Reading content of a JAR file (at runtime)? [duplicate]

Answer 1

Here is how I read it as a ZIP file,

   try {
        ZipInputStream is = new ZipInputStream(new FileInputStream("file.jar"));
        ZipEntry ze;

        byte[] buf = new byte[4096];
        int len;

        while ((ze = is.getNextEntry()) != null) {

            System.out.println("----------- " + ze);
            len = ze.getSize();

            // Dump len bytes to the file
            ...
        }
        is.close();
    } catch (Exception e) {
        e.printStackTrace();
    }

This is more efficient than JarFile approach if you want decompress the whole file.

Answer 2

Here is the complete code which reads all the file contents inside the jar file.

public class ListJar {
    private static void process(InputStream input) throws IOException {
        InputStreamReader isr = new InputStreamReader(input);
        BufferedReader reader = new BufferedReader(isr);
        String line;

        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
        reader.close();
    }

    public static void main(String arg[]) throws IOException {
        JarFile jarFile = new JarFile("/home/bathakarai/gold/click-0.15.jar");

        final Enumeration<JarEntry> entries = jarFile.entries();
        while (entries.hasMoreElements()) {
            final JarEntry entry = entries.nextElement();
            if (entry.getName().contains(".")) {
                System.out.println("File : " + entry.getName());
                JarEntry fileEntry = jarFile.getJarEntry(entry.getName());
                InputStream input = jarFile.getInputStream(fileEntry);
                process(input);
            }
        }
    }
}

Answer 3

You use JarFile to open a Jar file. With it you can get ZipEntry or JarEntry (they can be seen as the same thing) by using 'getEntry(String name)' or 'entires'. Once you get an Entry, you can use it to get InputStream by calling 'JarFile.getInputStream(ZipEntry ze)'. Well you can read data from the stream.

See a tutorial here.