVirtual(receiver.getClass(), name, type);
MethodHandle adapter = handle.bindTo(receiver);
MethodType adapterType = adapter.type();
if (handle.isVarargsCollector()) {
adapter = adapter.asVarargsCollector(
adapterType.parameterType(adapterType.parameterCount() - 1));
}
return adapter;
}
/**
* Makes a direct method handle
* to m, if the lookup class has permission.
* If m is non-static, the receiver argument is treated as an initial argument.
* If m is virtual, overriding is respected on every call.
* Unlike the Core Reflection API, exceptions are not wrapped.
* The type of the method handle will be that of the method,
* with the receiver type prepended (but only if it is non-static).
* If the method's {@code accessible} flag is not set,
* access checking is performed immediately on behalf of the lookup class.
* If m is not public, do not share the resulting handle with untrusted parties.
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle mh0 = lookup().findVirtual(defc, name, type);
MethodHandle mh1 = mh0.bindTo(receiver);
MethodType mt1 = mh1.type();
if (mh0.isVarargsCollector())
mh1 = mh1.asVarargsCollector(mt1.parameterType(mt1.parameterCount()-1));
return mh1;
* }
*
*
* This method throws no reflective or security exceptions.
* @param type the desired target type
* @param leadingArgCount number of fixed arguments, to be passed unchanged to the target
* @return a method handle suitable for invoking any method handle of the given type
* @throws NullPointerException if {@code type} is null
* @throws IllegalArgumentException if {@code leadingArgCount} is not in
* the range from 0 to {@code type.parameterCount()} inclusive,
* or if the resulting method handle's type would have
* too many parameters
*/
static public
MethodHandle spreadInvoker(MethodType type, int leadingArgCount) {
if (leadingArgCount < 0 || leadingArgCount > type.parameterCount())
throw newIllegalArgumentException("bad argument count", leadingArgCount);
MethodHandle invoker = MethodHandles.invoker(type);
int spreadArgCount = type.parameterCount() - leadingArgCount;
invoker = invoker.asSpreader(Object[].class, spreadArgCount);
return invoker;
}
/**
* Produces a special invoker method handle which can be used to
* invoke any method handle of the given type, as if by {@link MethodHandle#invokeExact invokeExact}.
* The resulting invoker will have a type which is
* exactly equal to the desired type, except that it will accept
* an additional leading argument of type {@code MethodHandle}.
* {@code
MethodHandle invoker = MethodHandles.invoker(type);
int spreadArgCount = type.parameterCount() - leadingArgCount;
invoker = invoker.asSpreader(Object[].class, spreadArgCount);
return invoker;
* }
*
* @param target the method handle to invoke after arguments are retyped
* @param newType the expected type of the new method handle
* @return a method handle which delegates to the target after performing
* any necessary argument conversions, and arranges for any
* necessary return value conversions
* @throws NullPointerException if either argument is null
* @throws WrongMethodTypeException if the conversion cannot be made
* @see MethodHandle#asType
*/
public static
MethodHandle explicitCastArguments(MethodHandle target, MethodType newType) {
explicitCastArgumentsChecks(target, newType);
// use the asTypeCache when possible:
MethodType oldType = target.type();
if (oldType == newType) return target;
if (oldType.explicitCastEquivalentToAsType(newType)) {
return target.asFixedArity().asType(newType);
}
return new Transformers.ExplicitCastArguments(target, newType);
}
private static void explicitCastArgumentsChecks(MethodHandle target, MethodType newType) {
if (target.type().parameterCount() != newType.parameterCount()) {
throw new WrongMethodTypeException("cannot explicitly cast " + target + " to " + newType);
}
}
/**
* Produces a method handle which adapts the calling sequence of the
* given method handle to a new type, by reordering the arguments.
* The resulting method handle is guaranteed to report a type
* which is equal to the desired new type.
*
* @param target the method handle to invoke after arguments are reordered
* @param newType the expected type of the new method handle
* @param reorder an index array which controls the reordering
* @return a method handle which delegates to the target after it
* drops unused arguments and moves and/or duplicates the other arguments
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if the index array length is not equal to
* the arity of the target, or if any index array element
* not a valid index for a parameter of {@code newType},
* or if two corresponding parameter types in
* {@code target.type()} and {@code newType} are not identical,
*/
public static
MethodHandle permuteArguments(MethodHandle target, MethodType newType, int... reorder) {
reorder = reorder.clone(); // get a private copy
MethodType oldType = target.type();
permuteArgumentChecks(reorder, newType, oldType);
return new Transformers.PermuteArguments(newType, target, reorder);
}
// Android-changed: findFirstDupOrDrop is unused and removed.
