Build and Version Numbering for Java Projects (ant, cvs, hudson)

For several of my projects I capture the subversion revision number, time, user who ran the build, and some system information, stuff them into a .properties file that gets included in the application jar, and read that jar at runtime.

The ant code looks like this:

<!-- software revision number -->
<property name="version" value="1.23"/>

<target name="buildinfo">
    <tstamp>
        <format property="builtat" pattern="MM/dd/yyyy hh:mm aa" timezone="America/New_York"/>
    </tstamp>        
    <exec executable="svnversion" outputproperty="svnversion"/>
    <exec executable="whoami" outputproperty="whoami"/>
    <exec executable="uname" outputproperty="buildsystem"><arg value="-a"/></exec>

    <propertyfile file="path/to/project.properties"
        comment="This file is automatically generated - DO NOT EDIT">        
        <entry key="buildtime" value="${builtat}"/>
        <entry key="build" value="${svnversion}"/>
        <entry key="builder" value="${whoami}"/>
        <entry key="version" value="${version}"/>
        <entry key="system" value="${buildsystem}"/>
    </propertyfile>
</target>

It's simple to extend this to include whatever information you might want to add.

Your build.xml

...
<property name="version" value="1.0"/>
...
<target name="jar" depends="compile">
    <buildnumber file="build.num"/>
    <manifest file="MANIFEST.MF">
        ...
        <attribute name="Main-Class" value="MyClass"/>
        <attribute name="Implementation-Version" value="${version}.${build.number}"/>
        ...
    </manifest>
</target>
...

Your java code

String ver = MyClass.class.getPackage().getImplementationVersion();