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Core Java™ Data Objects by Heiko Bobzin, Michael Vorburger, Keiron McCammon, Sameer Tyagi

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9.4. Entity Beans and JDO

Having discussed session and message-driven enterprise beans above, let's now turn to another type of enterprise bean, entity beans. As per the EJB specification[4] , an entity enterprise bean has the following characteristics:

[4] http://java.sun.com/products/ejb/

  • Provides an object view of data in the database.

  • Allows shared access from multiple users.

  • Can be long-lived (lives as long as the data in the database).

Two different types of entity beans exist: container-managed persistence (CMP) and bean-managed persistence (BMP) entity beans. Both types of entity beans can be created and removed, and queried with a language named EJBQL. They also have an identity, their primary key. Does this all seem remarkably similar ...

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