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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Cache Annotation"
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Revision as of 14:14, 18 February 2011
@Cache Annotation
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.
Attributes of the @Cache Annotation
| Attribute | Description | Default | Required or Optional | Override with Persistence Unit Property |
|---|---|---|---|---|
|
type |
Set this attribute to the type (org.eclipse.persistence.annotations.CacheType enumerated type) of the cache that you will be using:
|
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 |
|
Example of @Cache Annotation
... @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 { ... }
