Package org.aspectj.weaver.tools.cache

Class WeavedClassCache

java.lang.Object

org.aspectj.weaver.tools.cache.WeavedClassCache

public class WeavedClassCache
extends Object

Manages a cache of weaved and generated classes similar to Eclipse Equinox, except designed to operate across multiple restarts of the JVM and with one cache per classloader; allowing URLClassLoaders with the same set of URI paths to share the same cache (with the default configuration).

To enable the default configuration two system properties must be set:

    "-Daj.weaving.cache.enabled=true"
    "-Daj.weaving.cache.dir=/some/directory"
 

The class cache is often something that application developers or containers would like to manage, so there are a few interfaces for overriding the default behavior and performing other management functions.

CacheBacking
Provides an interface for implementing a custom backing store for the cache; The default implementation in DefaultFileCacheBacking provides a naive file-backed cache. An alternate implementation may ignore caching until signaled explicitly by the application, or only cache files for a specific duration. This class delegates the locking and synchronization requirements to the CacheBacking implementation.

CacheKeyResolver
Provides methods for creating keys from classes to be cached and for creating the "scope" of the cache itself for a given classloader and aspect list. The default implementation is provided by DefaultCacheKeyResolver but an alternate implementation may want to associate a cache with a particular application running underneath a container.

This naive cache does not normally invalidate *any* classes; the interfaces above must be used to implement more intelligent behavior. Cache invalidation problems may occur in at least three scenarios:

1. New aspects are added dynamically somewhere in the classloader hierarchy; affecting other classes elsewhere.
2. Use of declare parent in aspects to change the type hierarchy; if the cache has not invalidated the right classes in the type hierarchy aspectj may not be reconstruct the class incorrectly.
3. Similarly to (2), the addition of fields or methods on classes which have already been weaved and cached could have inter-type conflicts.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	CACHE_IMPL
static final String	WEAVED_CLASS_CACHE_ENABLED
static final byte[]	ZERO_BYTES

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	WeavedClassCache(GeneratedClassHandler existingClassHandler, IMessageHandler messageHandler, String name, CacheBacking backing, CacheKeyResolver resolver)

Method Summary

Modifier and Type	Method	Description
void	clear()	Clear the entire cache
static WeavedClassCache	createCache(ClassLoader loader, List<String> aspects, GeneratedClassHandler existingClassHandler, IMessageHandler messageHandler)	Creates a new cache using the resolver and backing returned by the DefaultCacheFactory.
CachedClassReference	createCacheKey(String className, byte[] originalBytes)	Create a key for a normal weaved class
CachedClassReference	createGeneratedCacheKey(String className)	Created a key for a generated class
protected void	error(String message)
protected void	error(String message, Throwable th)
CachedClassEntry	get(CachedClassReference ref, byte[] classBytes)	Get a cache value
static List<WeavedClassCache>	getCaches()	Return a list of all WeavedClassCaches which have been initialized
GeneratedClassHandler	getCachingClassHandler()	Returns a generated class handler which wraps the handler this cache was initialized with; this handler should be used to make sure that generated classes are added to the cache
String	getName()
CacheStatistics	getStats()	Get the statistics associated with this cache, or null if statistics have not been enabled.
void	ignore(CachedClassReference ref, byte[] classBytes)	Put a cache entry to indicate that the class should not be weaved; the original bytes of the class should be used.
protected void	info(String message)
static boolean	isEnabled()	Has caching been enabled through the System property, WEAVED_CLASS_CACHE_ENABLED
void	put(CachedClassReference ref, byte[] classBytes, byte[] weavedBytes)	Put a class in the cache
void	remove(CachedClassReference ref)	Invalidate a cache entry
static void	setDefaultCacheFactory(CacheFactory factory)	The Cache and be extended in two ways, through a specialized CacheKeyResolver and a specialized CacheBacking.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

WEAVED_CLASS_CACHE_ENABLED

public static final String WEAVED_CLASS_CACHE_ENABLED

See Also:

• Constant Field Values

CACHE_IMPL

public static final String CACHE_IMPL

See Also:

• Constant Field Values

ZERO_BYTES

public static final byte[] ZERO_BYTES

Constructor Details

WeavedClassCache

protected WeavedClassCache(GeneratedClassHandler existingClassHandler,
 IMessageHandler messageHandler,
 String name,
 CacheBacking backing,
 CacheKeyResolver resolver)

Method Details

createCache

public static WeavedClassCache createCache(ClassLoader loader,
 List<String> aspects,
 GeneratedClassHandler existingClassHandler,
 IMessageHandler messageHandler)

Creates a new cache using the resolver and backing returned by the DefaultCacheFactory.

Parameters:

loader - classloader for this cache

aspects - list of aspects used by the WeavingAdapter

existingClassHandler - the existing GeneratedClassHandler used by the weaver

messageHandler - the existing messageHandler used by the weaver

Returns:

getName

public String getName()

setDefaultCacheFactory

public static void setDefaultCacheFactory(CacheFactory factory)

The Cache and be extended in two ways, through a specialized CacheKeyResolver and a specialized CacheBacking. The default factory used to create these classes can be set with this method. Since each weaver will create a cache, this method must be called before the weaver is first initialized.

Parameters:

factory -

createGeneratedCacheKey

public CachedClassReference createGeneratedCacheKey(String className)

Created a key for a generated class

Parameters:

className - ClassName, e.g. "com.foo.Bar"

Returns:

the cache key, or null if no caching should be performed

createCacheKey

public CachedClassReference createCacheKey(String className,
 byte[] originalBytes)

Create a key for a normal weaved class

Parameters:

className - ClassName, e.g. "com.foo.Bar"

originalBytes - Original byte array of the class

Returns:

a cache key, or null if no caching should be performed

getCachingClassHandler

public GeneratedClassHandler getCachingClassHandler()

Returns a generated class handler which wraps the handler this cache was initialized with; this handler should be used to make sure that generated classes are added to the cache

isEnabled

public static boolean isEnabled()

Has caching been enabled through the System property, WEAVED_CLASS_CACHE_ENABLED

Returns:

true if caching is enabled

put

public void put(CachedClassReference ref,
 byte[] classBytes,
 byte[] weavedBytes)

Put a class in the cache

Parameters:

ref - reference to the entry, as created through createCacheKey

classBytes - pre-weaving class bytes

weavedBytes - bytes to cache

get

public CachedClassEntry get(CachedClassReference ref,
 byte[] classBytes)

Get a cache value

Parameters:

ref - reference to the cache entry, created through createCacheKey

classBytes - Pre-weaving class bytes - required to ensure that cached aspects refer to an unchanged original class

Returns:

the CacheEntry, or null if no entry exists in the cache

ignore

public void ignore(CachedClassReference ref,
 byte[] classBytes)

Put a cache entry to indicate that the class should not be weaved; the original bytes of the class should be used.

Parameters:

ref - The cache reference

classBytes - The un-weaved class bytes

remove

public void remove(CachedClassReference ref)

Invalidate a cache entry

Parameters:

ref -

clear

public void clear()

Clear the entire cache

getStats

public CacheStatistics getStats()

Get the statistics associated with this cache, or null if statistics have not been enabled.

Returns:

getCaches

public static List<WeavedClassCache> getCaches()

Return a list of all WeavedClassCaches which have been initialized

Returns:

error

protected void error(String message,
 Throwable th)

error

protected void error(String message)

info

protected void info(String message)