// private static int findFirstDupOrDrop(int[] reorder, int newArity);
private static boolean permuteArgumentChecks(int[] reorder, MethodType newType, MethodType oldType) {
if (newType.returnType() != oldType.returnType())
throw newIllegalArgumentException("return types do not match",
oldType, newType);
if (reorder.length == oldType.parameterCount()) {
int limit = newType.parameterCount();
boolean bad = false;
for (int j = 0; j < reorder.length; j++) {
int i = reorder[j];
if (i < 0 || i >= limit) {
bad = true; break;
}
Class src = newType.parameterType(i);
Class dst = oldType.parameterType(j);
if (src != dst)
throw newIllegalArgumentException("parameter types do not match after reorder",
oldType, newType);
}
if (!bad) return true;
}
throw newIllegalArgumentException("bad reorder array: "+Arrays.toString(reorder));
}
/**
* Produces a method handle of the requested return type which returns the given
* constant value every time it is invoked.
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodType intfn1 = methodType(int.class, int.class);
MethodType intfn2 = methodType(int.class, int.class, int.class);
MethodHandle sub = ... (int x, int y) -> (x-y) ...;
assert(sub.type().equals(intfn2));
MethodHandle sub1 = permuteArguments(sub, intfn2, 0, 1);
MethodHandle rsub = permuteArguments(sub, intfn2, 1, 0);
assert((int)rsub.invokeExact(1, 100) == 99);
MethodHandle add = ... (int x, int y) -> (x+y) ...;
assert(add.type().equals(intfn2));
MethodHandle twice = permuteArguments(add, intfn1, 0, 0);
assert(twice.type().equals(intfn1));
assert((int)twice.invokeExact(21) == 42);
* }
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodType bigType = cat.type().insertParameterTypes(0, int.class, String.class);
MethodHandle d0 = dropArguments(cat, 0, bigType.parameterList().subList(0,2));
assertEquals(bigType, d0.type());
assertEquals("yz", (String) d0.invokeExact(123, "x", "y", "z"));
* }
* @param target the method handle to invoke after the arguments are dropped
* @param valueTypes the type(s) of the argument(s) to drop
* @param pos position of first argument to drop (zero for the leftmost)
* @return a method handle which drops arguments of the given types,
* before calling the original method handle
* @throws NullPointerException if the target is null,
* or if the {@code valueTypes} list or any of its elements is null
* @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
* or if {@code pos} is negative or greater than the arity of the target,
* or if the new method handle's type would have too many parameters
*/
public static
MethodHandle dropArguments(MethodHandle target, int pos, List
* {@link #dropArguments(MethodHandle,int,Class...) dropArguments}{@code (target, pos, valueTypes.toArray(new Class[0]))}
*
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodHandle d0 = dropArguments(cat, 0, String.class);
assertEquals("yz", (String) d0.invokeExact("x", "y", "z"));
MethodHandle d1 = dropArguments(cat, 1, String.class);
assertEquals("xz", (String) d1.invokeExact("x", "y", "z"));
MethodHandle d2 = dropArguments(cat, 2, String.class);
assertEquals("xy", (String) d2.invokeExact("x", "y", "z"));
MethodHandle d12 = dropArguments(cat, 1, int.class, boolean.class);
assertEquals("xz", (String) d12.invokeExact("x", 12, true, "z"));
* }
* @param target the method handle to invoke after the arguments are dropped
* @param valueTypes the type(s) of the argument(s) to drop
* @param pos position of first argument to drop (zero for the leftmost)
* @return a method handle which drops arguments of the given types,
* before calling the original method handle
* @throws NullPointerException if the target is null,
* or if the {@code valueTypes} array or any of its elements is null
* @throws IllegalArgumentException if any element of {@code valueTypes} is {@code void.class},
* or if {@code pos} is negative or greater than the arity of the target,
* or if the new method handle's type would have
* too many parameters
*/
public static
MethodHandle dropArguments(MethodHandle target, int pos, Class... valueTypes) {
return dropArguments(target, pos, Arrays.asList(valueTypes));
}
/**
* Adapts a target method handle by pre-processing
* one or more of its arguments, each with its own unary filter function,
* and then calling the target with each pre-processed argument
* replaced by the result of its corresponding filter function.
