Generating EJB 3 Persistent Objects

EJB 3.0 is the latest revision of the Enterprise Java Beans specification. One of the principal goals of EJB 3.0 is: "Simplification of object persistence by the definition of a light-weight object/relational mapping facility based on the direct use of Java classes rather than persistent components."

One of the most significant changes in EJB 3.0 is the introduction of a standard O/R mapping specification and the move to POJO based persistence.

EJB 3.0 persistence provides a lightweight persistence solution for Java applications. It supports powerful, high performance and transparent object/relational persistence, which can be used both in container and out of container.

EJB 3.0 persistence lets you develop persistent objects using POJO (Plain Old Java Object). All the common Java idioms, including association, inheritance, polymorphism, composition, and the Java collections framework are supported. EJB 3.0 persistence allows you to express queries in its own portable SQL extension (EJBQL), as well as in native SQL.

PowerDesigner supports the design of Java classes, database schema and Object/Relational mapping (O/R mapping). Using these metadata, PowerDesigner can generate codes for EJB 3 persistence, including:

• Generating Entities for EJB 3.0
  You generate entities for EJB 3.0 as follows:
• Adding EJB 3 Persistence Support
  PowerDesigner uses an EJB 3.0 Extended Model Definition to generate EJB 3.0 persistence artifacts.
• Defining EJB 3 Basic O/R Mapping
  There are three kinds of persistent classes in EJB 3:
• Defining EJB 3 Association Mappings
  EJB 3 persistence provides support for most of the association mapping strategies. We will just address the differences here.
• Defining EJB 3 Inheritance Mappings
  EJB 3 persistence supports all three popular inheritance mapping strategies and also mixed strategies.
• Defining EJB 3 Persistence Default Options
  The following default persistent options can be set at the model, package or class level:
• Defining EJB 3 Persistence Configuration
  There are some persistence properties which are used for database connection. You need to set them before run the generated application.
• Checking the Model
  To keep the model and mappings correct and consistent, you need to run a model check. If there are errors, you need to fix them. You can also run model checking before code generation.
• Generating Code for EJB 3 Persistence
  In order to generate code for EJB 3 persistence, you must.