ant error: unable to find a javac compiler

I was using ant 1.5 with no problems until recently...then upgraded to 1.6 and had all sorts of problems so have gone back to 1.5. Now I get the error:

(JAVA_HOME is correct) when trying to compile anything. I've read a ton of posts about this, all of which say to copy tools.jar into $ANT_HOME/lib - I've done that and still got the problem. Any ideas?

TIA

unable to find a javac compiler

I have a similar problem using Ant 1.6 on Windows.

This is unfortunately not a solution to your question.

I have a similar problem to yours so when you find out the answer I'd like to know what it is!

(I also tried the kludgey fix of copying tools.jar to %ANT_HOME%\lib but that didn't work.)

John (September 26th 2004)
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The command I was using was 'ant doc', within a directory containing a build.xml file.

In the original ant.bat, the following statement was being used:

"%_JAVACMD%" %ANT_OPTS% -classpath "%ANT_HOME%\lib\ant-launcher.jar" "-Dant.home=%ANT_HOME%" org.apache.tools.ant.launch.Launcher %ANT_ARGS% -lib "%CLASSPATH%" %ANT_CMD_LINE_ARGS%

Maybe the setting of classpath by -classpath "%ANT_HOME%\lib\ant-launcher.jar"
was the problem.

I modified ant.bat to be as simple as possible. This resulted in a statement close to the manual-recommended minimal statement:-

java -Dant.home=c:\ant org.apache.tools.ant.launch.Launcher

When I ran this, at least I didn't get a NullPointerException error as the Launcher and Main were found and ran OK.

My environment variables are
%ANT_HOME%\lib\ant.jar;%ANT_HOME%\lib\ant-launcher.jar included in CLASSPATH
%ANT_HOME%\bin included in PATH]

----

However, now when build.xml gets to the property
<javac srcdir="${src}"
destdir="${build}"
excludes="**/*.java.*"
/>

Then this error is shown:-

init:

prepare:

compile:
[javac] Compiling 3 source files to C:\JimDemo\Pets02\build
BUILD FAILED
c:\JimDemo\pets02\build.xml:30: 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

----

The main statement in the ant.bat file is :-
"%_JAVACMD%" "-Dant.home=%ANT_HOME%" org.apache.tools.ant.launch.Launcher %ANT_ARGS% %ANT_CMD_LINE_ARGS%

If I specify classpath after Launcher in the above statement,

"%_JAVACMD%" %ANT_OPTS% -classpath "%ANT_HOME%\lib\ant-launcher.jar" "-Dant.home=%ANT_HOME%" org.apache.tools.ant.launch.Launcher %ANT_ARGS% -lib "%CLASSPATH%" %ANT_CMD_LINE_ARGS%

in order to get %JAVA_HOME%\bin on the classpath, then I get a NullPointerException error due to not being able to find Launcher.

I get the same error (NullPointerException) if -lib %JAVA_HOME%\bin is placed after Launcher in the above statement instead of -lib "%CLASSPATH%.
----

Are you using ANT in eclipse by chance? If so, Ant fails this way because by default Eclipse uses the first Java.exe it finds to start with, and for some reason Eclipse/ANT look for javac.exe in this same location. If you look, there is a java.exe in the windows.system32 folder. To fix it I had to make the sdk path (c:\j2sdk1.4.2_04\bin;) the first thing in my PATH statement, before the window/system32 entry.

I am using Eclipse 2.1, so this may not be your issue.

EDIT: here are some other possible solutions
http://www.mjwall.com/node/view/134

nope, I'm trying to use ant on the command line - in fact, I can use it OK from within netbeans, which I think has it's own version of ant bundled within it...

This happened to me too when Jetty was trying to compile JSP files within a web application.
I was running jetty through the command line and you'll found out that this will solve your problem:

[Window]
set PATH=%ANT_HOME%\bin;%JAVA_HOME%\bin;%PATH%

[UNIX]

PATH=$ANT_HOME/bin:$JAVA_HOME/bin:$PATH

Good Luck