Using Java to read a .jar manifest file

Question

so I am trying to see if a .jar is valid or not, by checking some values in the mainfest file. What is the best way to read and parse the file using java? I thought of using thi

Answer 1

The easiest way is to use JarURLConnection class :

String className = getClass().getSimpleName() + ".class";
String classPath = getClass().getResource(className).toString();
if (!classPath.startsWith("jar")) {
    return DEFAULT_PROPERTY_VALUE;
}

URL url = new URL(classPath);
JarURLConnection jarConnection = (JarURLConnection) url.openConnection();
Manifest manifest = jarConnection.getManifest();
Attributes attributes = manifest.getMainAttributes();
return attributes.getValue(PROPERTY_NAME);

Because in some cases ...class.getProtectionDomain().getCodeSource().getLocation(); gives path with vfs:/, so this should be handled additionally.

Or, with ProtectionDomain:

File file = new File(getClass().getProtectionDomain().getCodeSource().getLocation().toURI());
if (file.isFile()) {
    JarFile jarFile = new JarFile(file);
    Manifest manifest = jarFile.getManifest();
    Attributes attributes = manifest.getMainAttributes();
    return attributes.getValue(PROPERTY_NAME);
}