How do I set -Dfile.encoding within ant's build.xml?

If you've got files encoded in a particular way, it's probably best to tell javac that rather than forcing the whole JVM to use a particular encoding. The javac task has an encoding attribute for this reason.

<javac srcdir="${src.dir}" destdir="${build.classes.dir}" encoding="iso-8859-1" />

But really, you should just convert the source files to UTF-8. Everything tastes better in UTF-8. :)

A few options:

1. add -Dfile.encoding=iso-8859-1 to your ANT_OPTS environment variable
2. use <presetdef> to setup defaults for all of your <javac> invocations

Before changing build file i am getting java compile error like below.

ApplicationConstant.java:73: error: unmappable character for encoding ascii public static final String INVALID_MDTVERSION_SECOND = " This not compatible with the server’s Version";

I have encounter this error when I used to have ant java target as:

 <javac encoding="ascii"...>

Than i have change as below

<javac encoding="iso-8859-1" ...> 

This issue got solved.

Ant itself cannot set system properties, but if you really want to, you can write a java program which sets the system property, and execute that from within Ant.