993 lines
34 KiB
Java
993 lines
34 KiB
Java
// ClassLoader.java - Define policies for loading Java classes.
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/* Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation
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This file is part of libgcj.
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This software is copyrighted work licensed under the terms of the
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Libgcj License. Please consult the file "LIBGCJ_LICENSE" for
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details. */
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package java.lang;
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import java.io.InputStream;
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import java.io.IOException;
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import java.net.URL;
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import java.security.AllPermission;
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import java.security.CodeSource;
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import java.security.Permission;
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import java.security.Permissions;
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import java.security.Policy;
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import java.security.ProtectionDomain;
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import java.util.*;
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/**
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* The ClassLoader is a way of customizing the way Java gets its classes
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* and loads them into memory. The verifier and other standard Java things
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* still run, but the ClassLoader is allowed great flexibility in determining
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* where to get the classfiles and when to load and resolve them. For that
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* matter, a custom ClassLoader can perform on-the-fly code generation or
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* modification!
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*
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* <p>Every classloader has a parent classloader that is consulted before
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* the 'child' classloader when classes or resources should be loaded.
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* This is done to make sure that classes can be loaded from an hierarchy of
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* multiple classloaders and classloaders do not accidentially redefine
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* already loaded classes by classloaders higher in the hierarchy.
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*
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* <p>The grandparent of all classloaders is the bootstrap classloader, which
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* loads all the standard system classes as implemented by GNU Classpath. The
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* other special classloader is the system classloader (also called
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* application classloader) that loads all classes from the CLASSPATH
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* (<code>java.class.path</code> system property). The system classloader
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* is responsible for finding the application classes from the classpath,
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* and delegates all requests for the standard library classes to its parent
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* the bootstrap classloader. Most programs will load all their classes
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* through the system classloaders.
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*
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* <p>The bootstrap classloader in GNU Classpath is implemented as a couple of
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* static (native) methods on the package private class
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* <code>java.lang.VMClassLoader</code>, the system classloader is an
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* instance of <code>gnu.java.lang.SystemClassLoader</code>
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* (which is a subclass of <code>java.net.URLClassLoader</code>).
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*
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* <p>Users of a <code>ClassLoader</code> will normally just use the methods
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* <ul>
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* <li> <code>loadClass()</code> to load a class.</li>
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* <li> <code>getResource()</code> or <code>getResourceAsStream()</code>
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* to access a resource.</li>
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* <li> <code>getResources()</code> to get an Enumeration of URLs to all
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* the resources provided by the classloader and its parents with the
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* same name.</li>
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* </ul>
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*
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* <p>Subclasses should implement the methods
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* <ul>
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* <li> <code>findClass()</code> which is called by <code>loadClass()</code>
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* when the parent classloader cannot provide a named class.</li>
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* <li> <code>findResource()</code> which is called by
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* <code>getResource()</code> when the parent classloader cannot provide
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* a named resource.</li>
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* <li> <code>findResources()</code> which is called by
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* <code>getResource()</code> to combine all the resources with the
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* same name from the classloader and its parents.</li>
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* <li> <code>findLibrary()</code> which is called by
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* <code>Runtime.loadLibrary()</code> when a class defined by the
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* classloader wants to load a native library.</li>
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* </ul>
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*
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* @author John Keiser
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* @author Mark Wielaard
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* @author Eric Blake
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* @author Kresten Krab Thorup
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* @see Class
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* @since 1.0
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* @status still missing 1.4 functionality
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*/
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public abstract class ClassLoader
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{
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/**
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* All classes loaded by this classloader. VM's may choose to implement
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* this cache natively; but it is here available for use if necessary. It
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* is not private in order to allow native code (and trusted subclasses)
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* access to this field.
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*/
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final Map loadedClasses = new HashMap();
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/**
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* The desired assertion status of classes loaded by this loader, if not
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* overridden by package or class instructions.
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*/
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// Package visible for use by Class.
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boolean defaultAssertionStatus = VMClassLoader.defaultAssertionStatus();
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/**
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* The command-line state of the package assertion status overrides. This
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* map is never modified, so it does not need to be synchronized.
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*/
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// Package visible for use by Class.
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static final Map systemPackageAssertionStatus
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= VMClassLoader.packageAssertionStatus();
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/**
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* The map of package assertion status overrides, or null if no package
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* overrides have been specified yet. The values of the map should be
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* Boolean.TRUE or Boolean.FALSE, and the unnamed package is represented
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* by the null key. This map must be synchronized on this instance.
