BaseDexClassLoader.java revision 0cfd9bcaa70317a8c400c39b25ad42ba05c7531a
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.Enumeration; 22 23/** 24 * Base class for common functionality between various dex-based 25 * {@link ClassLoader} implementations. 26 */ 27public class BaseDexClassLoader extends ClassLoader { 28 private final DexPathList pathList; 29 30 /** 31 * Constructs an instance. 32 * 33 * @param dexPath the list of jar/apk files containing classes and 34 * resources, delimited by {@code File.pathSeparator}, which 35 * defaults to {@code ":"} on Android 36 * @param optimizedDirectory directory where optimized dex files 37 * should be written; may be {@code null} 38 * @param libraryPath the list of directories containing native 39 * libraries, delimited by {@code File.pathSeparator}; may be 40 * {@code null} 41 * @param parent the parent class loader 42 */ 43 public BaseDexClassLoader(String dexPath, File optimizedDirectory, 44 String libraryPath, ClassLoader parent) { 45 super(parent); 46 this.pathList = new DexPathList(this, dexPath, libraryPath, optimizedDirectory); 47 } 48 49 @Override 50 protected Class<?> findClass(String name) throws ClassNotFoundException { 51 Class c = pathList.findClass(name); 52 if (c == null) { 53 throw new ClassNotFoundException("Didn't find class \"" + name + "\" on path: " + pathList); 54 } 55 return c; 56 } 57 58 @Override 59 protected URL findResource(String name) { 60 return pathList.findResource(name); 61 } 62 63 @Override 64 protected Enumeration<URL> findResources(String name) { 65 return pathList.findResources(name); 66 } 67 68 @Override 69 public String findLibrary(String name) { 70 return pathList.findLibrary(name); 71 } 72 73 /** 74 * Returns package information for the given package. 75 * Unfortunately, instances of this class don't really have this 76 * information, and as a non-secure {@code ClassLoader}, it isn't 77 * even required to, according to the spec. Yet, we want to 78 * provide it, in order to make all those hopeful callers of 79 * {@code myClass.getPackage().getName()} happy. Thus we construct 80 * a {@code Package} object the first time it is being requested 81 * and fill most of the fields with dummy values. The {@code 82 * Package} object is then put into the {@code ClassLoader}'s 83 * package cache, so we see the same one next time. We don't 84 * create {@code Package} objects for {@code null} arguments or 85 * for the default package. 86 * 87 * <p>There is a limited chance that we end up with multiple 88 * {@code Package} objects representing the same package: It can 89 * happen when when a package is scattered across different JAR 90 * files which were loaded by different {@code ClassLoader} 91 * instances. This is rather unlikely, and given that this whole 92 * thing is more or less a workaround, probably not worth the 93 * effort to address. 94 * 95 * @param name the name of the class 96 * @return the package information for the class, or {@code null} 97 * if there is no package information available for it 98 */ 99 @Override 100 protected synchronized Package getPackage(String name) { 101 if (name != null && !name.isEmpty()) { 102 Package pack = super.getPackage(name); 103 104 if (pack == null) { 105 pack = definePackage(name, "Unknown", "0.0", "Unknown", 106 "Unknown", "0.0", "Unknown", null); 107 } 108 109 return pack; 110 } 111 112 return null; 113 } 114 115 /** 116 * @hide 117 */ 118 public String getLdLibraryPath() { 119 StringBuilder result = new StringBuilder(); 120 for (File directory : pathList.getNativeLibraryDirectories()) { 121 if (result.length() > 0) { 122 result.append(':'); 123 } 124 result.append(directory); 125 } 126 return result.toString(); 127 } 128 129 @Override public String toString() { 130 return getClass().getName() + "[" + pathList + "]"; 131 } 132} 133