/* * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang.invoke; import java.lang.reflect.*; import java.util.*; import java.lang.invoke.MethodHandles.Lookup; import static java.lang.invoke.MethodHandleStatics.*; /** * A symbolic reference obtained by cracking a direct method handle * into its consitutent symbolic parts. * To crack a direct method handle, call {@link Lookup#revealDirect Lookup.revealDirect}. *

Direct Method Handles

* A direct method handle represents a method, constructor, or field without * any intervening argument bindings or other transformations. * The method, constructor, or field referred to by a direct method handle is called * its underlying member. * Direct method handles may be obtained in any of these ways: * * *

Restrictions on Cracking

* Given a suitable {@code Lookup} object, it is possible to crack any direct method handle * to recover a symbolic reference for the underlying method, constructor, or field. * Cracking must be done via a {@code Lookup} object equivalent to that which created * the target method handle, or which has enough access permissions to recreate * an equivalent method handle. *

* If the underlying method is caller sensitive, * the direct method handle will have been "bound" to a particular caller class, the * {@linkplain java.lang.invoke.MethodHandles.Lookup#lookupClass() lookup class} * of the lookup object used to create it. * Cracking this method handle with a different lookup class will fail * even if the underlying method is public (like {@code Class.forName}). *

* The requirement of lookup object matching provides a "fast fail" behavior * for programs which may otherwise trust erroneous revelation of a method * handle with symbolic information (or caller binding) from an unexpected scope. * Use {@link java.lang.invoke.MethodHandles#reflectAs} to override this limitation. * *

Reference kinds

* The Lookup Factory Methods * correspond to all major use cases for methods, constructors, and fields. * These use cases may be distinguished using small integers as follows: * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
reference kinddescriptive namescopememberbehavior
{@code 1}{@code REF_getField}{@code class}{@code FT f;}{@code (T) this.f;}
{@code 2}{@code REF_getStatic}{@code class} or {@code interface}{@code static}
{@code FT f;}
{@code (T) C.f;}
{@code 3}{@code REF_putField}{@code class}{@code FT f;}{@code this.f = x;}
{@code 4}{@code REF_putStatic}{@code class}{@code static}
{@code FT f;}
{@code C.f = arg;}
{@code 5}{@code REF_invokeVirtual}{@code class}{@code T m(A*);}{@code (T) this.m(arg*);}
{@code 6}{@code REF_invokeStatic}{@code class} or {@code interface}{@code static}
{@code T m(A*);}
{@code (T) C.m(arg*);}
{@code 7}{@code REF_invokeSpecial}{@code class} or {@code interface}{@code T m(A*);}{@code (T) super.m(arg*);}
{@code 8}{@code REF_newInvokeSpecial}{@code class}{@code C(A*);}{@code new C(arg*);}
{@code 9}{@code REF_invokeInterface}{@code interface}{@code T m(A*);}{@code (T) this.m(arg*);}
* @since 1.8 */ public interface MethodHandleInfo { /** * A direct method handle reference kind, * as defined in the table above. */ // Android-changed: Inlined the values of these constants from MethodHandleNatives.Constants. public static final int REF_getField = 1, REF_getStatic = 2, REF_putField = 3, REF_putStatic = 4, REF_invokeVirtual = 5, REF_invokeStatic = 6, REF_invokeSpecial = 7, REF_newInvokeSpecial = 8, REF_invokeInterface = 9; /** * Returns the reference kind of the cracked method handle, which in turn * determines whether the method handle's underlying member was a constructor, method, or field. * See the table above for definitions. * @return the integer code for the kind of reference used to access the underlying member */ public int getReferenceKind(); /** * Returns the class in which the cracked method handle's underlying member was defined. * @return the declaring class of the underlying member */ public Class getDeclaringClass(); /** * Returns the name of the cracked method handle's underlying member. * This is {@code ""} if the underlying member was a constructor, * else it is a simple method name or field name. * @return the simple name of the underlying member */ public String getName(); /** * Returns the nominal type of the cracked symbolic reference, expressed as a method type. * If the reference is to a constructor, the return type will be {@code void}. * If it is to a non-static method, the method type will not mention the {@code this} parameter. * If it is to a field and the requested access is to read the field, * the method type will have no parameters and return the field type. * If it is to a field and the requested access is to write the field, * the method type will have one parameter of the field type and return {@code void}. *

