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
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 *
 * 5. Products derived from this software may not be called "Apache",
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 *
 * 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;
import org.aspectj.apache.bcel.util.ClassLoaderRepository.SoftHashMap.SpecialValue;

/**
 * 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 1.13 2009/09/09 19:56:20 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 ClassLoaderReference loaderRef;

	// Choice of cache...
	private WeakHashMap /* <URL,SoftRef(JavaClass)> */<URL, SoftReference<JavaClass>> localCache = new WeakHashMap<URL, SoftReference<JavaClass>>();
	private static SoftHashMap /* <URL,JavaClass> */sharedCache = new SoftHashMap(Collections
			.synchronizedMap(new HashMap<Object, SpecialValue>()));

	// 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.loaderRef = new DefaultClassLoaderReference((loader != null) ? loader : getBootClassLoader());
	}

	public ClassLoaderRepository(ClassLoaderReference loaderRef) {
		this.loaderRef = loaderRef;
	}

	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<Object, SpecialValue> map;
		boolean recordMiss = true; // only interested in recording miss stats sometimes
		private ReferenceQueue rq = new ReferenceQueue();

		public SoftHashMap(Map<Object, SpecialValue> 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);
			}
		}

		@Override
		public Object get(Object key) {
			SpecialValue value = 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();
			}
		}

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

		@Override
		public Set entrySet() {
			return map.entrySet();
		}

		@Override
		public void clear() {
			processQueue();
			map.clear();
		}

		@Override
		public int size() {
			processQueue();
			return map.size();
		}

		@Override
		public Object remove(Object k) {
			processQueue();
			SpecialValue value = 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<JavaClass>(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 = loaderRef.getClassLoader().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 - unable to determine URL");

		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() : loaderRef.getClassLoader().getResourceAsStream(
					classFile + ".class"));
			if (is == null) {
				throw new ClassNotFoundException(className + " not found using url " + url);
			}
			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();
	}

}