in eclipse plug-in, programmatically save new .java files to an existing jar file in the workspace

Question

I'm writing a plug-in for Eclipse Standard/SDK Kepler to give diagnostic feedback to undergraduate student programmers as they work on their Java programming assignments. The student can run my plug-in as often as he wishes to see if his code triggers any messages about poor programming practices he might want to change.

Each time the student invokes the plug-in, I need to save a copy of all the .java files in the student's project as well as a text file containing the diagnostic feedback produced by the plug-in. I don't want to make the student use a file export wizard, so I figured out how to programmatically create a jar file using the JarPackageData and JarWriter3 classes from org.eclipse.jdt.ui.jarpackager . That works for the first time I save files, but I don't want to create a new jar each time the student runs the plug-in. When the student runs my plug-in for the second (third, fourth…) time I want to add more files to the jar I already made so that I end up with a single jar file that contains a complete record of the student's use of my plug-in.

JarWriter3 creates a new jar file but does not provide any methods to add to a jar that already exists. I have searched both the Eclipse documentation and the stackoverflow archive, so far without success. One answer to a previous question explained how to write a jar file using the java.util.jar.JarEntry and JarOutputStream classes, but I thought I should stick with functionality provided by Eclipse classes if indeed there are any that will solve my problem.

Answer 1

JarWriter3 is essentially just a fairly thin wrapper around JarOutputStream , for example the constructor opens the jar output stream with:

if (fJarPackage.usesManifest() && fJarPackage.areGeneratedFilesExported()) {
  Manifest manifest = fJarPackage.getManifestProvider().create(fJarPackage);
  fJarOutputStream = new JarOutputStream(new BufferedOutputStream(new FileOutputStream(fJarPackage.getAbsoluteJarLocation().toFile())), manifest);
} else
  fJarOutputStream = new JarOutputStream(new BufferedOutputStream(new FileOutputStream(fJarPackage.getAbsoluteJarLocation().toFile())));

so I would be inclined to just use the standard Java JarOutputStream and JarEntry .

If you are saving the jar in the workspace you will need to call IFile.refreshLocal once the jar is written to get it recognised by Eclipse.