MANEH

I did it in a Linux machine( Ubuntu 10.10 ).I am assuming the following programs are already installed in the machine.

Eclipse JAVA IDE

MySQL

DataNucleus is used as an implementation for JDO( Java Data Object ). Follow the link and download

datanucleus-accessplatform-rdbms-<version>.zip from the latest release (and extarct) . I worked with version= 3.1.0-release.

Also download JDO-API from apache. Find the Latest version and download jdo-api-<jdo-version>.jar.

MySQL JDBC driver is also needed. 

Now create a Java Project in Eclipse and add the following jars to the projects CLASSPATH.

From ....../datanucleus-accessplatform-rdbms-<version>/dep/ folder
       asm-<asm-version>.jar
       log4j-<log4j-version>.jar

From ....../datanucleus-accessplatform-rdbms-<version>/lib/ folder
       datanucleus-api-jdo-<version>.jar

       datanucleus-core-<version>.jar

       datanucleus-enhancer-<version>.jar

       datanucleus-rdbms-<version>.jar

....../jdo-api-<jdo-version>.jar

....../mysql-connector-java-<mysql-version>-bin.jar (For MySQL JDBC driver).

Now Export the created Java project to General > AntBuildFiles . Click next and finish nothing much is needed to be done. A build.xml file has been created in the projects root directory. Open it with Eclipse Ide.

Add following snippet of xml to it

<target
 name="-post-compile"
 depends="init" >

 <taskdef
 name="datanucleusenhancer"
 classname="org.datanucleus.enhancer.tools.EnhancerTask"
 classpathref="<ProjectName>.classpath" />

 <echo message="start datanucleusenhancer" />

 <datanucleusenhancer
 classpathref="<ProjectName>.classpath"
 dir="bin"
 verbose="true" >

 <fileset dir="bin" >

 <include name="**/*.class" />
 </fileset>
 </datanucleusenhancer>

 <echo message="end datanucleusenhancer" /> 

</target>  

add this under <project> tag . Change <ProjectName>  according to yours.

Find <javac> tag and add the following line inside <javac></javac> tag.
<compilerarg line=" -processor org.datanucleus.enhancer.EnhancerProcessor" />
Add an attribute verbose="on" to javac tag.

Now find the following xml

<target
 name="build"
 depends="build-subprojects,build-project"/>

Turn it to

<target
 name="build"
 depends="build-subprojects,build-project,-post-compile" />

Now go to project --- properties -- builders and select new. Then select "Ant Builder" . Add a name and in "Buildfile" tab point the build.xml file. Mark only the newly created builder in the "Builders" list.