Ant script execution fails

I am trying to run Ant script and getting following error at line:

        <javac deprecation="on"
         destdir="${prj.build}"
         debug="${prj.debug}"
         debuglevel="lines,source"
         ***classpathref="compile.classpath">***
         <src path="${prj.src}"/>

Unable to find a javac co开发者_如何转开发mpiler; com.sun.tools.javac.Main is not on the classpath. Perhaps JAVA_HOME does not point to the JDK.

Do you have the JDK installed? The JRE alone is not enough for many ant tasks.

If yes, read the error message: do you have an environment variable named JAVA_HOME, and does it point to the jdk-directory? (This is used by the ant wrapper script to setup the paths right.)