* Note that original direct method handle may include a leading {@code this} parameter, * or (in the case of a constructor) will replace the {@code void} return type * with the constructed class. * The nominal type does not include any {@code this} parameter, * and (in the case of a constructor) will return {@code void}. * @return the type of the underlying member, expressed as a method type */ public MethodType getMethodType(); // Utility methods. // NOTE: class/name/type and reference kind constitute a symbolic reference // member and modifiers are an add-on, derived from Core Reflection (or the equivalent) /** * Reflects the underlying member as a method, constructor, or field object. * If the underlying member is public, it is reflected as if by * {@code getMethod}, {@code getConstructor}, or {@code getField}. * Otherwise, it is reflected as if by * {@code getDeclaredMethod}, {@code getDeclaredConstructor}, or {@code getDeclaredField}. * The underlying member must be accessible to the given lookup object. * @param the desired type of the result, either {@link Member} or a subtype * @param expected a class object representing the desired result type {@code T} * @param lookup the lookup object that created this MethodHandleInfo, or one with equivalent access privileges * @return a reference to the method, constructor, or field object * @exception ClassCastException if the member is not of the expected type * @exception NullPointerException if either argument is {@code null} * @exception IllegalArgumentException if the underlying member is not accessible to the given lookup object */ public T reflectAs(Class expected, Lookup lookup); /** * Returns the access modifiers of the underlying member. * @return the Java language modifiers for underlying member, * or -1 if the member cannot be accessed * @see Modifier * @see #reflectAs */ public int getModifiers(); /** * Determines if the underlying member was a variable arity method or constructor. * Such members are represented by method handles that are varargs collectors. * @implSpec * This produces a result equivalent to: *

{@code
     *     getReferenceKind() >= REF_invokeVirtual && Modifier.isTransient(getModifiers())
     * }
* * * @return {@code true} if and only if the underlying member was declared with variable arity. */ // spelling derived from java.lang.reflect.Executable, not MethodHandle.isVarargsCollector public default boolean isVarArgs() { // fields are never varargs: if (refKindIsField(getReferenceKind())) return false; // not in the public API: Modifier.VARARGS final int ACC_VARARGS = 0x00000080; // from JVMS 4.6 (Table 4.20) // Android-changed: Removed assert() due to http://b/30862573 // assert(ACC_VARARGS == Modifier.TRANSIENT); return Modifier.isTransient(getModifiers()); } /** * Returns the descriptive name of the given reference kind, * as defined in the table above. * The conventional prefix "REF_" is omitted. * @param referenceKind an integer code for a kind of reference used to access a class member * @return a mixed-case string such as {@code "getField"} * @exception IllegalArgumentException if the argument is not a valid * reference kind number */ public static String referenceKindToString(int referenceKind) { if (!refKindIsValid(referenceKind)) throw newIllegalArgumentException("invalid reference kind", referenceKind); return refKindName(referenceKind); } /** * Returns a string representation for a {@code MethodHandleInfo}, * given the four parts of its symbolic reference. * This is defined to be of the form {@code "RK C.N:MT"}, where {@code RK} is the * {@linkplain #referenceKindToString reference kind string} for {@code kind}, * {@code C} is the {@linkplain java.lang.Class#getName name} of {@code defc} * {@code N} is the {@code name}, and * {@code MT} is the {@code type}. * These four values may be obtained from the * {@linkplain #getReferenceKind reference kind}, * {@linkplain #getDeclaringClass declaring class}, * {@linkplain #getName member name}, * and {@linkplain #getMethodType method type} * of a {@code MethodHandleInfo} object. * * @implSpec * This produces a result equivalent to: *
{@code
     *     String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type)
     * }
* * @param kind the {@linkplain #getReferenceKind reference kind} part of the symbolic reference * @param defc the {@linkplain #getDeclaringClass declaring class} part of the symbolic reference * @param name the {@linkplain #getName member name} part of the symbolic reference * @param type the {@linkplain #getMethodType method type} part of the symbolic reference * @return a string of the form {@code "RK C.N:MT"} * @exception IllegalArgumentException if the first argument is not a valid * reference kind number * @exception NullPointerException if any reference argument is {@code null} */ public static String toString(int kind, Class defc, String name, MethodType type) { Objects.requireNonNull(name); Objects.requireNonNull(type); return String.format("%s %s.%s:%s", referenceKindToString(kind), defc.getName(), name, type); } // Android-changed: Inlined from MethodHandleNatives and changed to avoid references to // REF_NONE and REF_LIMITED static boolean refKindIsValid(int refKind) { return (refKind >= REF_getField && refKind <= REF_invokeInterface); } // Android-changed: Inlined from MethodHandleNatives. static boolean refKindIsField(int refKind) { return (refKind <= REF_putStatic); } // Android-changed: Inlined from MethodHandleNatives and replaced 'byte' argument with // 'int'. static String refKindName(int refKind) { switch (refKind) { case REF_getField: return "getField"; case REF_getStatic: return "getStatic"; case REF_putField: return "putField"; case REF_putStatic: return "putStatic"; case REF_invokeVirtual: return "invokeVirtual"; case REF_invokeStatic: return "invokeStatic"; case REF_invokeSpecial: return "invokeSpecial"; case REF_newInvokeSpecial: return "newInvokeSpecial"; case REF_invokeInterface: return "invokeInterface"; default: return "REF_???"; } } }