Ant “JAVA_HOME does not point to the JDK” - but it

问题:

I cannot run my Ant build.xml since I updated to java 1.7.0_52 (or there about). I have been running it for years through Eclipse locally on my Windows 7 laptop - but with this latest jave jdk update somethings different (?).

BUILD FAILED
C:\workspace\WaterAspectsModel3\build.xml:329: 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 "D:\Morten\Java\jdk1.7.0_52"

This is my jdk! So JAVA_HOME is pointing to a jdk (as is also clear from the error message). I have my JAVA_HOME with bin folder in my path as always. I've configured Eclipse - external tools configuration - with a JRE pointing to the same D:\Morten\Java\jdk1.7.0_52 (through "Separate JRE" setting). And I've tried a number of other configurations - all without luck.

I've been reading the tonnes of answers on lists here and other places and think I've tried all suggestions. Most seem to be cases where JAVA_HOME actually points to a jre and just needs to be corrected to jdk or there's a ";" in the path or something like that. None of these seem to apply in my case.

Any suggestions?

回答1:

The real message is that Ant can't find com.sun.tools.javac.Main.

Which, together with the fact that the latest "Sun" (Oracle) JDK is 1.7.0_13 (or maybe _14, but definitely not the "_52" that your install dir indicates), makes me think that you're not using a distribution that Ant recognizes. You can verify this by running jar tvf $JAVA_HOME/lib/tools.jar, and looking for that class.

The Ant Manual talks about ways to work with different compilers. Since I've only used "Sun" compilers, I'm afraid that I can't give you any pointers.

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Edit: you could also try setting fork="yes" in your build file. This should run the compiler executable rather than trying to invoke the compiler class.

回答2:

I was having the same message when running ANT through Eclipse.

What worked for me:

1. In Eclipse, access the menu: "Window -> Preferences";
2. Access "Ant -> Runtime", at the tree;
3. Access the Classpath tab;
4. Expand the "Global Entries" item;
5. Inside Global Entries, the path to tools.jar was wrong. It was pointing to an older version of Java;
6. I removed the wrong entry and added the correct one with "Add External Jars" button. It worked.

回答3:

The solution "Had to copy C:\Program Files\Java\jdk1.6.0_10\lib\tools.jar to C:\Program Files\Java\jre6\lib\ext" from here was great helpful and worked for me.

回答4:

Try adding JAVA_HOME\bin to your env PATH .

回答5:

Add JAVA_HOME to Eclipse-Preferences-Java-Build Path-Classpath Variables.