*
* {@link #dropArguments(MethodHandle,int,List) dropArguments}{@code (target, pos, Arrays.asList(valueTypes))}
*
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
MethodHandle upcase = lookup().findVirtual(String.class,
"toUpperCase", methodType(String.class));
assertEquals("xy", (String) cat.invokeExact("x", "y"));
MethodHandle f0 = filterArguments(cat, 0, upcase);
assertEquals("Xy", (String) f0.invokeExact("x", "y")); // Xy
MethodHandle f1 = filterArguments(cat, 1, upcase);
assertEquals("xY", (String) f1.invokeExact("x", "y")); // xY
MethodHandle f2 = filterArguments(cat, 0, upcase, upcase);
assertEquals("XY", (String) f2.invokeExact("x", "y")); // XY
* }
*
* @param target the method handle to invoke after arguments are filtered
* @param pos the position of the first argument to filter
* @param filters method handles to call initially on filtered arguments
* @return method handle which incorporates the specified argument filtering logic
* @throws NullPointerException if the target is null
* or if the {@code filters} array is null
* @throws IllegalArgumentException if a non-null element of {@code filters}
* does not match a corresponding argument type of target as described above,
* or if the {@code pos+filters.length} is greater than {@code target.type().parameterCount()},
* or if the resulting method handle's type would have
* too many parameters
*/
public static
MethodHandle filterArguments(MethodHandle target, int pos, MethodHandle... filters) {
filterArgumentsCheckArity(target, pos, filters);
for (int i = 0; i < filters.length; ++i) {
filterArgumentChecks(target, i + pos, filters[i]);
}
return new Transformers.FilterArguments(target, pos, filters);
}
private static void filterArgumentsCheckArity(MethodHandle target, int pos, MethodHandle[] filters) {
MethodType targetType = target.type();
int maxPos = targetType.parameterCount();
if (pos + filters.length > maxPos)
throw newIllegalArgumentException("too many filters");
}
private static void filterArgumentChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
MethodType targetType = target.type();
MethodType filterType = filter.type();
if (filterType.parameterCount() != 1
|| filterType.returnType() != targetType.parameterType(pos))
throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
}
/**
* Adapts a target method handle by pre-processing
* a sub-sequence of its arguments with a filter (another method handle).
* The pre-processed arguments are replaced by the result (if any) of the
* filter function.
* The target is then called on the modified (usually shortened) argument list.
* {@code
* V target(P... p, A[i]... a[i], B... b);
* A[i] filter[i](V[i]);
* T adapter(P... p, V[i]... v[i], B... b) {
* return target(p..., f[i](v[i])..., b...);
* }
* }
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle deepToString = publicLookup()
.findStatic(Arrays.class, "deepToString", methodType(String.class, Object[].class));
MethodHandle ts1 = deepToString.asCollector(String[].class, 1);
assertEquals("[strange]", (String) ts1.invokeExact("strange"));
MethodHandle ts2 = deepToString.asCollector(String[].class, 2);
assertEquals("[up, down]", (String) ts2.invokeExact("up", "down"));
MethodHandle ts3 = deepToString.asCollector(String[].class, 3);
MethodHandle ts3_ts2 = collectArguments(ts3, 1, ts2);
assertEquals("[top, [up, down], strange]",
(String) ts3_ts2.invokeExact("top", "up", "down", "strange"));
MethodHandle ts3_ts2_ts1 = collectArguments(ts3_ts2, 3, ts1);
assertEquals("[top, [up, down], [strange]]",
(String) ts3_ts2_ts1.invokeExact("top", "up", "down", "strange"));
MethodHandle ts3_ts2_ts3 = collectArguments(ts3_ts2, 1, ts3);
assertEquals("[top, [[up, down, strange], charm], bottom]",
(String) ts3_ts2_ts3.invokeExact("top", "up", "down", "strange", "charm", "bottom"));
* }
* {@code
* T target(A...,V,C...);
* V filter(B...);
* T adapter(A... a,B... b,C... c) {
* V v = filter(b...);
* return target(a...,v,c...);
* }
* // and if the filter has no arguments:
* T target2(A...,V,C...);
* V filter2();
* T adapter2(A... a,C... c) {
* V v = filter2();
* return target2(a...,v,c...);
* }
* // and if the filter has a void return:
* T target3(A...,C...);
* void filter3(B...);
* void adapter3(A... a,B... b,C... c) {
* filter3(b...);
* return target3(a...,c...);
* }
* }
* If the target method handle consumes no arguments besides than the result
* (if any) of the filter {@code coll}, then {@code collectArguments(mh, 0, coll)}
* is equivalent to {@code filterReturnValue(coll, mh)}.
