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Basic classloader framework
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package org.sapia.clazzy;

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ResourceBundle;

import org.sapia.clazzy.loader.FileSystemLoader;
import org.sapia.clazzy.loader.JarLoader;
import org.sapia.clazzy.loader.Loader;

/**
 * This classloader delegates class lookups the Loader instances
 * that it encapsulates. Children are added through the addLoader() 
 * or addFile method.
 * 
 * The CompositeClassLoaderBuilder can conveniently be used to create
 * an instance of this class. 
 * 
 * @see org.sapia.clazzy.CompositeClassLoaderBuilder
 * 
 * @author Yanick Duchesne
 * 
 * 

 * Copyright: 
 * 
Copyright © 2002-2004 Sapia Open
 * Source Software . All Rights Reserved.
 * 
 * License: 
 * 
Read the license.txt file of the jar or visit the license page  at the Sapia
 * OSS web site
 * 
 * 
 */
public class CompositeClassLoader extends BaseClassLoader implements Consts{

  private List           _loaders = Collections.synchronizedList(new ArrayList());
  private LoaderSelector _selector;
  private ResourceBundle _bundle;

  public CompositeClassLoader(ClassLoader parent, LoaderSelector selector) {
    super(parent);
    _selector = selector;
  }

  public CompositeClassLoader(LoaderSelector selector) {
    _selector = selector;
  }
  
  /**
   * @return the URLs to which this instance "points".
   */
  public URL[] getURLs(){
    List urls = new ArrayList();
    Loader loader;
    for(int i = 0; i < _loaders.size(); i++){
      loader = (Loader)_loaders.get(i);
      if(loader instanceof URLEnabled){
        try{
          urls.add(((URLEnabled)loader).getURL());
        }catch(MalformedURLException e){
        }
      }
    }
    return (URL[])urls.toArray(new URL[urls.size()]);
  }

  /**
   * @see java.lang.ClassLoader#findClass(java.lang.String)
   */
  public Class findClass(String name) throws ClassNotFoundException {
    Class clazz = null;
    Loader loader;
    byte[] classBytes = null;
    String resourceName = name.replace('.', '/')+".class";
    synchronized(_loaders) {
      for(int i = 0; i < _loaders.size(); i++) {
        loader = (Loader) _loaders.get(i);
        if(_selector.acceptsClass(name, loader)) {
          classBytes = loader.loadBytes(resourceName);
          if(classBytes != null){
            break;
          }
        }
      }
    }
    if(classBytes == null) {
      throw new ClassNotFoundException(name);
    }
    String pckg = Utils.getPackageNameFor(name);    
    if(pckg != null && getPackage(pckg) == null){
      definePackage(pckg, 
                    PACKAGE_SPEC_TITLE,
                    PACKAGE_SPEC_VERSION,
                    PACKAGE_SPEC_VENDOR,
                    PACKAGE_IMPL_TITLE,
                    PACKAGE_IMPL_VERSION,
                    PACKAGE_IMPL_VENDOR, 
                    null);       
    }
    return super.defineClass(name, classBytes, 0, classBytes.length);
  }
  
  /**
   * @see java.lang.ClassLoader#findResource(java.lang.String)
   */
  protected URL findResource(String name) {
    Loader loader;
    URL toReturn = null;
    synchronized(_loaders) {
      for(int i = 0; i < _loaders.size(); i++) {
        loader = (Loader) _loaders.get(i);
        if(_selector.acceptsResource(name, loader)) {
          toReturn = loader.getURL(name);
          if(toReturn != null){
            break;
          }
        }
      }
    }
    return toReturn;
  }
  
  /**
   * @param loader
   *          the Loader to add to this instance.
   */
  public void addLoader(Loader loader) {
    _loaders.add(loader);
  }
  
  /**
   * Adds the file object corresponding to a directory of classes or
   * a jar to this instance.
   * 
   * Internally, the method creates either a FileSystemLoader 
   * (if the given file object corresponds to a directory) or a JarLoader.
   * @param file a File
   */
  public void addPath(File file){
    if(!file.exists()){
      return;
    }
    if(file.isDirectory()){
      addLoader(new FileSystemLoader(file));
    }
    else{
      addLoader(new JarLoader(file));
    }
  }
  
  /**
   * Releases all resources that this instance.
   */
  public void close(){
    Loader loader;
    for(int i = 0; i < _loaders.size(); i++){
      loader = (Loader)_loaders.get(i);
      try{
        loader.close();
      }catch(Exception e){}
    }
  }
  
}