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The AspectJ weaver introduces advices to java classes
/*******************************************************************************
* Copyright (c) 2012 Contributors.
* All rights reserved.
* This program and the accompanying materials are made available
* under the terms of the Eclipse Public License v1.0
* which accompanies this distribution and is available at
* http://eclipse.org/legal/epl-v10.html
*
* Contributors:
* Lyor Goldstein (vmware) add support for weaved class being re-defined
*******************************************************************************/
package org.aspectj.weaver.tools.cache;
import java.io.File;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import org.aspectj.util.FileUtil;
import org.aspectj.util.LangUtil;
import org.aspectj.weaver.tools.Trace;
import org.aspectj.weaver.tools.TraceFactory;
/**
* Uses a background thread to do the actual I/O and for caching "persistence"
* so that the caching works faster on repeated activations of the application.
* The class maintains an in-memory cache, and uses a queue of {@link AsyncCommand}s
* to signal to a background thread various actions required to "synchronize"
* the in-memory cache with the persisted copy. Whenever there is a cache miss
* from the {@link #get(CachedClassReference)} call, the weaver issues a
* {@link #put(CachedClassEntry)} call. This call has 2 side-effects:
*
* -
* The in-memory cache is updated so that subsequent calls to {@link #get(CachedClassReference)}
* will not return the mapped value.
*
*
* -
* An "update index" {@link AsyncCommand} is posted to the background
* thread so that the newly mapped value will be persisted (eventually)
*
*
* The actual persistence is implemented by the concrete classes
*/
public abstract class AsynchronousFileCacheBacking extends AbstractIndexedFileCacheBacking {
private static final BlockingQueue commandsQ=new LinkedBlockingQueue();
private static final ExecutorService execService=Executors.newSingleThreadExecutor();
private static Future commandsRunner;
protected final Map index, exposedIndex;
protected final Map bytesMap, exposedBytes;
protected AsynchronousFileCacheBacking (File cacheDir) {
super(cacheDir);
index = readIndex(cacheDir, getIndexFile());
exposedIndex = Collections.unmodifiableMap(index);
bytesMap = readClassBytes(index, cacheDir);
exposedBytes = Collections.unmodifiableMap(bytesMap);
}
@Override
protected Map getIndex() {
return index;
}
public CachedClassEntry get(CachedClassReference ref, byte[] originalBytes) {
String key=ref.getKey();
final IndexEntry indexEntry;
synchronized(index) {
if ((indexEntry=index.get(key)) == null) {
return null;
}
}
if (crc(originalBytes) != indexEntry.crcClass) {
if ((logger != null) && logger.isTraceEnabled()) {
logger.debug("get(" + getCacheDirectory() + ") mismatched original class bytes CRC for " + key);
}
remove(key);
return null;
}
if (indexEntry.ignored) {
return new CachedClassEntry(ref, WeavedClassCache.ZERO_BYTES, CachedClassEntry.EntryType.IGNORED);
}
final byte[] bytes;
synchronized(bytesMap) {
/*
* NOTE: we assume that keys represent classes so if we have their
* bytes they will not be re-created
*/
if ((bytes=bytesMap.remove(key)) == null) {
return null;
}
}
if (indexEntry.generated) {
return new CachedClassEntry(ref, bytes, CachedClassEntry.EntryType.GENERATED);
} else {
return new CachedClassEntry(ref, bytes, CachedClassEntry.EntryType.WEAVED);
}
}
public void put(CachedClassEntry entry, byte[] originalBytes) {
String key=entry.getKey();
byte[] bytes=entry.isIgnored() ? null : entry.getBytes();
synchronized(index) {
IndexEntry indexEntry=index.get(key);
if (indexEntry != null) {
return;
}
/*
* Note: we do not cache the class bytes - only send them to