* If the filter method handle {@code coll} consumes one argument and produces
* a non-void result, then {@code collectArguments(mh, N, coll)}
* is equivalent to {@code filterArguments(mh, N, coll)}.
* Other equivalences are possible but would require argument permutation.
*
* @param target the method handle to invoke after filtering the subsequence of arguments
* @param pos the position of the first adapter argument to pass to the filter,
* and/or the target argument which receives the result of the filter
* @param filter method handle to call on the subsequence of arguments
* @return method handle which incorporates the specified argument subsequence filtering logic
* @throws NullPointerException if either argument is null
* @throws IllegalArgumentException if the return type of {@code filter}
* is non-void and is not the same as the {@code pos} argument of the target,
* or if {@code pos} is not between 0 and the target's arity, inclusive,
* or if the resulting method handle's type would have
* too many parameters
* @see MethodHandles#foldArguments
* @see MethodHandles#filterArguments
* @see MethodHandles#filterReturnValue
*/
public static
MethodHandle collectArguments(MethodHandle target, int pos, MethodHandle filter) {
MethodType newType = collectArgumentsChecks(target, pos, filter);
return new Transformers.CollectArguments(target, filter, pos, newType);
}
private static MethodType collectArgumentsChecks(MethodHandle target, int pos, MethodHandle filter) throws RuntimeException {
MethodType targetType = target.type();
MethodType filterType = filter.type();
Class rtype = filterType.returnType();
List{@code
* mh = MethodHandles.dropArguments(mh, 1, coll.type().parameterList()); //step 2
* mh = MethodHandles.foldArguments(mh, coll); //step 1
* }
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle cat = lookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
MethodHandle length = lookup().findVirtual(String.class,
"length", methodType(int.class));
System.out.println((String) cat.invokeExact("x", "y")); // xy
MethodHandle f0 = filterReturnValue(cat, length);
System.out.println((int) f0.invokeExact("x", "y")); // 2
* }
* @param target the method handle to invoke before filtering the return value
* @param filter method handle to call on the return value
* @return method handle which incorporates the specified return value filtering logic
* @throws NullPointerException if either argument is null
* @throws IllegalArgumentException if the argument list of {@code filter}
* does not match the return type of target as described above
*/
public static
MethodHandle filterReturnValue(MethodHandle target, MethodHandle filter) {
MethodType targetType = target.type();
MethodType filterType = filter.type();
filterReturnValueChecks(targetType, filterType);
return new Transformers.FilterReturnValue(target, filter);
}
private static void filterReturnValueChecks(MethodType targetType, MethodType filterType) throws RuntimeException {
Class rtype = targetType.returnType();
int filterValues = filterType.parameterCount();
if (filterValues == 0
? (rtype != void.class)
: (rtype != filterType.parameterType(0) || filterValues != 1))
throw newIllegalArgumentException("target and filter types do not match", targetType, filterType);
}
/**
* Adapts a target method handle by pre-processing
* some of its arguments, and then calling the target with
* the result of the pre-processing, inserted into the original
* sequence of arguments.
* {@code
* V target(A...);
* T filter(V);
* T adapter(A... a) {
* V v = target(a...);
* return filter(v);
* }
* // and if the target has a void return:
* void target2(A...);
* T filter2();
* T adapter2(A... a) {
* target2(a...);
* return filter2();
* }
* // and if the filter has a void return:
* V target3(A...);
* void filter3(V);
* void adapter3(A... a) {
* V v = target3(a...);
* filter3(v);
* }
* }
* {@code
import static java.lang.invoke.MethodHandles.*;
import static java.lang.invoke.MethodType.*;
...
