Reading My Own Jar's Manifest

Reading my own Jar's Manifest

You can do one of two things:

1. Call getResources() and iterate through the returned collection of URLs, reading them as manifests until you find yours:

   Enumeration<URL> resources = getClass().getClassLoader()
     .getResources("META-INF/MANIFEST.MF");
   while (resources.hasMoreElements()) {
       try {
         Manifest manifest = new Manifest(resources.nextElement().openStream());
         // check that this is your manifest and do what you need or get the next one
         ...
       } catch (IOException E) {
         // handle
       }
   }
   

2. You can try checking whether getClass().getClassLoader() is an instance of java.net.URLClassLoader. Majority of Sun classloaders are, including AppletClassLoader.
   You can then cast it and call findResource() which has been known - for applets, at least - to return the needed manifest directly:

   URLClassLoader cl = (URLClassLoader) getClass().getClassLoader();
   try {
     URL url = cl.findResource("META-INF/MANIFEST.MF");
     Manifest manifest = new Manifest(url.openStream());
     // do stuff with it
     ...
   } catch (IOException E) {
     // handle
   }
   

reading MANIFEST.MF file from jar file using JAVA

Next code should help:

JarInputStream jarStream = new JarInputStream(stream);
Manifest mf = jarStream.getManifest();

Exception handling is left for you :)

Using Java to read a .jar manifest file

The problem with using the jar tool is that it requires the full JDK to be installed. Many users of Java will only have the JRE installed, which does not include jar.

Also, jar would have to be on the user's PATH.

So instead I would recommend using the proper API, like this:

Manifest m = new JarFile("anyjar.jar").getManifest();

That should actually be easier!

Read META-INF/MANIFEST.MF from JAR

Depending on the class loader and the order of the JARs on the class path, this is just normal behavior. As there are multiple instances of /META-INF/MANIFEST.MF, which one you actually get is dependent on the class loader (that loaded the current class, as returned by getClass() in your code).

Instead, you can use ClassLoader.getResouces(String), which will give you an enumeration of all the manifests:

Enumeration<URL> manifests = getClass().getClassLoader().getResources("META-INF/MANIFEST.MF");

From that enumeration, you can look for the right one.

Another option, is using the Package class, which will give you easy access to the information from the manifest for your class/package:

Package myPackage = getClass().getPackage();
myPackage.getImplementationTitle();
myPackage.getImplementationVersion();
myPackage.getImplementationVendor();

Programmatically read Manifest.MF from JAR in an EAR

I manage to solve my problem by using this code:

JarFile myEAR = new JarFile(urlOfMyEAR);

File f = File.createTempFile("jar", null);
FileOutputStream resourceOS = new FileOutputStream(f);
byte[] byteArray = new byte[1024];
int i;

InputStream jarIS = myEAR.getInputStream(myEAR.getEntry(libname));
while ((i = jarIS.read(byteArray)) > 0) {
    //Write the bytes to the output stream
    resourceOS.write(byteArray, 0, i);
}
//Close streams to prevent errors
jarIS.close();
resourceOS.close();

JarFile myJAR = new JarFile(f);

Attributes m = myJAR.getManifest().getMainAttributes();

System.out.println(m.getValue("Implementation-Version"));

(thanks to this post https://stackoverflow.com/a/17902842/2454970)

the whole uncompressing takes only 7 seconds for a 7MB jar in a nearly 200MB ear...

thanks for your thoughts, guys.

Reading Manifest File Inside of Jar with Servlet

The Servlet context is /BotServlet/ not into the /BotServlet/WEB-INF/lib/Server_BotServlet.jar file. You could put a file you want to read in /WEB-INF/lib/myfile.txt and access that - or you could open the jar (/BotServlet/WEB-INF/lib/Server_BotServlet.jar) and read your MANIFEST. Really it depends on what your ultimate objectives are.

Read the jar version for a class

It seems I found some suitable solution here:
https://stackoverflow.com/a/37325538/4222206

So in the end this code can display the correct version of the jar (at least) in JBoss:

this.getClass().getPackage().getImplementationTitle();
this.getClass().getPackage().getImplementationVersion();

Hopefully I will find this answer when I search next time...

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