How do you make a function that will create a .jar file in Java?

Question

I've made some code in Java that will change some files in another .jar file, and I know that the unpacking/changing works, but the repacking doesn't. It does succeed, but when I compare the new one and the original (I removed the code that changed the files), they differed. What's interesting is that when I extracted them both into different directories, and I runned diff -rqy on them both, it didn't show any difference.

Here is the current function:

public static void add(File source, JarOutputStream target, String removeme)
        throws IOException
{
    BufferedInputStream in = null;
    try
    {
        File source2 = new File(source.getPath().replaceAll("^" + removeme,
                ""));
        // File source2 = source;
        if (source.isDirectory())
        {
            String name = source2.getPath().replace("\\", "/");
            if (!name.isEmpty())
            {
                if (!name.endsWith("/"))
                    name += "/";
                JarEntry entry = new JarEntry(name);
                entry.setTime(source.lastModified());
                target.putNextEntry(entry);
                target.closeEntry();
            }
            for (File nestedFile : source.listFiles())
                add(nestedFile, target, removeme);
            return;
        }

        JarEntry entry = new JarEntry(source2.getPath().replace("\\", "/"));
        entry.setTime(source.lastModified());
        target.putNextEntry(entry);
        in = new BufferedInputStream(new FileInputStream(source));

        byte[] buffer = new byte[2048];
        while (true)
        {
            int count = in.read(buffer);
            if (count == -1)
                break;
            target.write(buffer, 0, count);
        }
        target.closeEntry();
    }
    finally
    {
        if (in != null)
            in.close();
    }
}

I call it like this:

JarOutputStream zip = new JarOutputStream(
                        new FileOutputStream(JARFILE));
                for (File nestedFile : new File(DIRECTORY).listFiles())
                {
                    Utils.add(nestedFile, zip,
                            new File(DIRECTORY).getAbsolutePath());
                }
                zip.close();

Can anyone direct me on what to change in the function, or what other function I should use? The directory has subdirectories, so I need a function that will scan them.

Thanks in advance!

Edit: I don't want something using the jar command, because I don't want the user to need to install the JDK. I want something using pure Java (libraries are OK, as long as I can include them in the program).

Edit 2: I'm making a Minecraft modder (like MCPatcher and ModLoader), but when I run java -jar minecraft.jar , it gives me this: Invalid or corrupt jarfile . The correct .jar doesn't give this (just a main class error, which is supposed to happen).

Answer 1

I think you maybe interested in java.util.jar. This link maybe useful for you..

http://www.theserverside.com/discussions/thread.tss?thread_id=32600