JarFile#entries do not show "META-INF" as a JarEntry when creating jar with JarOutputStream

Question

As per the link : /sf/answers/89690681/

I followed the instructions and created a jar file, the input directory where the source files for creating the jar is as follows,

• so (directory)
• so/some.txt (file)

when i am traversing through JarFile#entries method it is printing the following,

JarFile#entries output when jar created via JarOutputStream

META-INF/MANIFEST.MF
D:/so/
D:/so/some.txt

but i created the jar file using jar tool

Created jar using simple jar tool

jar -cvf so_commond.jar so so/some.txt
added manifest
adding: so/(in = 0) (out= 0)(stored 0%)
adding: so/some.txt(in = 7) (out= 9)(deflated -28%)

Now i use JarFile#entries to iterate the entries, the following is the output

JarFile#entries output when jar is created by jar tool

META-INF/ (this is not there when jar created by JarOutputStream)
META-INF/MANIFEST.MF
so/
so/some.txt

Could you please explain why the jar entry META-INF is shown only when jar is created by jar tool and does not shown when jar is created by JarOutputStream?

Code:

public static void main(String[] args){
  run();
    for(Enumeration<JarEntry> e = jf.entries(); e.hasMoreElements();){
                       System.out.println(e.nextElement().getName());
        }
 }

 public static void run() throws IOException
    {
        Manifest manifest = new Manifest();
        manifest.getMainAttributes().put(Attributes.Name.MANIFEST_VERSION, "1.0");
        JarOutputStream target = new JarOutputStream(new FileOutputStream("D:\\so.jar"),
                  manifest);
        add(new File("D:\\so"), target);
        target.close();
    }

    private static void add(File source, JarOutputStream target) throws IOException
    {
        BufferedInputStream in = null;
        try
        {
            if (source.isDirectory())
            {
                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())
                    add(nestedFile, target);
                return;
            }

            JarEntry entry = new JarEntry(source.getPath().replace("\\", "/"));
            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();
        }
    }

Answer 1

zip 文件格式中的目录是可选的。使用zip命令行工具时，可以使用 进行配置--no-dir-entries。