package com.sun.org.apache.bcel.internal.util;
/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Apache" and "Apache Software Foundation" and
* "Apache BCEL" must not be used to endorse or promote products
* derived from this software without prior written permission. For
* written permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* "Apache BCEL", nor may "Apache" appear in their name, without
* prior written permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*/
import java.util.Hashtable;
import java.io.*;
import java.util.zip.*;
import com.sun.org.apache.bcel.internal.*;
import com.sun.org.apache.bcel.internal.classfile.*;
import com.sun.org.apache.bcel.internal.generic.*;
/**
* <p>Drop in replacement for the standard class loader of the JVM. You can use it
* in conjunction with the JavaWrapper to dynamically modify/create classes
* as they're requested.</p>
*
* <p>This class loader recognizes special requests in a distinct
* format, i.e., when the name of the requested class contains with
* "$$BCEL$$" it calls the createClass() method with that name
* (everything bevor the $$BCEL$$ is considered to be the package
* name. You can subclass the class loader and override that
* method. "Normal" classes class can be modified by overriding the
* modifyClass() method which is called just before defineClass().</p>
*
* <p>There may be a number of packages where you have to use the default
* class loader (which may also be faster). You can define the set of packages
* where to use the system class loader in the constructor. The default value contains
* "java.", "sun.", "javax."</p>
*
* @version $Id: ClassLoader.java,v 1.1.1.1 2001/10/29 20:00:29 jvanzyl Exp $
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
* @see JavaWrapper
* @see ClassPath
*/
public class ClassLoader extends java.lang.ClassLoader {
private Hashtable classes = new Hashtable(); // Hashtable is synchronized thus thread-safe
private String[] ignored_packages = {
"java.", "javax.", "sun."
};
public ClassLoader() {
}
/** @param ignored_packages classes contained in these packages will be loaded
* with the system class loader
*/
public ClassLoader(String[] ignored_packages) {
String[] new_p = new String[ignored_packages.length + this.ignored_packages.length];
System.arraycopy(this.ignored_packages, 0, new_p, 0, this.ignored_packages.length);
System.arraycopy(ignored_packages, 0, new_p, this.ignored_packages.length,
ignored_packages.length);
this.ignored_packages = new_p;
}
protected Class loadClass(String class_name, boolean resolve)
throws ClassNotFoundException
{
Class cl = null;
/* First try: lookup hash table.
*/
if((cl=(Class)classes.get(class_name)) == null) {
/* Second try: Load system class using system class loader. You better
* don't mess around with them.
*/
for(int i=0; i < ignored_packages.length; i++) {
if(class_name.startsWith(ignored_packages[i])) {
cl = Class.forName(class_name);
break;
}
}
if(cl == null) {
JavaClass clazz = null;
/* Third try: Special request?
*/
if(class_name.indexOf("$$BCEL$$") >= 0)
clazz = createClass(class_name);
else // Fourth try: Load classes via repository
clazz = modifyClass(Repository.lookupClass(class_name));
if(clazz != null) {
byte[] bytes = clazz.getBytes();
cl = defineClass(class_name, bytes, 0, bytes.length);
} else // Fourth try: Use default class loader
cl = Class.forName(class_name);
}
if(resolve)
resolveClass(cl);
}
classes.put(class_name, cl);
return cl;
}
/** Override this method if you want to alter a class before it gets actually
* loaded. Does nothing by default.
*/
protected JavaClass modifyClass(JavaClass clazz) {
return clazz;
}
/**
* Override this method to create you own classes on the fly. The
* name contains the special token $$BCEL$$. Everything before that
* token is consddered to be a package name. You can encode you own
* arguments into the subsequent string. You must regard however not
* to use any "illegal" characters, i.e., characters that may not
* appear in a Java class name too<br>
*
* The default implementation interprets the string as a encoded compressed
* Java class, unpacks and decodes it with the Utility.decode() method, and
* parses thee resulting byte array and returns the resulting JavaClass object.
*
* @param class_name compressed byte code with "$$BCEL$$" in it
*/
protected JavaClass createClass(String class_name) {
int index = class_name.indexOf("$$BCEL$$");
String real_name = class_name.substring(index + 8);
JavaClass clazz = null;
try {
byte[] bytes = Utility.decode(real_name, true);
ClassParser parser = new ClassParser(new ByteArrayInputStream(bytes), "foo");
clazz = parser.parse();
} catch(Throwable e) {
e.printStackTrace();
return null;
}
// Adapt the class name to the passed value
ConstantPool cp = clazz.getConstantPool();
ConstantClass cl = (ConstantClass)cp.getConstant(clazz.getClassNameIndex(),
Constants.CONSTANT_Class);
ConstantUtf8 name = (ConstantUtf8)cp.getConstant(cl.getNameIndex(),
Constants.CONSTANT_Utf8);
name.setBytes(class_name.replace('.', '/'));
return clazz;
}
}
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