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


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 or @Cache annotations.

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

The JPA 2 @Cacheable annotation or cacheable XML attribute can be used to selectively enable or disabling caching for a specific entity class.

You can define the @Cacheable annotation on the following:

  • @Entity
  • @MappedSuperclass

If you define the @Cacheable annotation on an entity inheritance subclass, the annotation will be ignored. The @Cacheable annotation is not supported on an @Embeddable.

@Cacheable annotation example
...
@Entity
@Cacheable(false)
public class Employee {
  ...
}

EclipseLink allows entities that are cached to have relationships to entities that are not cached. However, the relationships themselves from cached entities to non-cached entities will not be cached. Entities that are not cached are considered ISOLATED in EclipseLink, entities that are cached are considered SHARED, and cached entities that have relationships to non-cached entities are considered PROTECTED. This can also be configured using the isolation attribute of the EclipseLink @Cache annotation.

@Cache

The @Cache annotation or <cache> XML element can be used to configure caching for a specific entity class.

You can define the @Cache annotation on the following:

  • @Entity
  • @MappedSuperclass

If you define the @Cache annotation on an inheritance subclass, the annotation will be ignored. The @Cache annotation is not supported on an @Embeddable.

@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

There are also types, CACHE and NONE but these are not recommended, and should not be used, to disable caching set isolation=ISOLATED instead.

CacheType.SOFT_WEAK Optional
size Set this attribute to an int value to define the size of cache to use (number of objects) 100 Optional
isolation Set the cache isolation. This allows the shared cache to be enabled or disabled.
  • SHARED - enable shared cache
  • ISOLATED - disable shared cache
  • PROTECTED - enable shared cache and allow relationships to isolated entities
SHARED 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. 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. no expiry 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).
Note: cache coordination must also be configured in the persistence.xml.
CacheCoordinationType.SEND_OBJECT_CHANGES Optional
databaseChangeNotificationType Set this attribute to the database change notification mode (org.eclipse.persistence.annotations.DatabaseChangeNotificationType enumerated type).
Note: database change notification must also be configured in the persistence.xml.
DatabaseChangeNotificationType.INVALIDATE 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 {
  ...
}
Cache XML example
<?xml version="1.0"?>
<entity-mappings
	xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/orm"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://www.eclipse.org/eclipselink/xsds/persistence/orm http://www.eclipse.org/eclipselink/xsds/eclipselink_orm_2_4.xsd"
	version="2.4">
    <entity name="Employee" class="org.acme.Employee" access="FIELD">
        <cache type="SOFT" size="64000" expiry="36000000" coordination-type="INVALIDATE_CHANGED_OBJECTS"/>
    </entity>
</entity-mappings>

EclipseLink Cache Persistence Unit Properties

EclipseLink defines several persistence unit properties that can be used the configure caching defaults, and caching for specific entities.

The caching persistence unit properties include:

  • "eclipselink.cache.shared.default" - enable or disable the shared cache default
  • "eclipselink.cache.shared.<entity-name>" - enable or disable the shared cache for a specific entity
  • "eclipselink.cache.type.default" - set the default cache type
    • Valid values are defined in the CacheType class, "Soft", "Hard", "Weak", "SoftCache", "HardCache", "None".
    • A value of "None" is not recommend and should not be used, use shared=false instead.
  • "eclipselink.cache.type.<entity-name>" - set the cache type for a specific entity
  • "eclipselink.cache.size.default" - set the default cache size
  • "eclipselink.cache.size.<entity-name>" - set the cache size for a specific entity
EclipseLink 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>
        <properties>
            <property name="eclipselink.cache.shared.default" value="false"/>
            <property name="eclipselink.cache.shared.Employee" value="true"/>
            <property name="eclipselink.cache.type.Employee" value="SOFT"/>
            <property name="eclipselink.cache.size.Employee" value="10000"/>
        </properties>
    </persistence-unit>
</persistence>

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Version: 2.4 DRAFT
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