Run Ant on Eclipse Mars with Java 1.6

Question

I downloaded the latest release of Eclipse (Mars) and changed the required Java version to 1.6 in eclipse.ini file as my project uses Java 1.6.

I configured installed JREs inside Eclipse to use Java 1.6. But when I try to execute my ant target it creates an error:

JRE version less than 1.7 is not supported.

Is there any workaround to use Java 1.6 in Mars version as I'm unable to upgrade to Java 1.7 at the moment?

Answer 1

I faced the same problem after upgrading to Eclipse Mars.

I solved this by changing the runtime environment of the external tool configuration of the project to JDK7.

I assume you know how to add JDK7 to your installed jre in eclipse

Open External Tools Configurations... and then change the JRE to JDK 1.7

Then change the JRE

But this will create another problem, the compiled jar will be in JDK 7 and this will not work on production servers with JDK6.

To solve this, simply change the target attribute in the task to be 1.6

<javac target="1.6">

As per suggested from @dag and @Chris, Here is updated ant javac task.

Answer 2

We fixed the problem for us using a patched Ant plugin. For Eclipse Neon, also see this link as is noted in the comments on the first page.