/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999- Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later,
 * or the Apache License Version 2.0.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist;

import java.io.InputStream;
import java.lang.ref.Reference;
import java.lang.ref.WeakReference;
import java.net.URL;

A class search-path representing a class loader.
It is used for obtaining a class file from the given
class loader by getResourceAsStream().
The LoaderClassPath refers to the class loader through
WeakReference.  If the class loader is garbage collected,
the other search pathes are examined.
The given class loader must have both getResourceAsStream()
and getResource().
Class files in a named module are private to that module.
This method cannot obtain class files in named modules.

Author:
Bill Burke, Shigeru Chiba
See Also:
ClassPool.insertClassPath(ClassPath)
ClassPool.appendClassPath(ClassPath)
ClassClassPath/**
 * 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.
 *
 * <p>The given class loader must have both <code>getResourceAsStream()</code>
 * and <code>getResource()</code>.
 * 
 * <p>Class files in a named module are private to that module.
 * This method cannot obtain class files in named modules.
 * </p>
 *
 * @author <a href="mailto:bill@jboss.org">Bill Burke</a>
 * @author Shigeru Chiba
 *
 * @see ClassPool#insertClassPath(ClassPath)
 * @see ClassPool#appendClassPath(ClassPath)
 * @see ClassClassPath
 */
public class LoaderClassPath implements ClassPath {
    private Reference<ClassLoader> clref;

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

    @Override
    public String toString() {
        return clref.get() == null ? "<null>" : clref.get().toString();
    }

    
Obtains a class file from the class loader.
This method calls getResourceAsStream(String)
on the class loader.
/**
     * Obtains a class file from the class loader.
     * This method calls <code>getResourceAsStream(String)</code>
     * on the class loader.
     */
    @Override
    public InputStream openClassfile(String classname) throws NotFoundException {
        String cname = classname.replace('.', '/') + ".class";
        ClassLoader cl = clref.get();
        if (cl == null)
            return null;        // not found
        InputStream is = cl.getResourceAsStream(cname);
        return is;
    }

    
Obtains the URL of the specified class file.
This method calls getResource(String)
on the class loader.
Returns:
null if the class file could not be found./**
     * Obtains the URL of the specified class file.
     * This method calls <code>getResource(String)</code>
     * on the class loader.
     *
     * @return null if the class file could not be found. 
     */
    @Override
    public URL find(String classname) {
        String cname = classname.replace('.', '/') + ".class";
        ClassLoader cl = clref.get();
        if (cl == null)
            return null;        // not found
        URL url = cl.getResource(cname);
        return url;
    }
}