20 Using Database Events to Invalidate the Cache

This chapter describes EclipseLink Database Change Notification (DCN), which allows you to use caching with a shared database in JPA.

This chapter includes the following sections:

• Introduction to the Solution

• Implementing the Solution

• Limitations on the Solution

• Additional Resources

Use Case

Users want to use a shared cache with their JPA application, however, external applications update the same database data, or the cache is in a clustered environment. The cache may retain stale data.

Solution

EclipseLink provides an API which allows the database to notify EclipseLink of database changes. The changed objects can then be invalidated in the EclipseLink shared cache. Stale data can be discarded, even if other applications access the same data in the database.

Components

• Oracle 11gR2 (11.2) (or higher) database

• EclipseLink 2.4 or later.

  • EclipseLink library: eclipselink.jar

  • JDBC library: ojdbc6.jar.

  • JPA library: persistence.jar.

Sample

For sample files that illustrate the use of Database Change Notification and shared caching in an application that uses JPA, see "EclipseLink/Examples/JPA/DCN" in the EclipseLink documentation.

http://wiki.eclipse.org/EclipseLink/Examples/JPA/DCN