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Instead of writing a giant tutorial that would take days to go through. I have split the

tutorial into three parts that can each be finished in an hour or so. You could finish each

tutorial during a lunch break, so get a sandwich and a beverage, and get started.

EJB 2.0 added a lot of features and functionality, this tutorial focuses on CMP/CMR.

Thus, this tutorial assumes you have a background with EJB, and entity beans. You

don t have to be an EJB expert to follow along. The tutorials cover local interfaces,

deployment descriptor CMP, CMR fields and relationship elements. I will also cover the

full range of relationship types as follows:

One to one

One to many

Many to many

The relationships in the example also cover both unidirectional support and

bidirectional support. The relationships are defined in XML deployment descriptors.

In the first tutorial, you get a taste of CMP/CMR and EJB QL, then I will delve into an

example of a simple EJB 2.0 style CMP entity bean. Part of the example demonstrates

simple EJB QL to create a finder method without a Java implementation. This tutorial is

just to get you acclimated to the terminology and technology. and it adds a teaser

example. The next part, the second tutorial, does the heavy lifting.

In the second tutorial, I will build on the first example to eventually cover each type of

relationship and each type of direction (both unidirectional and bidirectional form). Each

example also has a client that demonstrate accessing the relationships to add, remove

and change related members. Lastly, cascade delete is demonstrated with

consequences for both the one to one relationship example and the one to many

relationship.

In the third tutorial, I will demonstrate advance EJB QL to build finder and select

methods. This tutorial uses the relatioships I built in the last tutorial to show the ends

and outs of EJB QL.

Each example includes source code as follows: Deployment Descriptor,

Implementation class files, Interface class files, Home Interface class files and an Ant

build script. For these examples I will use the J2EE reference implementation which

ships with Cloudscape RDBMS system.

In a future follow on article to these tutorials I will port the final example to IBM

Websphere plus DB2 and JBOSS plus HypersonicSQL to show how the CMP 2.0

entity beans can be deployed to many environments: from light weight single user

databases to industrial strength transaction servers utilizing full scalable behemoth

databases! This article will disucss some of the pitfalls of CMP 2.0 implementation

variants.

Now that I have stated what the tutorial will cover, let s briefly go over what I m not

going to cover. I will not cover (in any detail) support for transactions, as this is not new

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Introducing EJB CMP/CMR, Part 1 of 2