JAVA_HOME gets mangled by Maven - maven-2

Question

I'm retrofitting bunch of existing Java projects with unified Maven build. Since each project is mature and has established Ant based build all I'm using maven-antrun-plugin to execute existing build.xml as follows:
<plugin>
<artifactId>maven-antrun-plugin</artifactId>
<executions>
<execution>
<phase>compile</phase>
<configuration>
<tasks>
<ant antfile="build.xml" target="compile" />
</tasks>
</configuration>
<goals>
<goal>run</goal>
</goals>
</execution>
</executions>
</plugin>
When I run mvn compile build fails with this message:
[INFO] An Ant BuildException has occured: The following error occurred
while executing this line:
build.xml:175: 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 "C:\Java\jdk1.6.0_13\jre"
What puzzles me is
I have JAVA_HOME=C:\Java\jdk1.6.0_13 as part of my environment setup and when mvn.bat is executed that is exactly value I'm getting, however as you see in the error message it comes up as C:\Java\jdk1.6.0_13\jre
If I run ant compile everything compiles just fine
Does it mean that perhaps maven-antrun-plugin does something like set JAVA_HOME=%JAVA_HOME%\jre? I searched my batch/build files I can't find where that change occurs

Answer 1

Thats the down side of external links in an accepted answer. Codehaus shut down and thus the solution is gone. For reference here's the content behind the link - you basically only need to copy the <dependencies>...</dependencies> block to your antrun plugin...
The maven-antrun-plugin runs ant with JAVA_HOME set to the jre subdirectory of the JDK, even if the JAVA_HOME for the overall run is a JDK.
There is documentation elsewhere about how to create a dependency at the project level for the JDK's tools.jar, but this does not help out antrun, which is a plugin.
The following profile does the job. The '..' in the path hauls up past the 'jre' directory to the lib directory.
<profiles>
<profile>
<id>tools.jar</id>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-antrun-plugin</artifactId>
<dependencies>
<dependency>
<groupId>com.sun</groupId>
<artifactId>tools</artifactId>
<version>1.5.0</version>
<scope>system</scope>
<systemPath>${java.home}/../lib/tools.jar</systemPath>
</dependency>
</dependencies>
</plugin>
</plugins>
</build>
</profile>

Answer 2

I was able to fix this by putting the following property definition in my ant build.xml file:
<property name="build.compiler" value="extJavac"/>