Ant build not working: unable to find a javac compiler

Question

I am trying to run some Java EE examples. Ant is suggesting: Perhaps JAVA_HOME does not point to the JDK. It is currently set to "C:\Program Files\Java\jre7

My JAVA_HOME variable is: C:\Program Files\Java\jdk1.7.0_03 when I look at my windows 7 variables

However, my path is (notice the jdk1.6.0_26):

%M2_HOME%\bin;%ANT_HOME%\bin;%JAVA_HOME%\bin;%SystemRoot%\system32;%SystemRoot%;
%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\;
C:\Program Files\Microsoft Application Virtualization Client;%M2%;
C:\Program Files\QuickTime\QTSystem\;C:\Program Files\TortoiseSVN\bin;
%GLASSFISH%;%GLASSFISH_PARENT%;

PATH=C:\Maven\apache-maven-2.2.1\bin;C:\Ant\apache-ant-1.8.2\bin;**C:\Program File
s\Java\jdk1.6.0_26\bin;**C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C
:\Windows\System32\WindowsPowerShell\v1.0\;C:\Program Files\Microsoft Applicatio
n Virtualization Client;C:\Maven\apache-maven-2.2.1\bin;C:\Program Files\QuickTi
me\QTSystem\;C:\Program Files\TortoiseSVN\bin;C:\glassfish3\glassfish\bin;C:\gla
ssfish3\bin;C:\Sun\jwsdp-2.0\jwsdp-shared\bin

Do I have to do anything special to get windows to save my path?

More Info:

C:\javaeetutorial5\examples\web\hello2>ant
Unable to locate tools.jar. Expected to find it in C:\Program Files\Java\jre7\li
b\tools.jar
Buildfile: C:\javaeetutorial5\examples\web\hello2\build.xml

-pre-init:

init:

default-ear:

-pre-compile:

bpp-actual-compilation:
     [echo] Compiling hello2
     [echo] javaee.classpath.prefix is: C:\glassfish3/lib
     [echo] is.glassfish.v3 is: ${is.glassfish.v3}
    [javac] C:\javaeetutorial5\examples\bp-project\command-line-ant-tasks.xml:93
: warning: 'includeantruntime' was not set, defaulting to build.sysclasspath=las
t; set to false for repeatable builds

BUILD FAILED
C:\javaeetutorial5\examples\bp-project\command-line-ant-tasks.xml:93: 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:\Program Files\Java\jre7"

Total time: 0 seconds

Solution 1

For eclipse

• Right Click build.xml ---> Build path ---> configure buildpath ---> select libraries tab
• click "Add library" ---> double click on [jre system library ] ---> environments ---> installed jres ---> Add ---> standard vm
• click on directory ---> Browse upto jdk [C:\Program Files\Java\jdk1.7.0_01]
• finish
• change the selection jre to jdk ---> click ok

Solution 2

Quick work around for the same is

Copy C:\Program Files\Java\jdk1.7.0_03\lib\tools.jar to C:\Program Files\Java\jre7\lib\

This exception is coming because JAVA_HOME is being set as C:\Program Files\Java\jre7 and Ant is not able to find tools.jar in it.

Solution 3

In windows, go to computer properties, advanced system settings, advanced, environment variables

Add a system variable called "JAVA_HOME" set its folder to your JDK location in my case "C:\Program Files\Java\jdk1.7.0_51"

Close command prompt, reopen it and it should work now.

Solution 4

When you have both JRE and JDK installed in your system, please make sure JDK comes first in your PATH variable.

I think system scans the PATH variable from left to right, whatever comes first is taken into consideration.

In my case (with LinuxMint ) I was getting the same error. When I added JDK in PATH variable before JRE , it solved my problem.

Solution 5

I was getting the same error in Mac OS X but all the answers I could find were for the Windows system and as the paths are a little different in both, those solutions weren't working for me. After spending hours on it, I was finally able to fix it in the following way:

Copy /Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home/lib/tools.jar to /Library/Java/JavaVirtualMachines/jdk1.8.0_91.jdk/Contents/Home/jre/lib/ext

It will work for Windows users too:

Copy C:\Program Files\Java\jdk1.8.0_91\lib\tools.jar to C:\Program Files\Java\jre8\lib\ext

P.S. Also take care that the versions for jdk and jre that you have selected in Eclipse are compatible.

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