build.xml

<?xml version="1.0"?>
<project name="Widgetset compile" basedir="." default="compile-widgetset">
    <target name="compile-widgetset">
        <path id="classpath">
            <pathelement path="grails-app/vaadin"/>
            <pathelement path="src/java"/>
            <pathelement path="target/classes"/>
            <fileset dir="libs-widgetset">
                <include name="*.jar"/>
            </fileset>
        </path>
        <echo>Compiling ${widgetset}...</echo>
        <property name="module" value="app.AppWidgetSet" />
        <property name="module.output.dir" location="web-app/VAADIN/widgetsets" />
        <property name="localWorkers" value="2" />
        <mkdir dir="${module.output.dir}" />
        <java classname="com.google.gwt.dev.Compiler" classpathref="classpath" failonerror="yes" fork="yes" maxmemory="512m">
            <arg value="-war" />
            <arg value="${module.output.dir}" />
            <arg value="-localWorkers" />
            <arg value="${localWorkers}" />
            <arg value="-strict" />
            <arg value="${module}" />
            <sysproperty key="vFailIfNotSerializable" value="true" />
            <jvmarg value="-Xss8M" />
            <jvmarg value="-XX:MaxPermSize=256M" />
            <jvmarg value="-Djava.awt.headless=true" />
        </java>
    </target>
</project>