MethodHandle trace = publicLookup().findVirtual(java.io.PrintStream.class,
"println", methodType(void.class, String.class))
.bindTo(System.out);
MethodHandle cat = lookup().findVirtual(String.class,
"concat", methodType(String.class, String.class));
assertEquals("boojum", (String) cat.invokeExact("boo", "jum"));
MethodHandle catTrace = foldArguments(cat, trace);
// also prints "boo":
assertEquals("boojum", (String) catTrace.invokeExact("boo", "jum"));
* }
* @param target the method handle to invoke after arguments are combined
* @param combiner method handle to call initially on the incoming arguments
* @return method handle which incorporates the specified argument folding logic
* @throws NullPointerException if either argument is null
* @throws IllegalArgumentException if {@code combiner}'s return type
* is non-void and not the same as the first argument type of
* the target, or if the initial {@code N} argument types
* of the target
* (skipping one matching the {@code combiner}'s return type)
* are not identical with the argument types of {@code combiner}
*/
public static
MethodHandle foldArguments(MethodHandle target, MethodHandle combiner) {
int foldPos = 0;
MethodType targetType = target.type();
MethodType combinerType = combiner.type();
Class rtype = foldArgumentChecks(foldPos, targetType, combinerType);
return new Transformers.FoldArguments(target, combiner);
}
private static Class foldArgumentChecks(int foldPos, MethodType targetType, MethodType combinerType) {
int foldArgs = combinerType.parameterCount();
Class rtype = combinerType.returnType();
int foldVals = rtype == void.class ? 0 : 1;
int afterInsertPos = foldPos + foldVals;
boolean ok = (targetType.parameterCount() >= afterInsertPos + foldArgs);
if (ok && !(combinerType.parameterList()
.equals(targetType.parameterList().subList(afterInsertPos,
afterInsertPos + foldArgs))))
ok = false;
if (ok && foldVals != 0 && combinerType.returnType() != targetType.parameterType(0))
ok = false;
if (!ok)
throw misMatchedTypes("target and combiner types", targetType, combinerType);
return rtype;
}
/**
* Makes a method handle which adapts a target method handle,
* by guarding it with a test, a boolean-valued method handle.
* If the guard fails, a fallback handle is called instead.
* All three method handles must have the same corresponding
* argument and return types, except that the return type
* of the test must be boolean, and the test is allowed
* to have fewer arguments than the other two method handles.
* {@code
* // there are N arguments in A...
* T target(V, A[N]..., B...);
* V combiner(A...);
* T adapter(A... a, B... b) {
* V v = combiner(a...);
* return target(v, a..., b...);
* }
* // and if the combiner has a void return:
* T target2(A[N]..., B...);
* void combiner2(A...);
* T adapter2(A... a, B... b) {
* combiner2(a...);
* return target2(a..., b...);
* }
* }
* Note that the test arguments ({@code a...} in the pseudocode) cannot
* be modified by execution of the test, and so are passed unchanged
* from the caller to the target or fallback as appropriate.
* @param test method handle used for test, must return boolean
* @param target method handle to call if test passes
* @param fallback method handle to call if test fails
* @return method handle which incorporates the specified if/then/else logic
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if {@code test} does not return boolean,
* or if all three method types do not match (with the return
* type of {@code test} changed to match that of the target).
*/
public static
MethodHandle guardWithTest(MethodHandle test,
MethodHandle target,
MethodHandle fallback) {
MethodType gtype = test.type();
MethodType ttype = target.type();
MethodType ftype = fallback.type();
if (!ttype.equals(ftype))
throw misMatchedTypes("target and fallback types", ttype, ftype);
if (gtype.returnType() != boolean.class)
throw newIllegalArgumentException("guard type is not a predicate "+gtype);
List{@code
* boolean test(A...);
* T target(A...,B...);
* T fallback(A...,B...);
* T adapter(A... a,B... b) {
* if (test(a...))
* return target(a..., b...);
* else
* return fallback(a..., b...);
* }
* }
* Note that the saved arguments ({@code a...} in the pseudocode) cannot
* be modified by execution of the target, and so are passed unchanged
* from the caller to the handler, if the handler is invoked.
* {@code
* T target(A..., B...);
* T handler(ExType, A...);
* T adapter(A... a, B... b) {
* try {
* return target(a..., b...);
* } catch (ExType ex) {
* return handler(ex, a...);
* }
* }
* }