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*/
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// Package visible for use by Class.
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Map packageAssertionStatus;
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/**
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* The command-line state of the class assertion status overrides. This
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* map is never modified, so it does not need to be synchronized.
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*/
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// Package visible for use by Class.
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static final Map systemClassAssertionStatus
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= VMClassLoader.classAssertionStatus();
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/**
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* The map of class assertion status overrides, or null if no class
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* overrides have been specified yet. The values of the map should be
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* Boolean.TRUE or Boolean.FALSE. This map must be synchronized on this
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* instance.
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*/
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// Package visible for use by Class.
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Map classAssertionStatus;
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/**
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* The classloader that is consulted before this classloader.
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* If null then the parent is the bootstrap classloader.
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*/
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private final ClassLoader parent;
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/**
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* All packages defined by this classloader. It is not private in order to
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* allow native code (and trusted subclasses) access to this field.
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*/
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private HashMap definedPackages = new HashMap();
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/**
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* Returns the parent of this classloader. If the parent of this
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* classloader is the bootstrap classloader then this method returns
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* <code>null</code>. A security check may be performed on
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* <code>RuntimePermission("getClassLoader")</code>.
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*
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* @throws SecurityException if the security check fails
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* @since 1.2
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*/
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public final ClassLoader getParent ()
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{
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// Check if we may return the parent classloader
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SecurityManager sm = System.getSecurityManager();
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if (sm != null)
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{
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/* FIXME: security, getClassContext() not implemented.
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Class c = VMSecurityManager.getClassContext()[1];
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ClassLoader cl = c.getClassLoader();
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if (cl != null && cl != this)
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sm.checkPermission(new RuntimePermission("getClassLoader"));
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*/
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}
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return parent;
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}
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/**
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* Returns the system classloader. The system classloader (also called
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* the application classloader) is the classloader that was used to
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* load the application classes on the classpath (given by the system
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* property <code>java.class.path</code>. This is set as the context
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* class loader for a thread. The system property
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* <code>java.system.class.loader</code>, if defined, is taken to be the
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* name of the class to use as the system class loader, which must have
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* a public constructor which takes a ClassLoader as a parent; otherwise this
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* uses gnu.java.lang.SystemClassLoader.
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*
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* <p>Note that this is different from the bootstrap classloader that
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* actually loads all the real "system" classes (the bootstrap classloader
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* is the parent of the returned system classloader).
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*
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* <p>A security check will be performed for
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* <code>RuntimePermission("getClassLoader")</code> if the calling class
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* is not a parent of the system class loader.
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*
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* @return the system class loader
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* @throws SecurityException if the security check fails
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* @throws IllegalStateException if this is called recursively
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* @throws Error if <code>java.system.class.loader</code> fails to load
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* @since 1.2
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*/
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public static ClassLoader getSystemClassLoader ()
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{
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return gnu.gcj.runtime.VMClassLoader.instance;
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}
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/**
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* Creates a <code>ClassLoader</code> with no parent.
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* @exception java.lang.SecurityException if not allowed
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*/
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protected ClassLoader()
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{
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this (null);
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}
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/**
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* Creates a <code>ClassLoader</code> with the given parent.
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* The parent may be <code>null</code>.
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* The only thing this
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* constructor does, is to call
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* <code>checkCreateClassLoader</code> on the current
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* security manager.
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* @exception java.lang.SecurityException if not allowed
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* @since 1.2
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*/
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protected ClassLoader(ClassLoader parent)
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{
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SecurityManager security = System.getSecurityManager ();
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if (security != null)
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security.checkCreateClassLoader ();
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this.parent = parent;
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}
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/**
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* Loads and link the class by the given name.
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* @param name the name of the class.
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* @return the class loaded.
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* @see ClassLoader#loadClass(String,boolean)
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* @exception java.lang.ClassNotFoundException
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*/
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public Class loadClass(String name)
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throws java.lang.ClassNotFoundException
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{
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return loadClass (name, false);
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}
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/**
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* Loads the class by the given name. The default implementation
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* will search for the class in the following order (similar to jdk 1.2)
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* <ul>
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* <li> First <code>findLoadedClass</code>.
