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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Configuring"
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* DISABLE_SELECTIVE - enable caching for all entities (@Cacheable can be used to disable caching) | * DISABLE_SELECTIVE - enable caching for all entities (@Cacheable can be used to disable caching) | ||
− | ====JPA 2 persistence.xml cache configuration example==== | + | ======''JPA 2 persistence.xml cache configuration example''====== |
<source lang="xml"> | <source lang="xml"> | ||
<?xml version="1.0" encoding="UTF-8"?> | <?xml version="1.0" encoding="UTF-8"?> |
Revision as of 12:56, 8 May 2012
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Examples
Contents
Configuring Caching
EclipseLink enables a shared (L2) object cache by default on all entity objects. The shared cache can be disabled, or configured through standard JPA 2 configuration or through EclipseLink specific configuration. The EclipseLink cache configuration allows for the configuration of EclipseLink extended cache functionality.
Caching can be configured in EclipseLink through the following mechanisms:
- JPA 2 persistence.xml elements
- JPA 2 @Cacheable annotation and ORM XML element
- EclipseLink @Cache annotation and ORM XML element
- EclipseLink persistence unit properties
JPA 2 persistence.xml Cache Configuration
JPA 2 allows caching to be enabled or disabled through the persistence.xml
element <shared-cache-mode>
. This configures the default caching mode for the entire persistence unit. The default cache mode can be overridden for a specific class using the @Cacheable
annotation.
The valid values for <shared-cache-mode>
are defined in the SharedCacheMode
enum as:
- ALL - enable caching for all entities (overrides any @Cacheable annotation settings)
- NONE - disable caching for all entities (overrides any @Cacheable annotation settings)
- ENABLE_SELECTIVE - disable caching for all entities (@Cacheable can be used to enable caching)
- DISABLE_SELECTIVE - enable caching for all entities (@Cacheable can be used to disable caching)
JPA 2 persistence.xml cache configuration example
<?xml version="1.0" encoding="UTF-8"?> <persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence persistence_2_0.xsd" version="2.0"> <persistence-unit name="acme" transaction-type="RESOURCE_LOCAL"> <provider>org.eclipse.persistence.jpa.PersistenceProvider</provider> <exclude-unlisted-classes>false</exclude-unlisted-classes> <shared-cache-mode>ENABLE_SELECTIVE</shared-cache-mode> </persistence-unit> </persistence>
@Cacheable
@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 { ... }