* be saved. The assumption is that the 'put' call was invoked
* because 'get' failed to return any bytes. And since we assume
* that each class bytes are required only once, there is no
* need to cache them
*/
indexEntry = createIndexEntry(entry, originalBytes);
index.put(key, indexEntry);
}
if (!postCacheCommand(new InsertCommand(this, key, bytes))) {
if ((logger != null) && logger.isTraceEnabled()) {
logger.error("put(" + getCacheDirectory() + ") Failed to post insert command for " + key);
}
}
if ((logger != null) && logger.isTraceEnabled()) {
logger.debug("put(" + getCacheDirectory() + ")[" + key + "] inserted");
}
}
public void remove(CachedClassReference ref) {
remove(ref.getKey());
}
protected IndexEntry remove (String key) {
IndexEntry entry;
synchronized(index) {
entry = index.remove(key);
}
synchronized(bytesMap) {
bytesMap.remove(key);
}
if (!postCacheCommand(new RemoveCommand(this, key))) {
if ((logger != null) && logger.isTraceEnabled()) {
logger.error("remove(" + getCacheDirectory() + ") Failed to post remove command for " + key);
}
}
if (entry != null) {
if (!key.equals(entry.key)) {
if ((logger != null) && logger.isTraceEnabled()) {
logger.error("remove(" + getCacheDirectory() + ") Mismatched keys: " + key + " / " + entry.key);
}
} else if ((logger != null) && logger.isTraceEnabled()) {
logger.debug("remove(" + getCacheDirectory() + ")[" + key + "] removed");
}
}
return entry;
}
public List getIndexEntries () {
synchronized(index) {
if (index.isEmpty()) {
return Collections.emptyList();
} else {
return new ArrayList(index.values());
}
}
}
public Map getIndexMap () {
return exposedIndex;
}
public Map getBytesMap () {
return exposedBytes;
}
public void clear() {
synchronized(index) {
index.clear();
}
if (!postCacheCommand(new ClearCommand(this))) {
if ((logger != null) && logger.isTraceEnabled()) {
logger.error("Failed to post clear command for " + getIndexFile());
}
}
}
protected void executeCommand (AsyncCommand cmd) throws Exception {
if (cmd instanceof ClearCommand) {
executeClearCommand();
} else if (cmd instanceof UpdateIndexCommand) {
executeUpdateIndexCommand();
} else if (cmd instanceof InsertCommand) {
executeInsertCommand((InsertCommand) cmd);
} else if (cmd instanceof RemoveCommand) {
executeRemoveCommand((RemoveCommand) cmd);
} else {
throw new UnsupportedOperationException("Unknown command: " + cmd);
}
}
protected void executeClearCommand () throws Exception {
FileUtil.deleteContents(getIndexFile());
FileUtil.deleteContents(getCacheDirectory());
}
protected void executeUpdateIndexCommand () throws Exception {
writeIndex(getIndexFile(), getIndexEntries());
}
protected void executeInsertCommand (InsertCommand cmd) throws Exception {
writeIndex(getIndexFile(), getIndexEntries());
byte[] bytes=cmd.getClassBytes();
if (bytes != null) {
writeClassBytes(cmd.getKey(), bytes);
}
}
protected void executeRemoveCommand (RemoveCommand cmd) throws Exception {
Exception err=null;
try {
removeClassBytes(cmd.getKey());
} catch(Exception e) {
err = e;
}
writeIndex(getIndexFile(), getIndexEntries());
if (err != null) {
throw err; // check if the class bytes remove had any problems
}
}
/**
* Helper for {@link #executeRemoveCommand(RemoveCommand)}
* @param key The key representing the class whose bytes are to be removed
* @throws Exception if failed to remove class bytes
*/
protected abstract void removeClassBytes (String key) throws Exception;
protected abstract Map readClassBytes (Map indexMap, File cacheDir);
@Override
public String toString() {
return getClass().getSimpleName() + "[" + String.valueOf(getCacheDirectory()) + "]";
}
protected static final T createBacking (
File cacheDir, AsynchronousFileCacheBackingCreator creator) {
final Trace trace=TraceFactory.getTraceFactory().getTrace(AsynchronousFileCacheBacking.class);
