Why does ANT tell me that JAVA_HOME is wrong when it is not?

Solution 1:

1. In Eclipse click Run → External Tools → External Tools Configurations.
2. Click the JRE tab.
3. Click the Installed JREs... button.
4. Click the Add button.
   (Select Standard VM, where applicable.)
5. Click the Directory button.
6. Browse to your JDK version (not JRE) of your installed Java
   (e.g. C:\Program Files\Java\jdk1.7.0_04).
7. Click Finish and OK.
8. Select the JDK at Separate JRE and click Close.
9. Re-run your Ant script — have fun!

This worked in a particular scenario I encountered.

Solution 2:

When you say you have "clearly set" JAVA_HOME to "C:\Program Files\Java\jdk1.6.0_14" - is that what you see when you run "set" from the command line? I believe Ant will guess at a value for JAVA_HOME if one isn't set at all... is it possible that you've set JAVAHOME instead of JAVA_HOME?

If it's nothing like that, I suggest you edit the ant.bat batch file (and whatever it calls - I can't remember whether it's convoluted or not offhand) to print out JAVA_HOME at the start and at various other interesting places.

Solution 3:

I encountered the same problem when I try to run Ant build using the following command:

java -cp ant.jar:ant-launcher.jar org.apache.tools.ant.Main

The output of the command is:

BUILD FAILED
XXX/build.xml:8: 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 "/usr/lib/jvm/java-6-openjdk/jre"

It seems the java executable is picking "/usr/lib/jvm/java-6-openjdk/jre" as JAVA_HOME, as opposed to "/usr/lib/jvm/java-6-openjdk" where JDK is installed.

I resolved this issue by setting fork="yes" in my <javac> task.

Take a look at: http://ant.apache.org/manual/Tasks/javac.html