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EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Configuring


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Elug api package icon.png Key API

Configuring Caching

@Cache

The Cache annotation is used to configure the EclipseLink object cache. By default EclipseLink uses a shared object cache to cache all objects. The caching type and options can be configured on a per class basis to allow optimal caching.

You can define the @Cache annotation on the following:

  • @Entity
  • @MappedSuperclass
  • the root of the inheritance hierarchy (if applicable)

If you define the @Cache annotation on an inheritance subclass, the annotation will be ignored. If you define the @Cache annotation on @Embeddable EclipseLink will throw an exception.

@Cache Annotation Attributes
Attribute Description Default Required?
type Set this attribute to the type (org.eclipse.persistence.annotations.CacheType enumerated type) of the cache that you will be using:
  • FULL
  • WEAK
  • SOFT
  • SOFT_WEAK
  • HARD_WEAK
  • CACHE (not recommended)
  • NONE (not recommended, use shared=false instead)

You can override this attribute with these persistence unit properties:

  • eclipselink.cache.type.<ENTITY>
  • eclipselink.cache.type.default
CacheType.SOFT_WEAK Optional
size Set this attribute to an int value to define the size of cache to use (number of objects) 100
shared Indicate whether cached instances should be in the shared cache or in a client isolated cache (see Isolated Client Session Cache). This allows the shared cache (L2 cache) to be disabled.
  • true - use shared cache for cached instances;
  • false - use client isolated cache for cached instances (no L2 cache).
true Optional
expiry The int value to enable the expiration of the cached instance after a fixed period of time (milliseconds). Queries executed against the cache after this will be forced back to the database for a refreshed copy. -1 (no expiry) Optional
expiryTimeOfDay Specific time of day (org.eclipse.persistence.annotations.TimeOfDay) when the cached instance will expire. Queries executed against the cache after this will be forced back to the database for a refreshed copy. @TimeOfDay(specified=false) Optional
alwaysRefresh Set to a boolean value of true to force all queries that go to the database to always refresh the cache. false Optional
refreshOnlyIfNewer Set to a boolean value of true to force all queries that go to the database to refresh the cache only if the data received from the database by a query is newer than the data in the cache (as determined by the optimistic locking field).

Note: This option only applies if one of the other refreshing options, such as alwaysRefresh, is already enabled.

Note: A version field is necessary to apply this feature.
false Optional
disableHits Set to a boolean value of true to force all queries to bypass the cache for hits, but still resolve against the cache for identity. This forces all queries to hit the database. false Optional
coordinationType Set this attribute to the cache coordination mode (org.eclipse.persistence.annotations.CacheCoordinationType enumerated type). CacheCoordinationType.SEND_OBJECT_CHANGES Optional
@Cache Annotation Example

...
@Entity
@Cache(
  type=CacheType.SOFT, // Cache everything until the JVM decides memory is low.
  size=64000  // Use 64,000 as the initial cache size.
  expiry=36000000,  // 10 minutes
  coordinationType=CacheCoordinationType.INVALIDATE_CHANGED_OBJECTS  // if cache coordination is used, only send invalidation messages.
)
public class Employee {
  ...
}

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Version: 2.4 DRAFT
Other versions...