    001// Copyright 2006-2013 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.tapestry5.ioc.internal.util;
    016
    017import org.apache.tapestry5.ioc.Resource;
    018
    019import java.net.URL;
    020
    021/**
    022 * Implementation of {@link Resource} for files on the classpath (as defined by a {@link ClassLoader}).
    023 */
    024public final class ClasspathResource extends AbstractResource
    025{
    026    private final ClassLoader classLoader;
    027
    028    // Guarded by lock
    029    private URL url;
    030
    031    // Guarded by lock
    032    private boolean urlResolved;
    033
    034    public ClasspathResource(String path)
    035    {
    036        this(Thread.currentThread().getContextClassLoader(), path);
    037    }
    038
    039    public ClasspathResource(ClassLoader classLoader, String path)
    040    {
    041        super(path);
    042        assert classLoader != null;
    043
    044        this.classLoader = classLoader;
    045    }
    046
    047    @Override
    048    protected Resource newResource(String path)
    049    {
    050        return new ClasspathResource(classLoader, path);
    051    }
    052
    053    @Override
    054    public URL toURL()
    055    {
    056        try
    057        {
    058            acquireReadLock();
    059
    060            if (!urlResolved)
    061            {
    062                resolveURL();
    063            }
    064
    065            return url;
    066        } finally
    067        {
    068            releaseReadLock();
    069        }
    070    }
    071
    072    private void resolveURL()
    073    {
    074        try
    075        {
    076            upgradeReadLockToWriteLock();
    077
    078            if (!urlResolved)
    079            {
    080                url = classLoader.getResource(getPath());
    081
    082                validateURL(url);
    083
    084                urlResolved = true;
    085            }
    086        } finally
    087        {
    088            downgradeWriteLockToReadLock();
    089        }
    090
    091
    092    }
    093
    094    @Override
    095    public boolean equals(Object obj)
    096    {
    097        if (obj == null) return false;
    098
    099        if (obj == this) return true;
    100
    101        if (obj.getClass() != getClass()) return false;
    102
    103        ClasspathResource other = (ClasspathResource) obj;
    104
    105        return other.classLoader == classLoader && other.getPath().equals(getPath());
    106    }
    107
    108    @Override
    109    public int hashCode()
    110    {
    111        return 227 ^ getPath().hashCode();
    112    }
    113
    114    @Override
    115    public String toString()
    116    {
    117        return "classpath:" + getPath();
    118    }
    119
    120}