Chapter 12. JDO
We say that error is appearance. This is false. On the contrary,
appearance is always true if we confine ourselves to it. Appearance
is being. —Jean-Paul Sartre,
Truth and Existence
Java Data Objects (JDO) is
one of the first APIs to run through the Java Community Process
(JCP). JDO enables application developers to build applications
without worrying about persistence issues. In other words, it does
for your application the same thing EJB container-managed persistence does for
EJB applications. Where EJB seeks to deliver all the features of
enterprise systems development—such as a distributed component
model and full and distributed transaction management—JDO seeks
to provide developers with a more streamlined set of features.
JDO seeks to give applications with persistence needs the following
capabilities:
Simplicity Database independence Performance
In other words, JDO is a database-independent persistence API that
has a simple programming model designed to support the performance
needs of common applications. Though EJB is database-independent, it
does not have a simple programming model and performs poorly for
small- to medium-scale applications.
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JDO is not a standard part of any Java
platform. You therefore need a host of tools to support JDO
development. Naturally, you need a data store. You also need a JDO
implementation. Depending on the nature of the implementation, you
may need a JDBC driver or any other of a number of third-party
components.
The best way to get started is to download Sun's
reference JDO implementation at
http://java.sun.com/products/jdo.
It uses your filesystem as a data store and frees you from needing
anything else while you are learning JDO.
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