mirror of git://gcc.gnu.org/git/gcc.git
581 lines
18 KiB
Java
581 lines
18 KiB
Java
// ClassLoader.java - Define policies for loading Java classes.
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/* Copyright (C) 1998, 1999, 2000, 2001 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.net.URLConnection;
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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.Enumeration;
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import java.util.HashMap;
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import java.util.Stack;
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/**
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* The class <code>ClassLoader</code> is intended to be subclassed by
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* applications in order to describe new ways of loading classes,
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* such as over the network.
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*
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* @author Kresten Krab Thorup
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*/
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public abstract class ClassLoader
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{
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private ClassLoader parent;
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private HashMap definedPackages = new HashMap();
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public final ClassLoader getParent ()
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{
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/* FIXME: security */
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return parent;
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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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if (parent != null)
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return parent.loadClass (name, link);
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else
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c = gnu.gcj.runtime.VMClassLoader.instance.findClass (name);
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} catch (ClassNotFoundException ex) {
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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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/** Find a class. This should be overridden by subclasses; the
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* default implementation throws ClassNotFoundException.
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*
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* @param name Name of the class to find.
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* @return The class found.
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* @exception java.lang.ClassNotFoundException
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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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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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// Since we're calling into native code here,
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// we better make sure that any generated
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// exception is to spec!
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return defineClass0 (name, data, off, len, protectionDomain);
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} catch (LinkageError x) {
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throw x; // rethrow
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} catch (java.lang.VirtualMachineError x) {
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throw x; // rethrow
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} catch (java.lang.Throwable x) {
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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
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* performed. The compiler will have done the rest already.
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* <P>
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* This is called by the system automatically,
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* as part of class initialization; there is no reason to ever call
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* this method directly.
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* <P>
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* For historical reasons, this method has a name which is easily
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* misunderstood. Java classes are never ``resolved''. Classes are
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* linked; whereas method and field references are resolved.
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*
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* @param clazz the class to link.
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* @exception java.lang.LinkageError
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*/
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protected final void resolveClass(Class clazz)
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{
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resolveClass0(clazz);
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}
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static void resolveClass0(Class clazz)
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{
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synchronized (clazz)
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{
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try {
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linkClass0 (clazz);
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} catch (Throwable x) {
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markClassErrorState0 (clazz);
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if (x instanceof Error)
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throw (Error)x;
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else
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throw new java.lang.InternalError
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("unexpected exception during linking: " + x);
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}
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}
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}
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/** Internal method. Calls _Jv_PrepareClass and
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* _Jv_PrepareCompiledClass. This is only called from resolveClass. */
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private static native void linkClass0(Class clazz);
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/** Internal method. Marks the given clazz to be in an erroneous
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* state, and calls notifyAll() on the class object. This should only
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* be called when the caller has the lock on the class object. */
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private static native void markClassErrorState0(Class clazz);
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/**
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* Defines a new package and creates a Package object.
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* The package should be defined before any class in the package is
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* defined with <code>defineClass()</code>. The package should not yet
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* be defined before in this classloader or in one of its parents (which
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* means that <code>getPackage()</code> should return <code>null</code>).
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* All parameters except the <code>name</code> of the package may be
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* <code>null</code>.
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* <p>
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* Subclasses should call this method from their <code>findClass()</code>
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* implementation before calling <code>defineClass()</code> on a Class
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* in a not yet defined Package (which can be checked by calling
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* <code>getPackage()</code>).
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*
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* @param name The name of the Package
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* @param specTitle The name of the specification
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* @param specVendor The name of the specification designer
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* @param specVersion The version of this specification
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* @param implTitle The name of the implementation
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* @param implVendor The vendor that wrote this implementation
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* @param implVersion The version of this implementation
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* @param sealed If sealed the origin of the package classes
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* @return the Package object for the specified package
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*
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* @exception IllegalArgumentException if the package name is null or if
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* it was already defined by this classloader or one of its parents.
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*
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* @see Package
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* @since 1.2
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*/
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protected Package definePackage(String name,
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String specTitle, String specVendor,
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String specVersion, String implTitle,
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String implVendor, String implVersion,
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URL sealed)
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{
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if (getPackage(name) != null)
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throw new IllegalArgumentException("Package " + name
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+ " already defined");
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Package p = new Package(name,
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specTitle, specVendor, specVersion,
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implTitle, implVendor, implVersion,
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sealed);
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synchronized (definedPackages)
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{
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definedPackages.put(name, p);
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}
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return p;
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}
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/**
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* Returns the Package object for the requested package name. It returns
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* null when the package is not defined by this classloader or one of its
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* parents.
