Resolving Ant javac “class file has wrong version” issues

Wed, 03 Jul 2013 15:10:11 +0000

Ever run an ANT build in eclipse and it works just fine, but as soon as you run it outside of eclipse you get something like…

class file has wrong version 51.0, should be 49.0

The issue is likely that you need to “fork” in your javac task…

Before (with error)

javac srcdir="${build.path}" 
 verbose="true" 
 includeantruntime="false" 
 includejavaruntime="false"

After (no error)

javac srcdir="${build.path}" 
 verbose="true" 
 includeantruntime="false" 
 includejavaruntime="false" 
 fork="yes"

Hopefully this can save you about 2 hours some day!

Ant on MarkJacobsen.net