Java Persistence APIs: Employee Registry Example (Enterprise JavaBeans 3.1)

Description

Enterprise applications frequently need to deal with state which survives application restarts. We call this “persistent state,” and it’s typically modeled by a program called a relational database management system (RDBMS). Handling the transformation/ mapping between the row-based RDBMS and Java objects is a rote process for application developers, so we offload this responsibility to the Java Persistence API (JPA). In this fashion we’re free to interact with regular getters/setters on Java objects while the mechanics of getting data into and out of the backing database is handled for us.

EJB integrates with JPA via the entity bean through 14 detail the APIs needed to properly model, map, persist, and retrieve data with a real database. Our example is an employee registry, where we apply a variety of techniques to draw relationships between mapped types and query the DB efficiently.

Source Listing

Following is a full listing of all source code used in this runnable example.

Implementation Resources

SimpleEmployee.java

EmbeddedEmployeePK.java

EmployeeType.java

EmployeeWithEmbeddedPK.java

EmployeeWithExternalCompositePK.java

EmployeeWithMappedSuperClassId.java

EmployeeWithProperties.java

ExternalEmployeePK.java

Address.java

Computer.java

Customer.java

Employee.java

Phone.java

PhoneType.java

Task.java

Team.java

Customer.java

Employee.java

Person.java

Customer.java

Employee.java

Person.java

Customer.java

Employee.java

Person.java

EntityListenerEmployee.java

EventTracker.java

persistence.xml

Test Resources

EmployeeIntegrationTest.java