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* <li> If parent is non-null, <code>parent.loadClass</code>;
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* otherwise <code>findSystemClass</code>.
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* <li> <code>findClass</code>.
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* </ul>
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* If <code>link</code> is true, <code>resolveClass</code> is then
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* called. <p> Normally, this need not be overridden; override
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* <code>findClass</code> instead.
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* @param name the name of the class.
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* @param link if the class should be linked.
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* @return the class loaded.
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* @exception java.lang.ClassNotFoundException
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* @deprecated
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*/
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protected Class loadClass(String name, boolean link)
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throws java.lang.ClassNotFoundException
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{
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Class c = findLoadedClass (name);
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if (c == null)
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{
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try
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{
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ClassLoader cl = parent;
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if (parent == null)
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cl = gnu.gcj.runtime.VMClassLoader.instance;
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if (cl != this)
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c = cl.loadClass (name, link);
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}
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catch (ClassNotFoundException ex)
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{
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/* ignore, we'll try findClass */;
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}
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}
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if (c == null)
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c = findClass (name);
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if (c == null)
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throw new ClassNotFoundException (name);
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if (link)
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resolveClass (c);
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return c;
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}
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/**
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* Called for every class name that is needed but has not yet been
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* defined by this classloader or one of its parents. It is called by
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* <code>loadClass()</code> after both <code>findLoadedClass()</code> and
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* <code>parent.loadClass()</code> couldn't provide the requested class.
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*
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* <p>The default implementation throws a
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* <code>ClassNotFoundException</code>. Subclasses should override this
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* method. An implementation of this method in a subclass should get the
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* class bytes of the class (if it can find them), if the package of the
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* requested class doesn't exist it should define the package and finally
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* it should call define the actual class. It does not have to resolve the
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* class. It should look something like the following:<br>
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*
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* <pre>
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* // Get the bytes that describe the requested class
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* byte[] classBytes = classLoaderSpecificWayToFindClassBytes(name);
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* // Get the package name
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* int lastDot = name.lastIndexOf('.');
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* if (lastDot != -1)
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* {
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* String packageName = name.substring(0, lastDot);
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* // Look if the package already exists
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* if (getPackage(pkg) == null)
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* {
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* // define the package
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* definePackage(packageName, ...);
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* }
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* }
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* // Define and return the class
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* return defineClass(name, classBytes, 0, classBytes.length);
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* </pre>
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*
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* <p><code>loadClass()</code> makes sure that the <code>Class</code>
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* returned by <code>findClass()</code> will later be returned by
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* <code>findLoadedClass()</code> when the same class name is requested.
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*
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* @param name class name to find (including the package name)
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* @return the requested Class
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* @throws ClassNotFoundException when the class can not be found
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* @since 1.2
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*/
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protected Class findClass (String name)
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throws ClassNotFoundException
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{
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throw new ClassNotFoundException (name);
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}
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// Protection Domain definitions
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// FIXME: should there be a special protection domain used for native code?
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// The permission required to check what a classes protection domain is.
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static final Permission protectionDomainPermission
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= new RuntimePermission("getProtectionDomain");
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// The protection domain returned if we cannot determine it.
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static ProtectionDomain unknownProtectionDomain;
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// Protection domain to use when a class is defined without one specified.
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static ProtectionDomain defaultProtectionDomain;
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static
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{
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Permissions permissions = new Permissions();
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permissions.add(new AllPermission());
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unknownProtectionDomain = new ProtectionDomain(null, permissions);
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CodeSource cs = new CodeSource(null, null);
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defaultProtectionDomain =
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new ProtectionDomain(cs, Policy.getPolicy().getPermissions(cs));
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}
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/**
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* Defines a class, given the class-data. According to the JVM, this
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* method should not be used; instead use the variant of this method
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* in which the name of the class being defined is specified
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* explicitly.
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* <P>
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* If the name of the class, as specified (implicitly) in the class
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* data, denotes a class which has already been loaded by this class
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* loader, an instance of
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* <code>java.lang.ClassNotFoundException</code> will be thrown.
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*
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* @param data bytes in class file format.
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* @param off offset to start interpreting data.
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* @param len length of data in class file.
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* @return the class defined.
