com.ibm.websphere.objectgrid.jpa
Class JPAEntityLoader

java.lang.Object
  com.ibm.websphere.objectgrid.jpa.JPALoader
      com.ibm.websphere.objectgrid.jpa.JPAEntityLoader

All Implemented Interfaces:

Loader, RetryableLoader

public class JPAEntityLoader
extends JPALoader

This is the entity loader that uses Java Persistence API (JPA) to load and store data in the "database". Therefore, a JPA provider is required to use this feature. The "database" here can be any backend supported by the chosen JPA provider.

A TransactionCallback plugin, JPATxCallback, should be configured on the ObjectGrid to provide the transaction coordination between the ObjectGrid transaction and the JPA entity manager transaction for this loader to work.

A JPA persistence unit name and entity class name are required to use JPA. The persistence unit name is provided to the JPATxCallback instance and the entity class name is provided to this loader. This establishes a one to one relation between ObjectGrid instances and JPA persistence units and a one to one relation between ObjectGrid maps and JPA entities.

When defining the ObjectGrid entity metadata for the entity map, an ObjectGrid entity class has already been defined. If the JPA entity class is the same as this ObjectGrid entity class, there is no need to provide the entity class any more. If the JPA entity class is different, it is required to be set using the attribute "entityClassName".

This loader is used for ObjectGrid entity maps only. Use JPALoader for ObjectGrid maps that store POJOs.

If entities have relationships to other entities, each entity map must have an independent JPAEntityLoader. The JPAEntityLoader cannot be used to load the root entity and its children.

If the preloadPartition property is set to a valid partition, the preloadMap method will preload all the data into the ObjectGrid maps from that partition. The preloadMap uses ClientLoader to preload a map. By default, the preloadPartition is set to -1 to disable the map preload.

This JPAEntityLoader implements the RetryableLoader because it can handle a retry record from ObjectGrid. When the retry indication slot contains a Boolean.TRUE, the JPAEntityLoader handles the ObjectGrid log elements in the following ways:

1. For an insert or update type log element, it calls EntityManager.merge(Object) method to merge the entity.
2. For a delete type log element, if calls EntityManager.find(Class, Object) method to find the entity. If the entity is found, it calls EntityManager.remove(Object) method to remove it.

Since:

WAS XD 6.1.0.3

See Also:

ClientLoader

Nested Class Summary

Nested classes/interfaces inherited from interface com.ibm.websphere.objectgrid.plugins.Loader

Loader.SpecialValue

Field Summary

Fields inherited from class com.ibm.websphere.objectgrid.jpa.JPALoader

entityClass, entityClassName, mapName, ogName, preloadPartition, retryIndicationSlot, txCallback

Fields inherited from interface com.ibm.websphere.objectgrid.plugins.Loader

KEY_NOT_FOUND

Constructor Summary

JPAEntityLoader()

Method Summary

void	batchUpdate(TxID txid, LogSequence sequence) Write the data from ObjectGrid entity maps to JPA.
List	get(TxID tx, List keys, boolean forUpdate) Returns the list of values corresponding to the set of keys passed in by retrieving the data using JPA.
protected void	initialize(ObjectGrid grid, BackingMap bmap)

Methods inherited from class com.ibm.websphere.objectgrid.jpa.JPALoader

getEntityClassName, getPreloadPartition, getTxCallback, preloadMap, setEntityClassName, setPreloadPartition, setRetryIndicationSlot

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

JPAEntityLoader

public JPAEntityLoader()

Method Detail

batchUpdate

public void batchUpdate(TxID txid,
                        LogSequence sequence)
                 throws LoaderException,
                        OptimisticCollisionException

Write the data from ObjectGrid entity maps to JPA.

The LogSequence contains a sequence of log elements which contain entity key and value tuples. These tuples are converted in to JPA POJO entities, which are then used to interact with JPA to insert, update, or remove the JPA entities.

Specified by:

batchUpdate in interface Loader

Overrides:

batchUpdate in class JPALoader

Parameters:

txid - the transaction id object

sequence - the set of changes being applied to this object's map

Throws:

LoaderException - if an error occurs during processing of this method

OptimisticCollisionException - if a version mismatch is detected

See Also:

Loader.batchUpdate(TxID, LogSequence)

get

public List get(TxID tx,
                List keys,
                boolean forUpdate)
         throws LoaderException

Returns the list of values corresponding to the set of keys passed in by retrieving the data using JPA.

The data retrieved from JPA are POJO entities, which are then converted into ObjectGrid entity tuples. Each key provided will have a corresponding entity tuple in the returned list.

Specified by:

get in interface Loader

Overrides:

get in class JPALoader

Parameters:

tx - the transaction ID object

keys - List of keys

forUpdate - true when a getForUpdate method is called. This parameter can be used to do a "SELECT for UPDATE" invocation for proper database locking. JPA as a result of JPA find operation.

Returns:

List of Object values

Throws:

LoaderException - if an error occurs during processing of this method

See Also:

Loader.get(TxID, List, boolean)

initialize

protected void initialize(ObjectGrid grid,
                          BackingMap bmap)
                   throws LoaderException

Throws:

LoaderException