org.eclipse.persistence.sessions.interceptors.CacheInterceptor Maven / Gradle / Ivy
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/*
* Copyright (c) 1998, 2018 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0,
* or the Eclipse Distribution License v. 1.0 which is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
*/
// Contributors:
// Gordon Yorke - Initial Feature development
// 12/14/2017-3.0 Tomas Kraus
// - 522635: ConcurrentModificationException when triggering lazy load from conforming query
package org.eclipse.persistence.sessions.interceptors;
import java.util.Collection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.exceptions.QueryException;
import org.eclipse.persistence.indirection.ValueHolderInterface;
import org.eclipse.persistence.internal.helper.Helper;
import org.eclipse.persistence.internal.identitymaps.CacheKey;
import org.eclipse.persistence.internal.identitymaps.IdentityMap;
import org.eclipse.persistence.internal.sessions.AbstractSession;
import org.eclipse.persistence.mappings.ForeignReferenceMapping;
/**
*
* Purpose: Define a class through which Cache access can be
* intercepted.
*
* Description: EclipseLink makes extensive use of caching
* functionality. This class provides the mechanism for intercepting the cache
* access. Once intercepted applications can allow the process to continue by
* calling the method on the class attribute targetIdentityMap as described in
* the API javadocs or redirect the process entirely. * As with IdentityMaps an
* entire class inheritance hierarchy will share the same interceptor.
*
* To implement a CacheInterceptor users should subclass this class implementing
* those methods they wish to intercept.
*
* Configuration: Interceptors may be added to a session by using a
* Session or Descriptor customizer to set the class name of the interceptor on
* the target ClassDescriptor through the method
* setCacheInterceptorClass(Class).
*/
public abstract class CacheInterceptor implements IdentityMap {
/**
* This attribute stores the actual IdentityMap as configured by the user.
*/
protected IdentityMap targetIdentityMap;
protected AbstractSession interceptedSession;
public CacheInterceptor(IdentityMap targetIdentityMap, AbstractSession interceptedSession){
this.targetIdentityMap = targetIdentityMap;
this.interceptedSession = interceptedSession;
}
/**
* Acquire a deferred lock on the object.
* This is used while reading if the object has relationships without indirection.
* This first thread will get an active lock.
* Other threads will get deferred locks, all threads will wait until all other threads are complete before releasing their locks.
*/
public CacheKey acquireDeferredLock(Object primaryKey, boolean isCacheCheckComplete){
return createCacheKeyInterceptor(this.targetIdentityMap.acquireDeferredLock(primaryKey, isCacheCheckComplete));
}
/**
* Acquire an active lock on the object.
* This is used by reading (when using indirection or no relationships) and by merge.
*/
public CacheKey acquireLock(Object primaryKey, boolean forMerge, boolean isCacheCheckComplete){
return createCacheKeyInterceptor(this.targetIdentityMap.acquireLock(primaryKey, forMerge, isCacheCheckComplete));
}
/**
* Acquire an active lock on the object, if not already locked.
* This is used by merge for missing existing objects.
*/
public CacheKey acquireLockNoWait(Object primaryKey, boolean forMerge){
CacheKey cacheKeyToBeWrapped = this.targetIdentityMap.acquireLockNoWait(primaryKey, forMerge);
if (cacheKeyToBeWrapped != null){
return createCacheKeyInterceptor(cacheKeyToBeWrapped);
}
return null;
}
/**
* Acquire an active lock on the object, if not already locked.
* This is used by merge for missing existing objects.
*/
public CacheKey acquireLockWithWait(Object primaryKey, boolean forMerge, int wait) {
CacheKey cacheKeyToBeWrapped = this.targetIdentityMap.acquireLockWithWait(primaryKey, forMerge, wait);
if (cacheKeyToBeWrapped != null) {
return createCacheKeyInterceptor(cacheKeyToBeWrapped);
}
return null;
}
/**
* Acquire a read lock on the object.
* This is used by UnitOfWork cloning.
* This will allow multiple users to read the same object but prevent writes to the object while the read lock is held.
*/
public CacheKey acquireReadLockOnCacheKey(Object primaryKey) {
return createCacheKeyInterceptor(this.targetIdentityMap.acquireReadLockOnCacheKey(primaryKey));
}
/**
* Acquire a read lock on the object, if not already locked.
* This is used by UnitOfWork cloning.
* This will allow multiple users to read the same object but prevent writes to the object while the read lock is held.
*/
public CacheKey acquireReadLockOnCacheKeyNoWait(Object primaryKey) {
CacheKey cacheKeyToBeWrapped = this.targetIdentityMap.acquireReadLockOnCacheKeyNoWait(primaryKey);
if (cacheKeyToBeWrapped != null){
return createCacheKeyInterceptor(cacheKeyToBeWrapped);
}
return null;
}
/**
* Add all locked CacheKeys to the map grouped by thread.
* Used to print all the locks in the identity map.
*/
public void collectLocks(HashMap threadList) {
this.targetIdentityMap.collectLocks(threadList);
}
/**
* Clone the map and all of the CacheKeys.
* This is used by UnitOfWork commitAndResumeOnFailure to avoid corrupting the cache during a failed commit.
*/
public abstract Object clone();
/**
* Return true if an CacheKey with the primary key is in the map.
* User API.
* @param primaryKey is the primary key for the object to search for.
*/
public boolean containsKey(Object primaryKey) {
return this.targetIdentityMap.containsKey(primaryKey);
}
protected abstract CacheKeyInterceptor createCacheKeyInterceptor(CacheKey wrappedCacheKey);
/**
* Allow for the cache to be iterated on. This method is only used during debugging when
* validateCache() has been called to print out the contents of the cache.
*/
public Enumeration elements() {
return this.targetIdentityMap.elements();
}
/**
* Return the object cached in the identity map or null if it could not be found.
* User API.
*/
public Object get(Object primaryKey){
return this.targetIdentityMap.get(primaryKey);
}
/**
* ADVANCED:
* Using a list of Entity PK this method will attempt to bulk load the entire list from the cache.
* In certain circumstances this can have large performance improvements over loading each item individually.
* @param pkList List of Entity PKs to extract from the cache
* @param descriptor Descriptor type to be retrieved.
* @return Map of Entity PKs associated to the Entities that were retrieved
* @throws QueryException
*/
public abstract Map