Create JAR of the program itself

Question

I have a program that needs to be able to create an executable JAR-file of itself, but I'm unfortunately having some trouble making it work. This is the method I'm currently using to create the JAR:

public static void createJar() throws IOException {
    Manifest manifest = new Manifest();
    manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
    manifest.getMainAttributes().put(Attributes.Name.MAIN_CLASS, "JarTest");

    JarOutputStream jos = null;
    try {
       String jarPath = System.getProperty("user.dir") + "/Test.jar";
       jos = new JarOutputStream(new FileOutputStream(jarPath), manifest);
    }
    catch (IOException e) {e.printStackTrace();}

    ArrayList<String> fileList = new ArrayList<String>();
    String codeDir = System.getProperty("user.dir") + "/bin/jartest/";
    Files.list(Paths.get(codeDir)).forEach(entry -> {
        fileList.add(((Path)entry).toString());
    });

    int len = 0;
    byte[] buffer = new byte[1024];
    for(String file : fileList ) {
        //create JarEntry
        JarEntry je = new JarEntry(file);
        je.setComment("Creating Jar");
        je.setTime(Calendar.getInstance().getTimeInMillis());
        System.out.println(je);
        jos.putNextEntry(je);

        //write the bytes of file into jar
        InputStream is = new BufferedInputStream(new FileInputStream(file));
        while((len = is.read(buffer, 0, buffer.length)) != -1)
            jos.write(buffer, 0, len);
        is.close();
        jos.closeEntry();
        System.out.println("Done");
    }
    jos.close();
}

When I execute this no errors happen and I do get a JAR file called "Test.jar" generated in my Eclipse project folder. But when I open the JAR the .class files are not there, instead I see this:

I know that it's finding the .class files since the line System.out.println(je); successfully prints out the absolute path of each of them, so why aren't they getting put into the JAR?

It that some kind of exercise? Otherwise why not use the jar tool? — Henry, Apr 09 '16 at 12:44
It's an exercise to create a self-replicating program, like a computer worm. — Just some guy, Apr 09 '16 at 12:48
If you do `jar tvf Test.jar`, does it show expected entries and sizes? — Kedar Mhaswade, Apr 09 '16 at 13:04
@KedarMhaswade Yes, it does list the .class files with the correct sizes. So they are inside the JAR after all? But I cannot run it with 'java -jar Test.jar' (main class not found), and I cannot see any .class files when I open it with WinRAR. — Just some guy, Apr 09 '16 at 13:13
Duplicate? http://stackoverflow.com/questions/1281229/how-to-use-jaroutputstream-to-create-a-jar-file — Mike, Apr 09 '16 at 13:14

Just some guy · Accepted Answer · 2016-04-09T13:27:53.057

0

It solved itself when I changed these two lines:

String jarPath = System.getProperty("user.dir") + "/Test.jar";
String codeDir = System.getProperty("user.dir") + "/bin/jartest/";

To these:

String jarPath = "Test.jar";
String codeDir = "bin/jartest/";

I can now see the .class files inside the JAR.

edited Apr 09 '16 at 13:27

answered Apr 09 '16 at 13:20

Just some guy

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Create JAR of the program itself

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