Overview

This is the source code for the article "Simplifying Domain Model Persistence in a J2EE application by using JDO" that was published on www.theserverside.com in February 2003.

It illustrates how to use Java Data Objects (JDO) to implement a domain model in a J2EE application. Specifically, it shows how to use JDO in a way that improves testability by decoupling the domain model code from the application server and the database. It facilitates three types of development and testing:

• Outside of the application server and without a database - this is the fastest way to develop and test since you are not slowed down by having to keep the database schema in sync or by having to redeploy
• Outside of the application server but with a database - tests the O/R mapping but without having to redeploy
• Inside the application server - requires deployment

This software is licensed under the BSD License.

A link to the article can be found here.

The source code consists of a self contained ANT-based project workspace. The organization of the workspace is described here.

The software you need to build the application are described here.

The instructions for building and running the application are described here.

Things to remember

• This example code is still work in progress. In particular, it is subset of the files of a more elaborate application, that features pluggable persistence and state management.
• In the near future this example will be expanded to include more test cases and a presentation tier.

Application

The design of the example application is shown in the following diagram:

It consists of the following components:

• A JDO implementation of the domain model
• A session facade that invokes the domain model
• A JUnit-based test case that invokes the session facade
• A servlet that initializes the system on startup