001// Copyright 2004, 2005 The Apache Software Foundation
002//
003// Licensed under the Apache License, Version 2.0 (the "License");
004// you may not use this file except in compliance with the License.
005// You may obtain a copy of the License at
006//
007//     http://www.apache.org/licenses/LICENSE-2.0
008//
009// Unless required by applicable law or agreed to in writing, software
010// distributed under the License is distributed on an "AS IS" BASIS,
011// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012// See the License for the specific language governing permissions and
013// limitations under the License.
014
015package org.apache.hivemind.service.impl;
016
017import java.util.HashSet;
018import java.util.Set;
019
020import javassist.CannotCompileException;
021import javassist.ClassPath;
022import javassist.ClassPool;
023import javassist.CtClass;
024import javassist.LoaderClassPath;
025
026/**
027 * Used to ensure that {@link javassist.ClassPool#appendClassPath(javassist.ClassPath)} is invoked
028 * with a synchronized lock. Additionally, wraps around a shared
029 * {@link org.apache.hivemind.service.impl.ClassFactoryClassLoader}.
030 * 
031 * @author Howard Lewis Ship
032 */
033public class HiveMindClassPool extends ClassPool
034{
035    private ClassFactoryClassLoader _loader = new ClassFactoryClassLoader();
036
037    /**
038     * Used to identify which class loaders have already been integrated into the pool.
039     */
040    private Set _loaders = new HashSet();
041
042    public HiveMindClassPool()
043    {
044        super(null);
045
046        appendClassLoader(Thread.currentThread().getContextClassLoader());
047    }
048
049    /**
050     * Convienience method for adding to the ClassPath for a particular class loader.
051     */
052    public synchronized void appendClassLoader(ClassLoader loader)
053    {
054        if (loader == null || loader == _loader || _loaders.contains(loader))
055            return;
056
057        _loader.addDelegateLoader(loader);
058
059        ClassPath path = new LoaderClassPath(loader);
060
061        appendClassPath(path);
062
063        _loaders.add(loader);
064    }
065
066    /**
067     * Invoked to convert an fabricated class into a real class. The new classes' class loader will
068     * be the delegating ClassFactoryClassLoader, which has visibility to all class loaders for all
069     * modules.
070     * 
071     * @since 1.1
072     */
073    public Class toClass(CtClass ctClass) throws CannotCompileException
074    {
075        return ctClass.toClass(_loader);
076    }
077}