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* @exception java.lang.ClassNotFoundException
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* @exception java.lang.LinkageError
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* @see ClassLoader#defineClass(String,byte[],int,int) */
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protected final Class defineClass(byte[] data, int off, int len)
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throws ClassFormatError
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{
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return defineClass (null, data, off, len, defaultProtectionDomain);
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}
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/**
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* Helper to define a class using a string of bytes without a
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* ProtectionDomain. Subclasses should call this method from their
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* <code>findClass()</code> implementation. The name should use '.'
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* separators, and discard the trailing ".class". The default protection
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* domain has the permissions of
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* <code>Policy.getPolicy().getPermissions(new CodeSource(null, null))<code>.
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*
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* @param name the name to give the class, or null if unknown
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* @param data the data representing the classfile, in classfile format
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* @param offset the offset into the data where the classfile starts
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* @param len the length of the classfile data in the array
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* @return the class that was defined
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* @throws ClassFormatError if data is not in proper classfile format
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* @throws IndexOutOfBoundsException if offset or len is negative, or
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* offset + len exceeds data
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* @throws SecurityException if name starts with "java."
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* @since 1.1
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*/
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protected final Class defineClass(String name, byte[] data, int off, int len)
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throws ClassFormatError
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{
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return defineClass (name, data, off, len, defaultProtectionDomain);
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}
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/**
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* Defines a class, given the class-data. This is preferable
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* over <code>defineClass(byte[],off,len)</code> since it is more
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* secure. If the expected name does not match that of the class
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* file, <code>ClassNotFoundException</code> is thrown. If
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* <code>name</code> denotes the name of an already loaded class, a
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* <code>LinkageError</code> is thrown.
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* <p>
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*
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* FIXME: How do we assure that the class-file data is not being
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* modified, simultaneously with the class loader running!? If this
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* was done in some very clever way, it might break security.
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* Right now I am thinking that defineclass should make sure never to
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* read an element of this array more than once, and that that would
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* assure the ``immutable'' appearance. It is still to be determined
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* if this is in fact how defineClass operates.
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*
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* @param name the expected name.
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* @param data bytes in class file format.
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* @param off offset to start interpreting data.
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* @param len length of data in class file.
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* @param protectionDomain security protection domain for the class.
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* @return the class defined.
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* @exception java.lang.ClassNotFoundException
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* @exception java.lang.LinkageError
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*/
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protected final synchronized Class defineClass(String name,
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byte[] data,
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int off,
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int len,
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ProtectionDomain protectionDomain)
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throws ClassFormatError
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{
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if (data==null || data.length < off+len || off<0 || len<0)
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throw new ClassFormatError ("arguments to defineClass "
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+ "are meaningless");
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// as per 5.3.5.1
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if (name != null && findLoadedClass (name) != null)
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throw new java.lang.LinkageError ("class "
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+ name
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+ " already loaded");
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if (protectionDomain == null)
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protectionDomain = defaultProtectionDomain;
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try
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{
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Class retval = defineClass0 (name, data, off, len, protectionDomain);
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loadedClasses.put(retval.getName(), retval);
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return retval;
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}
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catch (LinkageError x)
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{
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throw x; // rethrow
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}
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catch (java.lang.VirtualMachineError x)
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{
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throw x; // rethrow
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}
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catch (java.lang.Throwable x)
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{
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// This should never happen, or we are beyond spec.
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throw new InternalError ("Unexpected exception "
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+ "while defining class "
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+ name + ": "
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+ x.toString ());
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}
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}
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/** This is the entry point of defineClass into the native code */
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private native Class defineClass0 (String name,
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byte[] data,
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int off,
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int len,
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ProtectionDomain protectionDomain)
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throws ClassFormatError;
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/**
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* Link the given class. This will bring the class to a state where
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* the class initializer can be run. Linking involves the following
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* steps:
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* <UL>
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* <LI> Prepare (allocate and internalize) the constant strings that
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* are used in this class.
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* <LI> Allocate storage for static fields, and define the layout
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* of instance fields.
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* <LI> Perform static initialization of ``static final'' int,
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* long, float, double and String fields for which there is a
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* compile-time constant initializer.
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* <LI> Create the internal representation of the ``vtable''.
