How to execute a class in a subdirectory in .jar file

[zeyarag]

Dear All,

I have a jar file "My.jar".
In this "My.jar" file, I have a directory "build\classes".
In this "build\classes" directory, I have a package "package1.sub1".
In this "package1.sub1", I have class files "MyClassA.class", "MyClassB.class", etc. (package package1.sub1 is declared in all of these classes.)

Now, I want to execute "package1.sub1.MyClassA.class" in "build\classes" directory of "My.jar" from the command line. How can I do that?

I tried "java -cp My.jar build\classes\package1.sub1.MyClassA.class", but it was not successful. Please help me.

Thank you very much.

Best regards,
Zeyar

[travishein]

I'm not sure why you would package the build/classes folder into the jar file.?
Usually you would create the jar file with the build/classes as the base directory, so that the first folder inside the jar file would be package1/ and then the command line "java -cp My.jar package1.sub1.MyClassA" (also without the .class extension) would just work.

In theory it is technically possible to get the files inside build/classes inside the jar file to work, this can be done by creating a bootstrap piece of Java code that lives in the top level of the jar file that unpacks the jar file to a temporary location and then installs a URL class loader kind of class loader to refer to the build/classes/ where it now exists in this temporary folder to have it added onto the classpath. But unless there was a very compelling reason to do this, I would say just change how you build your jar file to have the build/classes be the jar root.

For example, in Ant,

  <target name="make-jar">
    <jar jarfile="My.jar"  basedir="build/classes" />
  </target>

[zeyarag]

Dear Travishein,

Thank you very much for your kind help.

Best regards,
Zeyar