Stamping the version number and the build time of an application in a properties file so that it could be displayed by an application at runtime seemed like it should be a pretty straightforward task, although it took a bit of time to find a solution that didn’t require the timestamp, version, or ant-run plugins.

I started with a version.txt file at the default package level in src/main/resources of my project, which looks as follows.

version=${pom.version}
build.date=${timestamp}

By default the Maven resources plug-in will not do text substitution (filtering), so it will need to be enabled within the <build> section of the pom.xml file.

<resources>
   <resource>
      <directory>src/main/resources</directory>
      <filtering>true</filtering>
   </resource>
</resources>

Maven does actually define a ${maven.build.timestamp} property which in theory could have been used in the version.txt file, rather than the ${timestamp} property, but unfortunately a bug within Maven prevents the ${maven.build.timestamp} property from getting passed to the resource filtering mechanism. 

(issue:http://jira.codehaus.org/browse/MRESOURCES-99).

The workaround is to create another property within the pom.xml file and set that new property to the timestamp value, in this case, the property name is “timestamp”, which is used above in the version.txt file.  The maven.build.timestamp.format is an optional property for (obviously) defining the timestamp format.

<properties>
   <timestamp>${maven.build.timestamp}</timestamp>
   <maven.build.timestamp.format>yyyy-MM-dd HH:mm</maven.build.timestamp.format>
</properties>

Now, when the build is executed we end up with the version number and build time of the application in the version.txt file. Easy!

version=1.0.2-SNAPSHOT
build.date=2012-03-16 15:42