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* </UL>
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* For <code>gcj</code>-compiled classes, only the first step is
|
|
* performed. The compiler will have done the rest already.
|
|
* <P>
|
|
* This is called by the system automatically,
|
|
* as part of class initialization; there is no reason to ever call
|
|
* this method directly.
|
|
* <P>
|
|
* For historical reasons, this method has a name which is easily
|
|
* misunderstood. Java classes are never ``resolved''. Classes are
|
|
* linked; whereas method and field references are resolved.
|
|
*
|
|
* @param clazz the class to link.
|
|
* @exception java.lang.LinkageError
|
|
*/
|
|
protected final void resolveClass(Class clazz)
|
|
{
|
|
resolveClass0(clazz);
|
|
}
|
|
|
|
static void resolveClass0(Class clazz)
|
|
{
|
|
synchronized (clazz)
|
|
{
|
|
try
|
|
{
|
|
linkClass0 (clazz);
|
|
}
|
|
catch (Throwable x)
|
|
{
|
|
markClassErrorState0 (clazz);
|
|
|
|
if (x instanceof Error)
|
|
throw (Error)x;
|
|
else
|
|
{
|
|
InternalError e
|
|
= new InternalError ("unexpected exception during linking: "
|
|
+ clazz.getName());
|
|
e.initCause (x);
|
|
throw e;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/** Internal method. Calls _Jv_PrepareClass and
|
|
* _Jv_PrepareCompiledClass. This is only called from resolveClass. */
|
|
private static native void linkClass0(Class clazz);
|
|
|
|
/** Internal method. Marks the given clazz to be in an erroneous
|
|
* state, and calls notifyAll() on the class object. This should only
|
|
* be called when the caller has the lock on the class object. */
|
|
private static native void markClassErrorState0(Class clazz);
|
|
|
|
/**
|
|
* Defines a new package and creates a Package object.
|
|
* The package should be defined before any class in the package is
|
|
* defined with <code>defineClass()</code>. The package should not yet
|
|
* be defined before in this classloader or in one of its parents (which
|
|
* means that <code>getPackage()</code> should return <code>null</code>).
|
|
* All parameters except the <code>name</code> of the package may be
|
|
* <code>null</code>.
|
|
* <p>
|
|
* Subclasses should call this method from their <code>findClass()</code>
|
|
* implementation before calling <code>defineClass()</code> on a Class
|
|
* in a not yet defined Package (which can be checked by calling
|
|
* <code>getPackage()</code>).
|
|
*
|
|
* @param name The name of the Package
|
|
* @param specTitle The name of the specification
|
|
* @param specVendor The name of the specification designer
|
|
* @param specVersion The version of this specification
|
|
* @param implTitle The name of the implementation
|
|
* @param implVendor The vendor that wrote this implementation
|
|
* @param implVersion The version of this implementation
|
|
* @param sealed If sealed the origin of the package classes
|
|
* @return the Package object for the specified package
|
|
*
|
|
* @exception IllegalArgumentException if the package name is null or if
|
|
* it was already defined by this classloader or one of its parents.
|
|
*
|
|
* @see Package
|
|
* @since 1.2
|
|
*/
|
|
protected Package definePackage(String name,
|
|
String specTitle, String specVendor,
|
|
String specVersion, String implTitle,
|
|
String implVendor, String implVersion,
|
|
URL sealed)
|
|
{
|
|
if (getPackage(name) != null)
|
|
throw new IllegalArgumentException("Package " + name
|
|
+ " already defined");
|
|
Package p = new Package(name,
|
|
specTitle, specVendor, specVersion,
|
|
implTitle, implVendor, implVersion,
|
|
sealed);
|
|
synchronized (definedPackages)
|
|
{
|
|
definedPackages.put(name, p);
|
|
}
|
|
return p;
|
|
}
|
|
|
|
/**
|
|
* Returns the Package object for the requested package name. It returns
|
|
* null when the package is not defined by this classloader or one of its
|
|
* parents.
|
|
*
|
|
* @param name the package name to find
|
|
* @return the package, if defined
|
|
* @since 1.2
|
|
*/
|
|
protected Package getPackage(String name)
|
|
{
|
|
Package p;
|
|
if (parent == null)
|
|
// XXX - Should we use the bootstrap classloader?
|
|
p = null;
|
|
else
|
|
p = parent.getPackage(name);
|
|
|
|
if (p == null)
|
|
{
|
|
synchronized (definedPackages)
|
|
{
|
|
p = (Package) definedPackages.get(name);
|
|
}
|
|
}
|
|
|
|
return p;
|
|
}
|
|
|
|
/**
|
|
* Returns all Package objects defined by this classloader and its parents.
