Logo Questions Linux Laravel Mysql Ubuntu Git Menu
 

What is Persistence Context?

People also ask

How does persistence context work?

Persistence Context is an environment or cache where entity instances(which are capable of holding data and thereby having the ability to be persisted in a database) are managed by Entity Manager.It syncs the entity with database. All objects having @Entity annotation are capable of being persisted.

What is persistence context in spring boot?

A persistence context is like a cache which contains a set of persistent entities , So once the transaction is finished, all persistent objects are detached from the EntityManager's persistence context and are no longer managed.

What do we mean by an extended persistence context?

JBoss EJB 3.0 allows you to define long-living EntityManagers that live beyond the scope of a JTA transaction. This is called an Extended Persistence Context. When you specify that an injected EntityManager is an extended persistence context, all object instances remain managed.

How do you inject persistence context?

You can use the @PersistenceContext annotation to inject an EntityManager in an EJB 3.0 client (such as a stateful or stateless session bean, message-driven bean, or servlet). You can use @PersistenceContext attribute unitName to specify a persistence unit by name, as Example 29-13 shows.


A persistence context handles a set of entities which hold data to be persisted in some persistence store (e.g. a database). In particular, the context is aware of the different states an entity can have (e.g. managed, detached) in relation to both the context and the underlying persistence store.

Although Hibernate-related (a JPA provider), I think these links are useful:

http://docs.jboss.org/hibernate/core/4.0/devguide/en-US/html/ch03.html

http://docs.jboss.org/hibernate/entitymanager/3.5/reference/en/html/architecture.html

In Java EE, a persistence context is normally accessed via an EntityManager.

http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html

The various states an entity can have and the transitions between these are described below:

http://docs.jboss.org/hibernate/entitymanager/3.6/reference/en/html/objectstate.html

https://vladmihalcea.com/wp-content/uploads/2014/07/jpaentitystates.png


  1. Entities are managed by javax.persistence.EntityManager instance using persistence context.
  2. Each EntityManager instance is associated with a persistence context.
  3. Within the persistence context, the entity instances and their lifecycle are managed.
  4. Persistence context defines a scope under which particular entity instances are created, persisted, and removed.
  5. A persistence context is like a cache which contains a set of persistent entities , So once the transaction is finished, all persistent objects are detached from the EntityManager's persistence context and are no longer managed.

Taken from this page:

Here's a quick cheat sheet of the JPA world:

  • A Cache is a copy of data, copy meaning pulled from but living outside the database.
  • Flushing a Cache is the act of putting modified data back into the database.
  • A PersistenceContext is essentially a Cache. It also tends to have it's own non-shared database connection.
  • An EntityManager represents a PersistenceContext (and therefore a Cache)
  • An EntityManagerFactory creates an EntityManager (and therefore a PersistenceContext/Cache)

A persistent context represents the entities which hold data and are qualified to be persisted in some persistent storage like a database. Once we commit a transaction under a session which has these entities attached with, Hibernate flushes the persistent context and changes(insert/save, update or delete) on them are persisted in the persistent storage.


Both the org.hibernate.Session API and javax.persistence.EntityManager API represent a context for dealing with persistent data.

This concept is called a persistence context. Persistent data has a state in relation to both a persistence context and the underlying database.