Setting JAVA_HOME when running Ant from Java

StackOverflow https://stackoverflow.com/questions/652053

  •  19-08-2019
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Question

The reason is long and boring, but I need to run an Ant script to compile Java 1.5 code from a Java 1.4 app. I keep getting this error, though:

BUILD FAILED

build.xml:16: 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:\j2sdk1.4.2_16\jre"

In my code, I have:

Project p = new Project();
p.setUserProperty("ant.file", buildFile.getAbsolutePath());
p.setProperty("java.home", "C:\Program Files\Java\jdk1.6.0_04");
p.fireBuildStarted();
p.init();
// so on and so forth

but it ignores it. I've also tried p.setUserProperty(String, String), but that doesn't do the trick, either. Is there a way to do it without launching a separate process?

Was it helpful?

Solution

Does the javac task in your buildfile have fork="yes"? If not, then it doesn't matter what the java.home property is set to; ant will attempt to call the javac Main method in the same java process, which from your error is a JRE, not a JDK.

EDIT Try setting the executable property of your javac task to the full path to the javac binary and add compiler="extJavac" to the task.

OTHER TIPS

Shouldn't the backslashes be doubled?

p.setProperty("java.home", "C:\\Program Files\\Java\\jdk1.6.0_04");

Have you set environment variables JAVA_HOME and ANT_HOME properly? If you are setting via code it should work though.

Also check if your %JAVA_HOME%\bin directory %ANT_HOME%\bin should be in the environment variable 'path'.

Your problem seems to be with the %JAVA_HOME%\bin not being present in the envt. variable path though.

Another way to make this work is to add 'tools.jar' to your classpath. The javac compiler is contained within this jar.

java -cp $JAVA_HOME/lib/tools.jar ...

javac option is available in tools.jar. In eclipse, even if your JRE HOME points to a jdk, all the system libraries point to JDK_HOME\jre\lib. There is no tools.jar. You can add tools.jar as an external Jar file. This should solve your issue

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