|
|
*
|
|
* @return an array of all defined packages
|
|
* @since 1.2
|
|
*/
|
|
protected Package[] getPackages()
|
|
{
|
|
Package[] allPackages;
|
|
|
|
// Get all our packages.
|
|
Package[] packages;
|
|
synchronized(definedPackages)
|
|
{
|
|
packages = new Package[definedPackages.size()];
|
|
definedPackages.values().toArray(packages);
|
|
}
|
|
|
|
// If we have a parent get all packages defined by our parents.
|
|
if (parent != null)
|
|
{
|
|
Package[] parentPackages = parent.getPackages();
|
|
allPackages = new Package[parentPackages.length + packages.length];
|
|
System.arraycopy(parentPackages, 0, allPackages, 0,
|
|
parentPackages.length);
|
|
System.arraycopy(packages, 0, allPackages, parentPackages.length,
|
|
packages.length);
|
|
}
|
|
else
|
|
// XXX - Should we use the bootstrap classloader?
|
|
allPackages = packages;
|
|
|
|
return allPackages;
|
|
}
|
|
|
|
/**
|
|
* Called by <code>Runtime.loadLibrary()</code> to get an absolute path
|
|
* to a (system specific) library that was requested by a class loaded
|
|
* by this classloader. The default implementation returns
|
|
* <code>null</code>. It should be implemented by subclasses when they
|
|
* have a way to find the absolute path to a library. If this method
|
|
* returns null the library is searched for in the default locations
|
|
* (the directories listed in the <code>java.library.path</code> system
|
|
* property).
|
|
*
|
|
* @param name the (system specific) name of the requested library
|
|
* @return the full pathname to the requested library, or null
|
|
* @see Runtime#loadLibrary()
|
|
* @since 1.2
|
|
*/
|
|
protected String findLibrary(String name)
|
|
{
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Returns a class found in a system-specific way, typically
|
|
* via the <code>java.class.path</code> system property. Loads the
|
|
* class if necessary.
|
|
*
|
|
* @param name the class to resolve.
|
|
* @return the class loaded.
|
|
* @exception java.lang.LinkageError
|
|
* @exception java.lang.ClassNotFoundException
|
|
*/
|
|
protected final Class findSystemClass(String name)
|
|
throws java.lang.ClassNotFoundException
|
|
{
|
|
return gnu.gcj.runtime.VMClassLoader.instance.loadClass (name);
|
|
}
|
|
|
|
/**
|
|
* Helper to set the signers of a class. This should be called after
|
|
* defining the class.
|
|
*
|
|
* @param c the Class to set signers of
|
|
* @param signers the signers to set
|
|
* @since 1.1
|
|
*/
|
|
protected final void setSigners(Class c, Object[] signers)
|
|
{
|
|
/*
|
|
* Does currently nothing. FIXME.
|
|
*/
|
|
}
|
|
|
|
/**
|
|
* If a class named <code>name</code> was previously loaded using
|
|
* this <code>ClassLoader</code>, then it is returned. Otherwise
|
|
* it returns <code>null</code>. (Unlike the JDK this is native,
|
|
* since we implement the class table internally.)
|
|
* @param name class to find.
|
|
* @return the class loaded, or null.
|
|
*/
|
|
protected final synchronized Class findLoadedClass(String name)
|
|
{
|
|
return (Class) loadedClasses.get(name);
|
|
}
|
|
|
|
/**
|
|
* Get a resource using the system classloader.
|
|
*
|
|
* @param name the name of the resource relative to the system classloader
|
|
* @return an input stream for the resource, or null
|
|
* @since 1.1
|
|
*/
|
|
public static InputStream getSystemResourceAsStream(String name) {
|
|
return getSystemClassLoader().getResourceAsStream (name);
|
|
}
|
|
|
|
/**
|
|
* Get the URL to a resource using the system classloader.
|
|
*
|
|
* @param name the name of the resource relative to the system classloader
|
|
* @return the URL to the resource
|
|
* @since 1.1
|
|
*/
|
|
public static URL getSystemResource(String name) {
|
|
return getSystemClassLoader().getResource (name);
|
|
}
|
|
|
|
/**
|
|
* Get an Enumeration of URLs to resources with a given name using the
|
|
* the system classloader. The enumeration firsts lists the resources with
|
|
* the given name that can be found by the bootstrap classloader followed
|
|
* by the resources with the given name that can be found on the classpath.