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*
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* @since 1.2
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*/
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protected Package getPackage(String name)
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{
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Package p;
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if (parent == null)
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// XXX - Should we use the bootstrap classloader?
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p = null;
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else
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p = parent.getPackage(name);
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if (p == null)
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{
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synchronized (definedPackages)
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{
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p = (Package) definedPackages.get(name);
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}
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}
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return p;
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}
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/**
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* Returns all Package objects defined by this classloader and its parents.
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*
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* @since 1.2
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*/
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protected Package[] getPackages()
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{
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Package[] allPackages;
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// Get all our packages.
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Package[] packages;
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synchronized(definedPackages)
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{
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packages = new Package[definedPackages.size()];
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definedPackages.values().toArray(packages);
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}
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// If we have a parent get all packages defined by our parents.
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if (parent != null)
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{
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Package[] parentPackages = parent.getPackages();
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allPackages = new Package[parentPackages.length + packages.length];
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System.arraycopy(parentPackages, 0, allPackages, 0,
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parentPackages.length);
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System.arraycopy(packages, 0, allPackages, parentPackages.length,
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packages.length);
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}
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else
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// XXX - Should we use the bootstrap classloader?
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allPackages = packages;
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return allPackages;
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}
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/**
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* Returns a class found in a system-specific way, typically
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* via the <code>java.class.path</code> system property. Loads the
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* class if necessary.
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*
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* @param name the class to resolve.
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* @return the class loaded.
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* @exception java.lang.LinkageError
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* @exception java.lang.ClassNotFoundException
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*/
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protected final Class findSystemClass(String name)
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throws java.lang.ClassNotFoundException
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{
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return gnu.gcj.runtime.VMClassLoader.instance.loadClass (name);
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}
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/*
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* Does currently nothing. FIXME.
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*/
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protected final void setSigners(Class claz, Object[] signers) {
|
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/* claz.setSigners (signers); */
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}
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|
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/**
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* If a class named <code>name</code> was previously loaded using
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* this <code>ClassLoader</code>, then it is returned. Otherwise
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* it returns <code>null</code>. (Unlike the JDK this is native,
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* since we implement the class table internally.)
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* @param name class to find.
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* @return the class loaded, or null.
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*/
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protected final native Class findLoadedClass(String name);
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public static InputStream getSystemResourceAsStream(String name) {
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return getSystemClassLoader().getResourceAsStream (name);
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}
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public static URL getSystemResource(String name) {
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return getSystemClassLoader().getResource (name);
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}
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|
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/**
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* Return an InputStream representing the resource name.
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|
* This is essentially like
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* <code>getResource(name).openStream()</code>, except
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* it masks out any IOException and returns null on failure.
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* @param name resource to load
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* @return an InputStream, or null
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* @see java.lang.ClassLoader#getResource(String)
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* @see java.io.InputStream
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*/
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public InputStream getResourceAsStream(String name)
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{
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try {
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URL res = getResource (name);
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if (res == null) return null;
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return res.openStream ();
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} catch (java.io.IOException x) {
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return null;
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}
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}
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|
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/**
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* Return an java.io.URL representing the resouce <code>name</code>.
|
|
* The default implementation just returns <code>null</code>.
|
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* @param name resource to load
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* @return a URL, or null if there is no such resource.
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* @see java.lang.ClassLoader#getResourceAsBytes(String)
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* @see java.lang.ClassLoader#getResourceAsStream(String)
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* @see java.io.URL
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*/
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public URL getResource (String name)
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{
|
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// The rules say search the parent class if non-null,
|
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// otherwise search the built-in class loader (assumed to be
|
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// the system ClassLoader). If not found, call
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// findResource().
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URL result = null;
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|
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ClassLoader delegate = parent;
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|
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if (delegate == null)
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delegate = getSystemClassLoader ();
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|
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// Protect ourselves from looping.
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if (this != delegate)
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result = delegate.getResource (name);
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|
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if (result != null)
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return result;
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else
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return findResource (name);
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}
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|
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protected URL findResource (String name)
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|
{
|
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// Default to returning null. Derived classes implement this.
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return null;
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}
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|
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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);
|
|
}
|
|
|
|
protected Enumeration findResources (String name) throws IOException
|
|
{
|
|
// Default to returning null. Derived classes implement this.
|
|
return null;
|
|
}
|
|
}
|