About EntityManager

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Manual
21

CRUD Database Operations with JPA [2011-02-11]

Given an EntityManager, em, that represents a JPA connection to the object database, we can use ... an ordinary Java object. It then becomes associated with an EntityManager and with its transaction (as ... can become productive very quickly. The EntityManager object serves as the factory for Query instances
Manual
21

Shared (L2) Entity Cache [2011-09-20]

Every EntityManager owns a persistence context, which is a collection of all the entity objects ... an entity object that is already managed by the EntityManager returns the existing instance from ... is one EntityManager. This section describes a level 2  (L2) cache of entity objects, which is managed
Manual
21

CRUD Database Operations with JPA

Given an EntityManager, em, that represents a JPA connection to the object database, we can use ... an ordinary Java object. It then becomes associated with an EntityManager and with its transaction (as ... can become productive very quickly. The EntityManager object serves as the factory for Query instances
Manual
21

Shared (L2) Entity Cache

Every EntityManager owns a persistence context, which is a collection of all the entity objects ... an entity object that is already managed by the EntityManager returns the existing instance from ... is one EntityManager. This section describes a level 2  (L2) cache of entity objects, which is managed
Manual
21

Shared (L2) Entity Cache [2019-08-09]

Every EntityManager owns a persistence context, which is a collection of all the entity objects ... an entity object that is already managed by the EntityManager returns the existing instance from ... is one EntityManager. This section describes a level 2  (L2) cache of entity objects, which is managed
Manual
20

Retrieving JPA Entity Objects

. Given an EntityManager em, the following code fragment demonstrates retrieval of an Employee object ... if the specified class is not an entity class. If the EntityManager already manages the specified entity ... except that if the entity object is not already managed by the EntityManager a hollow object
Manual
17

DELETE Queries in JPA/JPQL

the entity objects into an EntityManager. Removing these objects from the EntityManager within an active ... them, but it should be used cautiously because bypassing the EntityManager may break its synchronization with the database. For example, the EntityManager may not be aware that a cached entity object in its persistence
Manual
16

UPDATE SET Queries in JPA/JPQL [2011-11-22]

objects into an EntityManager. Updating the relevant entity object fields within an active transaction ... them, but it should be used cautiously because bypassing the EntityManager may break its synchronization with the database. For example, the EntityManager may not be aware that a cached entity object in
Manual
16

Locking in JPA [2011-04-30]

another EntityManager) since it was retrieved by the current updater. Optimistic locking ... another EntityManager instance) currently holds a PESSIMISTIC_WRITE lock on that database object. A PESSIMISTIC ... .lock(e1, lockMode1); em2.lock(e2, lockMode2); em1 and em2 are two EntityManager instances
Manual
16

UPDATE SET Queries in JPA/JPQL

objects into an EntityManager. Updating the relevant entity object fields within an active transaction ... them, but it should be used cautiously because bypassing the EntityManager may break its synchronization with the database. For example, the EntityManager may not be aware that a cached entity object in