|
|
*
|
|
* @param name the name of the resource relative to the system classloader
|
|
* @return an Enumeration of URLs to the resources
|
|
* @throws IOException if I/O errors occur in the process
|
|
* @since 1.2
|
|
*/
|
|
public static Enumeration getSystemResources(String name) throws IOException
|
|
{
|
|
return getSystemClassLoader().getResources(name);
|
|
}
|
|
|
|
/**
|
|
* Return an InputStream representing the resource name.
|
|
* This is essentially like
|
|
* <code>getResource(name).openStream()</code>, except
|
|
* it masks out any IOException and returns null on failure.
|
|
* @param name resource to load
|
|
* @return an InputStream, or null
|
|
* @see java.lang.ClassLoader#getResource(String)
|
|
* @see java.io.InputStream
|
|
*/
|
|
public InputStream getResourceAsStream(String name)
|
|
{
|
|
try
|
|
{
|
|
URL res = getResource (name);
|
|
if (res == null)
|
|
return null;
|
|
return res.openStream ();
|
|
}
|
|
catch (java.io.IOException x)
|
|
{
|
|
return null;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* Return an java.io.URL representing the resouce <code>name</code>.
|
|
* The default implementation just returns <code>null</code>.
|
|
* @param name resource to load
|
|
* @return a URL, or null if there is no such resource.
|
|
* @see java.lang.ClassLoader#getResourceAsBytes(String)
|
|
* @see java.lang.ClassLoader#getResourceAsStream(String)
|
|
* @see java.io.URL
|
|
*/
|
|
public URL getResource (String name)
|
|
{
|
|
// The rules say search the parent class if non-null,
|
|
// otherwise search the built-in class loader (assumed to be
|
|
// the system ClassLoader). If not found, call
|
|
// findResource().
|
|
URL result = null;
|
|
|
|
ClassLoader delegate = parent;
|
|
|
|
if (delegate == null)
|
|
delegate = getSystemClassLoader ();
|
|
|
|
// Protect ourselves from looping.
|
|
if (this != delegate)
|
|
result = delegate.getResource (name);
|
|
|
|
if (result != null)
|
|
return result;
|
|
else
|
|
return findResource (name);
|
|
}
|
|
|
|
/**
|
|
* Called whenever a resource is needed that could not be provided by
|
|
* one of the parents of this classloader. It is called by
|
|
* <code>getResource()</code> after <code>parent.getResource()</code>
|
|
* couldn't provide the requested resource.
|
|
*
|
|
* <p>The default implementation always returns null. Subclasses should
|
|
* override this method when they can provide a way to return a URL
|
|
* to a named resource.
|
|
*
|
|
* @param name the name of the resource to be found
|
|
* @return a URL to the named resource or null when not found
|
|
* @since 1.2
|
|
*/
|
|
protected URL findResource (String name)
|
|
{
|
|
// Default to returning null. Derived classes implement this.
|
|
return null;
|
|
}
|
|
|
|
/**
|
|
* Returns an Enumeration of all resources with a given name that can
|
|
* be found by this classloader and its parents. Certain classloaders
|
|
* (such as the URLClassLoader when given multiple jar files) can have
|
|
* multiple resources with the same name that come from multiple locations.
|
|
* It can also occur that a parent classloader offers a resource with a
|
|
* certain name and the child classloader also offers a resource with that
|
|
* same name. <code>getResource() only offers the first resource (of the
|
|
* parent) with a given name. This method lists all resources with the
|
|
* same name. The name should use '/' as path separators.
|
|
*
|
|
* <p>The Enumeration is created by first calling <code>getResources()</code>
|
|
* on the parent classloader and then calling <code>findResources()</code>
|
|
* on this classloader.
|
|
*
|
|
* @param name the resource name
|
|
* @return an enumaration of all resources found
|
|
* @throws IOException if I/O errors occur in the process
|
|
* @since 1.2
|
|
*/
|
|
public final Enumeration getResources(String name) throws IOException
|
|
{
|
|
// The rules say search the parent class if non-null,
|
|
// otherwise search the built-in class loader (assumed to be
|
|
// the system ClassLoader). If not found, call
|
|
// findResource().
|
|
Enumeration result = null;
|
|
|
|
ClassLoader delegate = parent;
|
|
|
|
if (delegate == null)
|
|
delegate = getSystemClassLoader ();
|
|
|
|
// Protect ourselves from looping.
