org.aspectj/bcel-builder/src/org/aspectj/apache/bcel/util/ClassLoaderRepository.java

package org.aspectj.apache.bcel.util;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Apache" and "Apache Software Foundation" and
 *    "Apache BCEL" must not be used to endorse or promote products
 *    derived from this software without prior written permission. For
 *    written permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    "Apache BCEL", nor may "Apache" appear in their name, without
 *    prior written permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.AbstractMap;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;
import java.util.WeakHashMap;

import org.aspectj.apache.bcel.classfile.ClassParser;
import org.aspectj.apache.bcel.classfile.JavaClass;

/**
 * The repository maintains information about which classes have
 * been loaded.
 *
 * It loads its data from the ClassLoader implementation
 * passed into its constructor.
 *
 * @see org.aspectj.apache.bcel.Repository
 *
 * @version $Id: ClassLoaderRepository.java,v 1.8 2006/08/21 15:23:58 aclement Exp $
 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
 * @author David Dixon-Peugh
 */
public class ClassLoaderRepository implements Repository {
  private static java.lang.ClassLoader bootClassLoader = null;
  private java.lang.ClassLoader loader;
  
  // Choice of cache...
  private         WeakHashMap /*<URL,SoftRef(JavaClass)>*/localCache = new WeakHashMap(); 
  private static SoftHashMap /*<URL,JavaClass>*/sharedCache = new SoftHashMap(Collections.synchronizedMap(new HashMap()));
  
  // For fast translation of the classname *intentionally not static*
  private SoftHashMap /*<String,URL>*/ nameMap = new SoftHashMap(new HashMap(), false);
  
  public static boolean useSharedCache = 
	  System.getProperty("org.aspectj.apache.bcel.useSharedCache","true").equalsIgnoreCase("true");
  
  private static int  cacheHitsShared    = 0;
  private static int  missSharedEvicted  = 0; // Misses in shared cache access due to reference GC
  private long timeManipulatingURLs = 0L; 
  private long timeSpentLoading     = 0L;
  private int  classesLoadedCount = 0;
  private int  misses             = 0;
  private int  cacheHitsLocal     = 0;
  private int  missLocalEvicted   = 0; // Misses in local cache access due to reference GC

  public ClassLoaderRepository( java.lang.ClassLoader loader ) {
      this.loader = (loader != null) ? loader : getBootClassLoader();
  }
  
  private static synchronized java.lang.ClassLoader getBootClassLoader() {
	  if (bootClassLoader == null) {
		  bootClassLoader = new URLClassLoader(new URL[0]);
	  }
	  return bootClassLoader;
  }
  
  // Can track back to its key
  public static class SoftHashMap extends AbstractMap {
	  private Map map;
	  boolean recordMiss = true; // only interested in recording miss stats sometimes
	  private ReferenceQueue rq = new ReferenceQueue(); 
	  
      public SoftHashMap(Map map) { this.map = map; }
	  public SoftHashMap() { this(new HashMap()); }
	  public SoftHashMap(Map map, boolean b) { this(map); this.recordMiss=b;}
	
	  class SpecialValue extends SoftReference {
		  private final Object key;
		  SpecialValue(Object k,Object v) {
		    super(v,rq);
		    this.key = k;
		  }
	  }  

	  private void processQueue() {
		SpecialValue sv = null;
		while ((sv = (SpecialValue)rq.poll())!=null) {
			map.remove(sv.key);
		}
	  }
	
	  public Object get(Object key) {
		SpecialValue value = (SpecialValue)map.get(key);
		if (value==null) return null;
		if (value.get()==null) {
			// it got GC'd
			map.remove(value.key);
			if (recordMiss) missSharedEvicted++;
			return null;
		} else {
			return value.get();
		}
	  }

	  public Object put(Object k, Object v) {
		processQueue();
		return map.put(k, new SpecialValue(k,v));
	  }

	  public Set entrySet() {
		return map.entrySet();
	  }
	
	  public void clear() {
		processQueue();
		map.clear();
	  }
	
	  public int size() {
		processQueue();
		return map.size();
	  }
	
	  public Object remove(Object k) {
		processQueue();
		SpecialValue value = (SpecialValue)map.remove(k);
		if (value==null) return null;
		if (value.get()!=null) {
			return value.get();
		}
		return null;
	  }
  }

  /**
   * Store a new JavaClass into this repository as a soft reference and return the reference
   */
  private void storeClassAsReference(URL url, JavaClass clazz ) {
	if (useSharedCache) {
		clazz.setRepository(null); // can't risk setting repository, we'll get in a pickle!
		sharedCache.put(url, clazz);
	} else {
	    clazz.setRepository(this);
		localCache.put(url, new SoftReference(clazz));
	}
  }
  
  /**
   * Store a new JavaClass into this Repository.
   */
  public void storeClass( JavaClass clazz ) {
	  storeClassAsReference(toURL(clazz.getClassName()),clazz);
  }

