Revision as of 11:52, 23 March 2010

Cache APIs

JPA 2.0 Root | Enhancement Request

Issue Summary

In JPA 2.0 the specification has added a Cache API obtainable from an EntityManagerFactory. This simple API provides developers with rudimentary access and control of a second level cache. User's can interrogate the cache through a contains(Class, Object) API call and cause cached data to be evicted from the cache through an evict(Class, Object), evict(Class) or evictAll() API call.

See The JPA 2.0 Final Release Specification section 7.10 p.306 for details.

General Solution

Should be simple to equate evict to invalidate.

Work Required

1. Develop tests

   approx 1 day

2. Implement API

   approx 2 days

Implementation Details

The Cache API consists of following 4 methods

1. contains(Class cls, Object primaryKey) --- checks whether the class with the specified primary key

   is contained in IdentityMap.

2. evict(Class cls, Object primaryKey) --- invalidates the specified object in the IdentityMap
3. evict(Class cls) --- invalidates the specified class in the IdentityMap.
4. evictAll() --- Invalidates all classes in the IdentityMap.

Refactor 20100322

• The following details describe changes to the original SVN 2896 implementation of Dec 2008 that will arrive in Trunk around April 2010.
• The implementation was modified on the following dates as follows...
  • 20100201: Rev# 6463 - bug# 301063 : Refactor CacheImpl to implement the EclipseLink API interface JpaCache (which implements Cache from JPA 2.0 via the new functions - clear(), clear(Class), clearQueryCache(), clearQueryCache(queryName), timeToLive(Object), isValid(Object), isValid(Class, id), print(), print(Class), printLocks(), validate(), getObject(Class, id), getObject(Object), putObject(Object), removeObject(Class), removeObject(Class, id), containsObject(Object), evictObject(Object), getId(Object)
  • 20100126: Rev# 6406 - bug# 298985 : Refactor Vector usage to Id or CacheId
  • 20091124: Rev# 5875 - bug# 272895 : Check invalidation during contains()
  • 20090513: Rev# 4170 - bug# 275953 : Bootstrap performance and compatibility

Analysis

Issue 1: Fix evict() to handle non-Entity classes

Issue 2: Refactor to get IdentityMapAccessor state through EMF reference

• Doug: "1. Unsure if we need to hold all of this state or just hold the EMF and access

the necessary IdentityMapAccessor through this access."

• We should also get the serverSession from the EMF when required instead of caching it on the CacheImpl.
  • Wherever we see... ServerSession this.serversession
  • replace it with...
  • emf.getServerSession()

Issue 3: Refactor dependencies to use Interfaces instead of Impl subclasses

• Doug: "2. We will need to support more then just ServerSession so we need to have

impls such as this just rely on more general interfaces for the shared session such as Session or DatabaseSession interfaces."

Issue 4: Handle no CMPPolicy case for getId()

• Doug: "3. The createPKVector does not handle the case where the descriptor does not

have a CMPPolicy. This occurs when bootstrapping from native metadata."

• Avoid a possible NPE on the return from descriptor.getCMPolicy()
• createPKVector changed to createPrimaryKeyFromId to refactor out Vector usage in bug 298985

Issue 5: Handle no associated descriptor for Class parameter

• Doug: "3. continued...Also does not properly handle the case where the cls provided is not associated with

a descriptor."

• See contains(Class, Object) and contains(Object)

Issue 6: Add support for @MappedSuperclass descriptors

• Doug: "4. Should we support passing in MappedSuperclass or general types from the

entity inheritance tree? I believe we should."

• MappedSuperclasses do not represent real descriptors - they add functionality to concrete Entities that inherit from them - therefore they should not be evicted.
• As Gordon mentions, we should throw an IllegalArgumentException if a Class (abstract class) representing a MappedSuperclass is passed into evict(Class).

Issue 7: Throw an IAE for Interfaces and Embeddable classes passed to evict()

• Should we throw an IllegalArgumentException for interfaces or embeddables passed into evict(class) as well?

Design

Implementation

Testing

References