Chapter 8: Using JDO to Learn More

Overview

The JDO learning tools are a small but comprehensive set of programs that you can use for several purposes. You can use them as an introduction to JDO. You can use them to verify what you have learned about JDO. Most importantly, you can use them to learn more. The first five JDO Learning Tools are discussed in this chapter.

• TestJDOHelper

• TestFactory

• MegaCups

• Library

• StateTracker

The five learning programs are not examples of how your application might use JDO. Instead, they are atypical applications whose purpose is to illuminate the interactions with JDO. TestJDOHelper and TestFactory allow you to start using a JDO implementation and find out more about its capabilities. The MegaCups program demonstrates JDO's ability to handle multiple, concurrent updates. The Library program allows you to interactively populate a small town's library and run your own queries against its objects. Using it, you can test JDO's query language. The StateTracker program allows you to manipulate and view the managed and unmanaged state of persistent, transactional, and unmanaged apples. You can use it to execute all of JDO's explicit operations and many of its implicit operations, and you can see the consequences on managed objects.

In addition to the five learning programs, there are two sets of example programs, the rental application and the quote server, that are discussed in Chapters 9 through 11. The rental applications and the quote servers provide examples of how your application might use JDO. Between them, they cover many application architectures. The rental application is a prototype reservation system for a fictitious lighthouse rental company. It comes in three versions: the rental Swing application, the rental Web application, and the rental enterprise (EJB) application. Each version implements nearly the same set of requirements. Each chapter from 9 to 11 takes one version of the rental application as its main topic. The quote server application stores new quotes given to it and serves up a random quote upon demand. It is implemented in five types of Enterprise JavaBeans: a stateless CMT session bean, a stateful CMT session bean, a stateless BMT session bean, a stateful BMT session bean, and a BMP entity bean. The quote server examples are discussed in Chapter 6 as well as Chapter 11.

The JDO Learning Tools 1.0 are copyright by Yankee Software and are provided to the community of Java programmers under the open source GNU General Public License. Instructions for downloading the JDO Learning Tools are found in the section "Step One: Download Open Source JDO Learning Tools" that follows in this chapter. You are encouraged to contribute improvements to make future releases of the JDO Learning Tools better for all of us.