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EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Configuring
< EclipseLink | UserGuide | JPA | Basic JPA Development | Caching
Revision as of 10:03, 8 May 2012 by Unnamed Poltroon (Talk)
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Examples
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.
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:
You can override this attribute with these persistence unit properties:
|
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 | 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 { ... }