  /**
   * Remove class from repository
   */
  public void removeClass(JavaClass clazz) {
    if (useSharedCache) sharedCache.remove(toURL(clazz.getClassName()));
    else                localCache.remove(toURL(clazz.getClassName()));
  }

  /**
   * Find an already defined JavaClass in the local cache.
   */
  public JavaClass findClass( String className ) {
	  if (useSharedCache) return findClassShared(toURL(className));
	  else                return findClassLocal(toURL(className));
  }
  
  private JavaClass findClassLocal( URL url ) {
    Object o = localCache.get(url);
    if (o != null) {
    	o = ((Reference)o).get();
    	if (o != null) {
    		return (JavaClass)o;
    	} else {
    		missLocalEvicted++;
    	}
    }
    return null;
  }
  
  /**
   * Find an already defined JavaClass in the shared cache.
   */
  private JavaClass findClassShared(URL url) {
	  return (JavaClass)sharedCache.get(url);
  }

  private URL toURL(String className) {
	  URL url = (URL)nameMap.get(className);
	  if (url==null) {
		  String classFile = className.replace('.', '/');
	      url = loader.getResource( classFile + ".class" );
	      nameMap.put(className, url);
	  }
      return url;
  }
  
  /**
   * Lookup a JavaClass object from the Class Name provided.
   */
  public JavaClass loadClass( String className ) throws ClassNotFoundException {
    
	// translate to a URL
	long time = System.currentTimeMillis();
    java.net.URL url = toURL(className);
	timeManipulatingURLs += (System.currentTimeMillis() - time);
	if (url==null) throw new ClassNotFoundException(className + " not found.");
    
	JavaClass clazz = null;

	// Look in the appropriate cache
	if (useSharedCache) {
		clazz = findClassShared(url);
		if (clazz != null) { cacheHitsShared++; return clazz; } 	
	} else {
	    clazz = findClassLocal(url);
	    if (clazz != null) { cacheHitsLocal++; return clazz; }
	}
    
	// Didn't find it in either cache
	misses++;

    try {    	
    	// Load it
	    String classFile = className.replace('.', '/');
		InputStream is = (useSharedCache?url.openStream():loader.getResourceAsStream( classFile + ".class" ));
	    if (is == null) { 
		  throw new ClassNotFoundException(className + " not found.");
	    }
		ClassParser parser = new ClassParser( is, className );
        clazz = parser.parse();
	    
        // Cache it
        storeClassAsReference(url, clazz );

        timeSpentLoading += (System.currentTimeMillis() - time);
	    classesLoadedCount++;
        return clazz;
    } catch (IOException e) {
      throw new ClassNotFoundException( e.toString() );
    }
  }
  

  /**
   * Produce a report on cache usage.
   */
  public String report() {
	  StringBuffer sb = new StringBuffer();
	  sb.append("BCEL repository report.");
	  if (useSharedCache) sb.append(" (shared cache)");
	  else                sb.append(" (local cache)");
	  sb.append(" Total time spent loading: "+timeSpentLoading+"ms.");
	  sb.append(" Time spent manipulating URLs: "+timeManipulatingURLs+"ms.");
	  sb.append(" Classes loaded: "+classesLoadedCount+".");
	  if (useSharedCache) {
		  sb.append(" Shared cache size: "+sharedCache.size());
	      sb.append(" Shared cache (hits/missDueToEviction): ("+cacheHitsShared+"/"+missSharedEvicted+").");
	  } else {
		  sb.append(" Local cache size: "+localCache.size());
		  sb.append(" Local cache (hits/missDueToEviction): ("+cacheHitsLocal+"/"+missLocalEvicted+").");
	  }
	  return sb.toString();
  }
  
  /**
   * Returns an array of the stats, for testing, the order is fixed:
   * 0=time spent loading (static)
   * 1=time spent manipulating URLs (static)
   * 2=classes loaded (static)
   * 3=cache hits shared (static)
   * 4=misses in shared due to eviction (static)
   * 5=cache hits local
   * 6=misses in local due to eviction
   * 7=shared cache size
   */
  public long[] reportStats() {
	  return new long[]{timeSpentLoading,timeManipulatingURLs,classesLoadedCount,
			             cacheHitsShared,missSharedEvicted,cacheHitsLocal,missLocalEvicted,
			             sharedCache.size()};
  }
  
  /**
   * Reset statistics and clear all caches
   */
  public void reset() {
	  timeManipulatingURLs = 0L; 
	  timeSpentLoading = 0L;
	  classesLoadedCount = 0;
	  cacheHitsLocal    = 0;
	  cacheHitsShared   = 0;
	  missSharedEvicted = 0; 
	  missLocalEvicted  = 0; 
	  misses = 0;
	  clear();
  }
  
  
  public JavaClass loadClass(Class clazz) throws ClassNotFoundException {
    return loadClass(clazz.getName());
  }

  /** Clear all entries from the local cache */
  public void clear() {
	  if (useSharedCache) sharedCache.clear();
	  else                localCache.clear();
  }
  
}