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Method javax.persistence.EntityManager void joinTransaction() Indicate to the entity manager that a JTA transaction is active. This method should be called on a JTA application managed entity manager that was created outside the scope of the active transaction to associate it with the current JTA


Method javax.persistence.EntityManager boolean isOpen() Determine whether the entity manager is open. Returns: true until the entity manager has been closed Since: JPA 1.0

lock(entity, lockMode)

Method javax.persistence.EntityManager void lock( Object entity, LockModeType lockMode ) Lock an entity instance that is contained in the persistence context with the specified lock mode type. If a pessimistic lock mode type is specified and the entity contains a version attribute, the persistence

Obtaining a JPA Database Connection

In JPA a database connection is represented by the EntityManager interface. Therefore, in order to manipulate an ObjectDB database we need an EntityManager instance. Operations that modify database ... an EntityManager instance consists of two steps. First we need to obtain an instance

Working with JPA Entity Objects

this state the object is not yet associated with an EntityManager and has no representation in ... via an EntityManager’s persist method, which must be invoked within an active transaction. On transaction commit, the owning EntityManager stores the new entity object to the database. More details on storing objects

Database Connection using JPA

A connection to a database is represented by an EntityManager instance, which also provides ... database connection, using a separate EntityManager instance, for every HTTP request. The main role of an EntityManagerFactory instance is to support instantiation of EntityManager instances

Setting and Tuning of JPA Queries

on which they were invoked). Flush Mode (setFlushMode) Changes made to a database using an EntityManager ... of other EntityManager instances). JPA implementations can easily make uncommitted changes visible in ... the application, either at the EntityManager level as a default for all the queries in that EntityManager

Detached Entity Objects

EntityManager but still represent objects in the database. Compared to managed entity objects, detached ... the database unless modified detached objects are merged back into an EntityManager to become managed again. Detached objects are useful in situations in which an EntityManager is not available

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

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

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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