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ShrinkWrap Extension for creating a ClassLoader based on a Archive
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/*
 * JBoss, Home of Professional Open Source
 * Copyright 2009, Red Hat Middleware LLC, and individual contributors
 * by the @authors tag. See the copyright.txt in the distribution for a
 * full listing of individual contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * http://www.apache.org/licenses/LICENSE-2.0
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.jboss.shrinkwrap.classloader;

import java.io.Closeable;
import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLConnection;
import java.net.URLStreamHandler;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;

import org.jboss.shrinkwrap.api.Archive;
import org.jboss.shrinkwrap.api.ArchivePath;
import org.jboss.shrinkwrap.api.ArchivePaths;

/**
 * Extension that will create a ClassLoader based on a Array of Archives
 *
 * @author Aslak Knutsen
 * @author ALR
 */
public class ShrinkWrapClassLoader extends URLClassLoader implements Closeable
{
   //-------------------------------------------------------------------------------------||
   // Class Members ----------------------------------------------------------------------||
   //-------------------------------------------------------------------------------------||

   /**
    * Logger
    */
   private static final Logger log = Logger.getLogger(ShrinkWrapClassLoader.class.getName());

   //-------------------------------------------------------------------------------------||
   // Instance Members -------------------------------------------------------------------||
   //-------------------------------------------------------------------------------------||

   /**
    * Map of all streams opened, such that they may be closed in {@link ShrinkWrapClassLoader#close()}.
    * Guarded by "this".
    */
   private final ConcurrentMap openedStreams = new ConcurrentHashMap();

   //-------------------------------------------------------------------------------------||
   // Constructors -----------------------------------------------------------------------||
   //-------------------------------------------------------------------------------------||

   /**
    * Constructs a new ShrinkWrapClassLoader for the specified {@link Archive}s using the
    * default delegation parent ClassLoader. The {@link Archive}s will
    * be searched in the order specified for classes and resources after
    * first searching in the parent class loader.
    * 
    * @param archives the {@link Archive}s from which to load classes and resources
    */
   public ShrinkWrapClassLoader(final Archive... archives)
   {
      super(new URL[]
      {});

      if (archives == null)
      {
         throw new IllegalArgumentException("Archives must be specified");
      }
      addArchives(archives);
   }

   /**
    * Constructs a new ShrinkWrapClassLoader for the given {@link Archive}s. The {@link Archive}s will be
    * searched in the order specified for classes and resources after first
    * searching in the specified parent class loader. 
    * 
    * @param parent the parent class loader for delegation
    * @param archives the {@link Archive}s from which to load classes and resources
    */
   public ShrinkWrapClassLoader(final ClassLoader parent, final Archive... archives)
   {
      super(new URL[]
      {}, parent);

      if (archives == null)
      {
         throw new IllegalArgumentException("Archives must be specified");
      }
      addArchives(archives);
   }

   private void addArchives(final Archive[] archives)
   {
      for (final Archive archive : archives)
      {
         addArchive(archive);
      }
   }

   private void addArchive(final Archive archive)
   {
      try
      {
         addURL(new URL(null, "archive:" + archive.getName() + "/", new URLStreamHandler()
         {
            @Override
            protected URLConnection openConnection(final URL u) throws IOException
            {
               return new URLConnection(u)
               {
                  @Override
                  public void connect() throws IOException
                  {
                  }

                  @Override
                  public InputStream getInputStream() throws IOException
                  {
                     synchronized (this)
                     {
                        InputStream input = openedStreams.get(u);
                        if (input == null)
                        {
                           ArchivePath path = convertToArchivePath(u);
                           input = archive.get(path).getAsset().openStream();
                           openedStreams.put(u, input);
                        }
                        return input;
                     }
                  }

                  private ArchivePath convertToArchivePath(URL url)
                  {
                     String path = url.getPath();
                     path = path.replace(archive.getName(), "");

                     return ArchivePaths.create(path);
                  }
               };
            }
         }));
      }
      catch (Exception e)
      {
         throw new RuntimeException("Could not create URL for archive: " + archive.getName(), e);
      }
   }

   public void close() throws IOException
   {
      synchronized (this)
      {
         for (InputStream stream : openedStreams.values())
         {
            try
            {
               stream.close();
            }
            catch (Exception e)
            {
               log.warning("Could not close opened inputstream: " + e);
            }
         }
         openedStreams.clear();
      }
   }
}