if (!cacheDir.exists()) {
if (!cacheDir.mkdirs()) {
if ((trace != null) && trace.isTraceEnabled()) {
trace.error("Unable to create cache directory at " + cacheDir.getAbsolutePath());
}
return null;
}
}
if (!cacheDir.canWrite()) {
if ((trace != null) && trace.isTraceEnabled()) {
trace.error("Cache directory is not writable at " + cacheDir.getAbsolutePath());
}
return null;
}
// start the service (if needed) only if successfully create the backing instance
T backing=creator.create(cacheDir);
synchronized(execService) {
if (commandsRunner == null) {
commandsRunner = execService.submit(new Runnable() {
@SuppressWarnings("synthetic-access")
public void run() {
for ( ; ; ) {
try {
AsyncCommand cmd=commandsQ.take();
try {
AsynchronousFileCacheBacking cache=cmd.getCache();
cache.executeCommand(cmd);
} catch(Exception e) {
if ((trace != null) && trace.isTraceEnabled()) {
trace.error("Failed (" + e.getClass().getSimpleName() + ")"
+ " to execute " + cmd + ": " + e.getMessage(), e);
}
}
} catch(InterruptedException e) {
if ((trace != null) && trace.isTraceEnabled()) {
trace.warn("Interrupted");
}
Thread.currentThread().interrupt();
break;
}
}
}
});
}
}
// fire-up an update-index command in case index was changed by the constructor
if (!postCacheCommand(new UpdateIndexCommand(backing))) {
if ((trace != null) && trace.isTraceEnabled()) {
trace.warn("Failed to offer update index command to " + cacheDir.getAbsolutePath());
}
}
return backing;
}
public static final boolean postCacheCommand (AsyncCommand cmd) {
return commandsQ.offer(cmd);
}
public static interface AsynchronousFileCacheBackingCreator {
T create (File cacheDir);
}
/**
* Represents an asynchronous command that can be sent to the
* {@link AsynchronousFileCacheBacking} instance to be executed
* on it asynchronously
*/
public static interface AsyncCommand {
/**
* @return The {@link AsynchronousFileCacheBacking} on which
* this command is supposed to be executed
* @see AsynchronousFileCacheBacking#executeCommand(AsyncCommand)
*/
AsynchronousFileCacheBacking getCache ();
}
public static abstract class AbstractCommand implements AsyncCommand {
private final AsynchronousFileCacheBacking cache;
protected AbstractCommand (AsynchronousFileCacheBacking backing) {
if ((cache=backing) == null) {
throw new IllegalStateException("No backing cache specified");
}
}
public final AsynchronousFileCacheBacking getCache () {
return cache;
}
@Override
public String toString() {
return getClass().getSimpleName() + "[" + getCache() + "]";
}
}
public static class ClearCommand extends AbstractCommand {
public ClearCommand (AsynchronousFileCacheBacking cache) {
super(cache);
}
}
public static class UpdateIndexCommand extends AbstractCommand {
public UpdateIndexCommand (AsynchronousFileCacheBacking cache) {
super(cache);
}
}
/**
* Base class for {@link AbstractCommand}s that refer to a cache key
*/
public static abstract class KeyedCommand extends AbstractCommand {
private final String key;
protected KeyedCommand (AsynchronousFileCacheBacking cache, String keyValue) {
super(cache);
if (LangUtil.isEmpty(keyValue)) {
throw new IllegalStateException("No key value");
}
key = keyValue;
}
public final String getKey () {
return key;
}
@Override
public String toString() {
return super.toString() + "[" + getKey() + "]";
}
}
public static class RemoveCommand extends KeyedCommand {
public RemoveCommand (AsynchronousFileCacheBacking cache, String keyValue) {
super(cache, keyValue);
}
}
public static class InsertCommand extends KeyedCommand {
private final byte[] bytes;
public InsertCommand (AsynchronousFileCacheBacking cache, String keyValue, byte[] classBytes) {
super(cache, keyValue);
bytes = classBytes;
}
public final byte[] getClassBytes () {
return bytes;
}
}
}