How to set a long Java classpath in Windows?

Question

I\'m trying to run a particular JUnit test by hand on a Windows XP command line, which has an unusually high number of elements in the class path. I\'ve tried several varia

Answer 1

There was no solution to the issue other than somehow making the classpath shorter by moving the jar files into a folder like "C:\jars".

Answer 2

Since Java 6 you can use classpath wildcards.

Example: foo/*, refers to all .jar files in the directory foo

• this will not match class files (only jar files). To match both use: foo;foo/* or foo/*;foo. The order determines what is loaded first.
• The search is NOT recursive

Answer 3

Have you tried stacking them?

set CLASS_PATH = c:\path
set ALT_A = %CLASS_PATH%\a\b\c;
set ALT_B = %CLASS_PATH%\e\f\g;
...

set ALL_PATHS = %CLASS_PATH%;%ALT_A%;%ALT_B%

Answer 4

(I suppose you do not really mean DOS, but refer to cmd.exe.)

I think it is less a CLASSPATH limitation than an environment size/environment variable size limit. On XP, individual environment variables can be 8k in size, the entire environment is limited to 64k. I can't see you would hit that limit.

There is a limit on windows that restricts the length of a command line, on WindowsNT+ it is 8k for cmd.exe. A set command is subject to that restriction. Can it be you have more than 8k worth of directories in your set command? You may be out of luck, then - even if you split them up like Nick Berardi suggested.

Answer 5

If I were in your shoes, I would download the junction utility from MS : http://technet.microsoft.com/en-us/sysinternals/bb896768.aspx and then map your "C:\path" to say, "z:\" and "c:\path2" to say, "y:\". This way, you will be reducing 4 characters per item in your classpath.

set CLASS_PATH=C:\path\a\b\c;C:\path\e\f\g;
set CLASS_PATH=%CLASS_PATH%;C:\path2\a\b\c;C:\path2\e\f\g;

Now, your classpath will be :

set CLASS_PATH=z\a\b\c;z\e\f\g;
set CLASS_PATH=%CLASS_PATH%;y:\a\b\c;y:\e\f\g;

It might do more depending on your actual classpath.

Answer 6

The Windows command line is very limiting in this regard. A workaround is to create a "pathing jar". This is a jar containing only a Manifest.mf file, whose Class-Path specifies the disk paths of your long list of jars, etc. Now just add this pathing jar to your command line classpath. This is usually more convenient than packaging the actual resources together.

As I recall, the disk paths can be relative to the pathing jar itself. So the Manifest.mf might look something like this:

Class-Path: this.jar that.jar ../lib/other.jar

If your pathing jar contains mainly foundational resources, then it won't change too frequently, but you will probably still want to generate it somewhere in your build. For example:

<jar destfile="pathing.jar">
  <manifest>
    <attribute name="Class-Path" value="this.jar that.jar ../lib/other.jar"/>
  </manifest>
</jar>