1/*
2 * Copyright (C) 2011 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package dalvik.system;
18
19import java.io.File;
20import java.net.URL;
21import java.util.ArrayList;
22import java.util.Enumeration;
23import java.util.List;
24
25/**
26 * Base class for common functionality between various dex-based
27 * {@link ClassLoader} implementations.
28 */
29public class BaseDexClassLoader extends ClassLoader {
30    private final DexPathList pathList;
31
32    /**
33     * Constructs an instance.
34     *
35     * @param dexPath the list of jar/apk files containing classes and
36     * resources, delimited by {@code File.pathSeparator}, which
37     * defaults to {@code ":"} on Android
38     * @param optimizedDirectory directory where optimized dex files
39     * should be written; may be {@code null}
40     * @param librarySearchPath the list of directories containing native
41     * libraries, delimited by {@code File.pathSeparator}; may be
42     * {@code null}
43     * @param parent the parent class loader
44     */
45    public BaseDexClassLoader(String dexPath, File optimizedDirectory,
46            String librarySearchPath, ClassLoader parent) {
47        super(parent);
48        this.pathList = new DexPathList(this, dexPath, librarySearchPath, optimizedDirectory);
49    }
50
51    @Override
52    protected Class<?> findClass(String name) throws ClassNotFoundException {
53        List<Throwable> suppressedExceptions = new ArrayList<Throwable>();
54        Class c = pathList.findClass(name, suppressedExceptions);
55        if (c == null) {
56            ClassNotFoundException cnfe = new ClassNotFoundException("Didn't find class \"" + name + "\" on path: " + pathList);
57            for (Throwable t : suppressedExceptions) {
58                cnfe.addSuppressed(t);
59            }
60            throw cnfe;
61        }
62        return c;
63    }
64
65    /**
66     * @hide
67     */
68    public void addDexPath(String dexPath) {
69        pathList.addDexPath(dexPath, null /*optimizedDirectory*/);
70    }
71
72    @Override
73    protected URL findResource(String name) {
74        return pathList.findResource(name);
75    }
76
77    @Override
78    protected Enumeration<URL> findResources(String name) {
79        return pathList.findResources(name);
80    }
81
82    @Override
83    public String findLibrary(String name) {
84        return pathList.findLibrary(name);
85    }
86
87    /**
88     * Returns package information for the given package.
89     * Unfortunately, instances of this class don't really have this
90     * information, and as a non-secure {@code ClassLoader}, it isn't
91     * even required to, according to the spec. Yet, we want to
92     * provide it, in order to make all those hopeful callers of
93     * {@code myClass.getPackage().getName()} happy. Thus we construct
94     * a {@code Package} object the first time it is being requested
95     * and fill most of the fields with dummy values. The {@code
96     * Package} object is then put into the {@code ClassLoader}'s
97     * package cache, so we see the same one next time. We don't
98     * create {@code Package} objects for {@code null} arguments or
99     * for the default package.
100     *
101     * <p>There is a limited chance that we end up with multiple
102     * {@code Package} objects representing the same package: It can
103     * happen when when a package is scattered across different JAR
104     * files which were loaded by different {@code ClassLoader}
105     * instances. This is rather unlikely, and given that this whole
106     * thing is more or less a workaround, probably not worth the
107     * effort to address.
108     *
109     * @param name the name of the class
110     * @return the package information for the class, or {@code null}
111     * if there is no package information available for it
112     */
113    @Override
114    protected synchronized Package getPackage(String name) {
115        if (name != null && !name.isEmpty()) {
116            Package pack = super.getPackage(name);
117
118            if (pack == null) {
119                pack = definePackage(name, "Unknown", "0.0", "Unknown",
120                        "Unknown", "0.0", "Unknown", null);
121            }
122
123            return pack;
124        }
125
126        return null;
127    }
128
129    /**
130     * @hide
131     */
132    public String getLdLibraryPath() {
133        StringBuilder result = new StringBuilder();
134        for (File directory : pathList.getNativeLibraryDirectories()) {
135            if (result.length() > 0) {
136                result.append(':');
137            }
138            result.append(directory);
139        }
140
141        return result.toString();
142    }
143
144    @Override public String toString() {
145        return getClass().getName() + "[" + pathList + "]";
146    }
147}
148