Unable to find javac compiler while running Ant from Maven2.

If your maven2 pom.xml is using a plugin (maven-antrun-plugin) to run ANT build.xml and a javac task is used in it to compile source then it is very usual to get the following error.

Reason: An Ant BuildException has occured: The following error occurred while executing this line:
C:\maventest\build.xml:79: Unable to find a javac compiler;
com.sun.tools.javac.Main is not on the classpath.
Perhaps JAVA_HOME does not point to the JDK.
It is currently set to ..***\***\jre.

Cause: When Maven2 runs pom.xml it uses the jre (%JAVA_HOME%\jre) instead of %JAVA_HOME% and when ant build is using 'javac' task then maven2 tries to find javac in %JAVA_HOME%\jre.

Solution: Any of the following three can be used. Solution 1 is prefered.

1. Provide a property in pom.xml for maven-antrun-plugin to fork/use javac as an external process. Please see image for reference

2. In pom.xml for maven-compiler-plugin add a property to fork out the javac process.
Read more about the properties of this plugin at http://maven.apache.org/maven-1.x/plugins/java/properties.html

<properties>
<maven.compile.fork>true</maven.compile.fork>
<properties>
 
either under  element or under of  maven-compiler-plugin.
 
3. In ant build.xml at javac task use an attribue fork='true'