001    // Copyright 2006, 2007, 2008, 2012 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    
015    package org.apache.tapestry5.ioc.internal.util;
016    
017    import org.apache.tapestry5.ioc.Resource;
018    
019    import java.net.URL;
020    
021    /**
022     * Implementation of {@link Resource} for files on the classpath (as defined by a {@link ClassLoader}).
023     */
024    public 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        public URL toURL()
054        {
055            try
056            {
057                acquireReadLock();
058    
059                if (!urlResolved)
060                {
061                    resolveURL();
062                }
063    
064                return url;
065            } finally
066            {
067                releaseReadLock();
068            }
069        }
070    
071        private void resolveURL()
072        {
073            try
074            {
075                upgradeReadLockToWriteLock();
076    
077                if (!urlResolved)
078                {
079                    url = classLoader.getResource(getPath());
080                    urlResolved = true;
081                }
082            } finally
083            {
084                downgradeWriteLockToReadLock();
085            }
086        }
087    
088        @Override
089        public boolean equals(Object obj)
090        {
091            if (obj == null) return false;
092    
093            if (obj == this) return true;
094    
095            if (obj.getClass() != getClass()) return false;
096    
097            ClasspathResource other = (ClasspathResource) obj;
098    
099            return other.classLoader == classLoader && other.getPath().equals(getPath());
100        }
101    
102        @Override
103        public int hashCode()
104        {
105            return 227 ^ getPath().hashCode();
106        }
107    
108        @Override
109        public String toString()
110        {
111            return "classpath:" + getPath();
112        }
113    
114    }