How do I read the manifest file for a webapp running in apache tomcat?

Question

I have a webapp which contains a manifest file, in which I write the current version of my application during an ant build task. The manifest file is created correctly, but when I try to read it in during runtime, I get some strange side-effects. My code for reading in the manifest is something like this:

    InputStream manifestStream = Thread.currentThread()                                  .getContextClassLoader()                                  .getResourceAsStream("META-INFFFF/MANIFEST.MF");     try {         Manifest manifest = new Manifest(manifestStream);         Attributes attributes = manifest.getMainAttributes();         String impVersion = attributes.getValue("Implementation-Version");         mVersionString = impVersion;     }     catch(IOException ex) {         logger.warn("Error while reading version: " + ex.getMessage());     } 

When I attach eclipse to tomcat, I see that the above code works, but it seems to get a different manifest file than the one I expected, which I can tell because the ant version and build timestamp are both different. Then, I put "META-INFFFF" in there, and the above code still works! This means that I'm reading some other manifest, not mine. I also tried

this.getClass().getClassLoader().getResourceAsStream(...) 

But the result was the same. What's the proper way to read the manifest file from inside of a webapp running in tomcat?

Edit: Thanks for the suggestions so far. Also, I should note that I am running tomcat standalone; I launch it from the command line, and then attach to the running instance in Eclipse's debugger. That shouldn't make a difference, should it?

Answer 1

Maybe your side-effects come from the fact that almost all jars include a MANIFEST.MF and you're not getting the right one. To read the MANIFEST.MF from the webapp, I would say:

ServletContext application = getServletConfig().getServletContext(); InputStream inputStream = application.getResourceAsStream("/META-INF/MANIFEST.MF"); Manifest manifest = new Manifest(inputStream); 

Please note that running Tomcat from Eclipse is not the same as running Tomcat alone as Eclipse plays with the classloader.