Question

I have the problem that an specific step in Ant can only be executed when we have Java 1.5 installed in the build computer. The task definition uses uses a jar file that was compiled using 1.5, so running with a 1.4 virtual machine will throw an IncompatibleClassVersion exception.

I have to find a solution meanwhile to have this task working for this specific project that requires 1.4, but a question came to me. How can I avoid defining this task and executing this optional step if I don’t have a specific java version?

I could use the ‘if’ or ‘unless’ tags on the target tag, but those only check if a property is set or not. I also would like to have a solution that doesn’t require extra libraries, but I don’t know if the build-in functionality in standard is enough to perform such a task.

Answer 1

The Java version is exposed via the ant.java.version property. Use a condition to set a property and execute the task only if it is true.

<?xml version='1.0' encoding='UTF-8'?>  <project name='project' default='default'>      <target name='default' depends='javaCheck' if='isJava6'>         <echo message='Hello, World!' />     </target>      <target name='javaCheck'>         <echo message='ant.java.version=${ant.java.version}' />         <condition property='isJava6'>             <equals arg1='${ant.java.version}' arg2='1.6' />         </condition>     </target>  </project>