|
|
if (this != delegate)
|
|
result = delegate.getResources (name);
|
|
|
|
if (result != null)
|
|
return result;
|
|
else
|
|
return findResources (name);
|
|
}
|
|
|
|
/**
|
|
* Called whenever all locations of a named resource are needed.
|
|
* It is called by <code>getResources()</code> after it has called
|
|
* <code>parent.getResources()</code>. The results are combined by
|
|
* the <code>getResources()</code> method.
|
|
*
|
|
* <p>The default implementation always returns an empty Enumeration.
|
|
* Subclasses should override it when they can provide an Enumeration of
|
|
* URLs (possibly just one element) to the named resource.
|
|
* The first URL of the Enumeration should be the same as the one
|
|
* returned by <code>findResource</code>.
|
|
*
|
|
* @param name the name of the resource to be found
|
|
* @return a possibly empty Enumeration of URLs to the named resource
|
|
* @throws IOException if I/O errors occur in the process
|
|
* @since 1.2
|
|
*/
|
|
protected Enumeration findResources(String name) throws IOException
|
|
{
|
|
return Collections.enumeration(Collections.EMPTY_LIST);
|
|
}
|
|
|
|
/**
|
|
* Set the default assertion status for classes loaded by this classloader,
|
|
* used unless overridden by a package or class request.
|
|
*
|
|
* @param enabled true to set the default to enabled
|
|
* @see #setClassAssertionStatus(String, boolean)
|
|
* @see #setPackageAssertionStatus(String, boolean)
|
|
* @see #clearAssertionStatus()
|
|
* @since 1.4
|
|
*/
|
|
public void setDefaultAssertionStatus(boolean enabled)
|
|
{
|
|
defaultAssertionStatus = enabled;
|
|
}
|
|
|
|
/**
|
|
* Set the default assertion status for packages, used unless overridden
|
|
* by a class request. This default also covers subpackages, unless they
|
|
* are also specified. The unnamed package should use null for the name.
|
|
*
|
|
* @param name the package (and subpackages) to affect
|
|
* @param enabled true to set the default to enabled
|
|
* @see #setDefaultAssertionStatus(String, boolean)
|
|
* @see #setClassAssertionStatus(String, boolean)
|
|
* @see #clearAssertionStatus()
|
|
* @since 1.4
|
|
*/
|
|
public synchronized void setPackageAssertionStatus(String name,
|
|
boolean enabled)
|
|
{
|
|
if (packageAssertionStatus == null)
|
|
packageAssertionStatus
|
|
= new HashMap(systemPackageAssertionStatus);
|
|
packageAssertionStatus.put(name, Boolean.valueOf(enabled));
|
|
}
|
|
|
|
/**
|
|
* Set the default assertion status for a class. This only affects the
|
|
* status of top-level classes, any other string is harmless.
|
|
*
|
|
* @param name the class to affect
|
|
* @param enabled true to set the default to enabled
|
|
* @throws NullPointerException if name is null
|
|
* @see #setDefaultAssertionStatus(String, boolean)
|
|
* @see #setPackageAssertionStatus(String, boolean)
|
|
* @see #clearAssertionStatus()
|
|
* @since 1.4
|
|
*/
|
|
public synchronized void setClassAssertionStatus(String name,
|
|
boolean enabled)
|
|
{
|
|
if (classAssertionStatus == null)
|
|
classAssertionStatus = new HashMap(systemClassAssertionStatus);
|
|
// The toString() hack catches null, as required.
|
|
classAssertionStatus.put(name.toString(), Boolean.valueOf(enabled));
|
|
}
|
|
|
|
/**
|
|
* Resets the default assertion status of this classloader, its packages
|
|
* and classes, all to false. This allows overriding defaults inherited
|
|
* from the command line.
|
|
*
|
|
* @see #setDefaultAssertionStatus(boolean)
|
|
* @see #setClassAssertionStatus(String, boolean)
|
|
* @see #setPackageAssertionStatus(String, boolean)
|
|
* @since 1.4
|
|
*/
|
|
public synchronized void clearAssertionStatus()
|
|
{
|
|
defaultAssertionStatus = false;
|
|
packageAssertionStatus = new HashMap();
|
|
classAssertionStatus = new HashMap();
|
|
}
|
|
}
|