How to use JarOutputStream to create a JAR file?

Gili_14731 0
Viewed 46256

How does one create a JAR file programmatically using java.util.jar.JarOutputStream? The JAR file produced by my program looks correct (it extracts fine) but when I try loading a library from it Java complains that it cannot find files which are clearly stored inside it. If I extract the JAR file and use Sun's jar command-line tool to re-compress it the resulting library works fine. In short, something is wrong with my JAR file.

Please explain how to create a JAR file programmatically, complete with a manifest file.

jar java
6 Answers

You can do it with this code:

public void write(File[] files, String comment) throws IOException {
    FileOutputStream fos = new FileOutputStream(PATH + FILE);
    JarOutputStream jos = new JarOutputStream(fos, manifest);
    BufferedOutputStream bos = new BufferedOutputStream(jos);
    jos.setComment(comment);
    for (File f : files) {
        print("Writing file: " + f.toString());
        BufferedReader br = new BufferedReader(new FileReader(f));
        jos.putNextEntry(new JarEntry(f.getName()));
        int c;
        while ((c = br.read()) != -1) {
            bos.write(c);
        }
        br.close();
        bos.flush();
    }
    bos.close();
//  JarOutputStream jor = new JarOutputStream(new FileOutputStream(PATH + FILE), manifest);

}

PATH variable: path to JAR file

FILE variable: name and format

user_70134600

Ok, so by request, here's Gili's code, modified to use relative paths rather than absolute ones. (Replace "inputDirectory" with the directory of your choice.) I just tested it, but if it doesn't work, lemme know.

   public void run() throws IOException
   {
      Manifest manifest = new Manifest();
      manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
      JarOutputStream target = new JarOutputStream(new FileOutputStream("output.jar"), manifest);
      File inputDirectory = new File("inputDirectory");
      for (File nestedFile : inputDirectory.listFiles())
         add("", nestedFile, target);
      target.close();
   }

   private void add(String parents, File source, JarOutputStream target) throws IOException
   {
      BufferedInputStream in = null;
      try
      {
         String name = (parents + source.getName()).replace("\\", "/");

         if (source.isDirectory())
         {
            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(name, nestedFile, target);
            return;
         }

         JarEntry entry = new JarEntry(name);
         entry.setTime(source.lastModified());
         target.putNextEntry(entry);
         in = new BufferedInputStream(new FileInputStream(source));

         byte[] buffer = new byte[1024];
         while (true)
         {
            int count = in.read(buffer);
            if (count == -1)
               break;
            target.write(buffer, 0, count);
         }
         target.closeEntry();
      }
      finally
      {
         if (in != null)
            in.close();
      }
   }
user_5130380

This answer would solve the relative path problem.

private static void createJar(File source, JarOutputStream target) {
        createJar(source, source, target);
    }

    private static void createJar(File source, File baseDir, JarOutputStream target) {
        BufferedInputStream in = null;

        try {
            if (!source.exists()){
                throw new IOException("Source directory is empty");
            }
            if (source.isDirectory()) {
                // For Jar entries, all path separates should be '/'(OS independent)
                String name = source.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()) {
                    createJar(nestedFile, baseDir, target);
                }
                return;
            }

            String entryName = baseDir.toPath().relativize(source.toPath()).toFile().getPath().replace("\\", "/");
            JarEntry entry = new JarEntry(entryName);
            entry.setTime(source.lastModified());
            target.putNextEntry(entry);
            in = new BufferedInputStream(new FileInputStream(source));

            byte[] buffer = new byte[1024];
            while (true) {
                int count = in.read(buffer);
                if (count == -1)
                    break;
                target.write(buffer, 0, count);
            }
            target.closeEntry();
        } catch (Exception ignored) {

        } finally {
            if (in != null) {
                try {
                    in.close();
                } catch (Exception ignored) {
                    throw new RuntimeException(ignored);
                }
            }
        }
    }
user_78718520
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