LOTD #22: How to inject JPA resources ? - PersistenceUnit vs PersistenceContext
Java Persistence API defines a standard object/relational mapping using
POJOs. In JPA, a persistence
unit is described using "persistence.xml", bundled with
the web application, injected into your web application and then POJOs
are used to access all the information from the underlying persistence
mechanism such as a database.
JPA can injected into your application couple of different ways as
Which one is preferred, why, and pros/cons are very clearly explained
in (slightly old but very relevant) href="http://weblogs.java.net/blog/ss141213/archive/2005/12/dont_use_persis_1.html">this
blog. It also discusses a JNDI approach.
In case you are interested in the summary:
- Use "@PersistenceUnit EntityManagerFactory" for Servlets
because of thread safety
- Use "@PersistenceContext EntityManager" in EJBs for
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