javassist/src/main/javassist/LoaderClassPath.java

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2003 Shigeru Chiba. All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 */
package javassist;

import java.io.InputStream;
import java.lang.ref.WeakReference;

/**
 * A class search-path representing a class loader.
 *
 * <p>It is used for obtaining a class file from the given
 * class loader by <code>getResourceAsStream()</code>.
 * The <code>LoaderClassPath</code> refers to the class loader through
 * <code>WeakReference</code>.  If the class loader is garbage collected,
 * the other search pathes are examined.
 *
 * @author <a href="mailto:bill@jboss.org">Bill Burke</a>
 * @author Shigeru Chiba
 *
 * @see javassist.ClassPath
 * @see ClassPool#insertClassPath(ClassPath)
 * @see ClassPool#appendClassPath(ClassPath)
 */
public class LoaderClassPath implements ClassPath {
    private WeakReference clref;

    /**
     * Creates a search path representing a class loader.
     */
    public LoaderClassPath(ClassLoader cl) {
        clref = new WeakReference(cl);
    }

    public String toString() {
        Object cl = null;
        if (clref != null)
            cl = clref.get();

        return cl == null ? "<null>" : cl.toString();
    }

    /**
     * Obtains a class file from the class loader.
     */
    public InputStream openClassfile(String classname) {
        String cname = classname.replace('.', '/') + ".class";
        ClassLoader cl = (ClassLoader)clref.get();
        if (cl == null)
            return null;        // not found
        else
            return cl.getResourceAsStream(cname);
    }

    /**
     * Closes this class path.
     */
    public void close() {
        clref = null;
    }
}