Cookbook: How To Add Build Time To A JAR Manifest?

Summary

This recipe describes how to add build time to a JAR manifest by calling Apache Ant tasks.

Prerequisite Plugins

Here is the list of the plugins used:

Plugin Version
antrun 1.1
jar 2.2

Sample Generated Manifest

Manifest-Version: 1.0
Archiver-Version: Plexus Archiver
Created-By: Apache Maven
Built-By: vsiveton
Build-Jdk: 1.5.0_12
Build-Time: 2008-01-18 06:53:13

Recipe

Configuring MANIFEST.MF

To generate and add build time into a Jar Manifest, we are using MANIFEST.MF, located in the src/main/resources/META-INF directory, which contains a built time value to be interpolated, i.e.

Build-Time: ${build.time}

Configuring The POM

The value ${build.time} from the MANIFEST.MF will be filtering by Maven due to the <filtering> element. The value is taken from the file ${basedir}/target/filter.properties, listed by the <filter> element, i.e.

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

    <filters>
      <filter>${basedir}/target/filter.properties</filter>
    </filters>

Configuring Maven Antrun Plugin

The filter.properties file will be generated by the Antrun plugin. We use two core Ant Tasks, <tstamp> and <echo>.

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-antrun-plugin</artifactId>
        <executions>
          <execution>
            <phase>generate-resources</phase>
            <goals>
              <goal>run</goal>
            </goals>
            <configuration>
              <tasks>
                <!-- Safety -->
                <mkdir dir="${project.build.directory}"/>

                <tstamp>
                  <format property="last.updated" pattern="yyyy-MM-dd hh:mm:ss"/>
                </tstamp>
                <echo file="${basedir}/target/filter.properties" message="build.time=${last.updated}"/>
              </tasks>
            </configuration>
          </execution>
        </executions>
      </plugin>

Configuring Maven Jar Plugin

The last configuration is to set the defaultManifestFile to true to enable it.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-jar-plugin</artifactId>
  <configuration>
    <useDefaultManifestFile>true</useDefaultManifestFile>
  </configuration>
</plugin>

Running Maven

Just call Maven to generate the package:

mvn package

Other Tips

You could tweak the Jar Plugin configuration into the War Plugin.

Resources