Java Find the absolute path of dependent jar

I have Jar file which dependency on another project jar. Both are thin jars and are at same location. 1st jar has manifest file which list second jar in its class-path property.

In 1st jar I am launching second jar as a process using ProcesBuilder class in java. To do so I need absolute path of second jar. In 1st jar i have class XClient
If I do XClient.class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath();
i am getting absolute path of 1st jar. Then I can split and add the name of second jar(hard-coded) to build the absolute path

In second jar I have class XServer
If I do

 XServer .class.getProtectionDomain().getCodeSource().getLocation().toURI().getPath();

Its throws exception

I am not sure if I am doing the right approach but my goal is very clear I wanted to get the absolute path to the dependent jar.

Please help

I tried to use the same approach (but used File file=new File(this.getClass().getProtectionDomain().getCodeSource().toUri()) instead of getPath()) but this can fail in different ways:

1. when the class is inside a jar the File object points to the jar instead the folder the jar is in - so an if(file.isFile()) file=file.getParentFile(); is needed to get the directory instead of the jar file
2. when the jar file is loaded by something other than the usual URLClassLoader (last time I tried was back in 1.8 - and I only know that since Jigsaw the main classloader can't be cast to an URLClassLoader anymore) this may will return some unspecified result, if at all, so actual behaviour depends on the very system setup - wich can make it difficult to debug when used on a remote system not under your control
3. UNC paths (Windows shares) are error prone by themselfs - adding another layer on top of it (java) just add a lot of potential other pitfalls you all have to test and debug - wich often ends up you tell the client what to use and how to setup instead of design your code to follow the java principle: "write once, compile once, run everywhere" (btw: this also applies even if you "mount" a network share so you can address it by a local drive letter instead of a remote network path - but this even causes problems when you try to link two machines where one is a clone of the other)
4. as already mentioned as comment: "it doesn'T work" is not a usefull or meaningfull description - if you get an error message (in this case as you mentioned an exception stacktrace) post it along with the code wich produced it (if accessible)

How I solved my problem? I just ask the user for the directory / file by a swing JFileChooser. Yes, this isn't fool proof and maybe not the best way - but it works as swing still ships with SE JVM (instead of FX).
If you want to find a path use Class.getResource() and let java do the work, pretty much like crypto: don'T do your own.

Aside from all that: Your mentioned "usecase" doesn'T require what you try to do. You said that the server is already in the classpath - so it gets loaded on startup and you can access the XServer class. The easiest way instead of forking another process is to just run it in another thread. If you know wich class has the main (the manifest of the server.jar will tell you) and you can access it in classpath just do something like this:

Thread serverThread=new Thread(new Runnable()
{
	public void run()
	{
		String[] args=Arrays.asList("required", "parameters");
		XServer.main(args);
	}
});
serverThread.start();

If no paramters required you can just pass an empty String array. As main() should not throw Exceptions (at least no checked ones) no exception should be needed.

Before all those comments are thrown at me: Yes, I am very well aware of possible issues with such approach like classpath issues (same classname in same packagename but different versions) and such it may be more feasible than try to figure out the absolute path and launch a fork / sub process.
Also: Starting another process may require to interact with its streams (provide required input into child process inputstream and read the child process outputstream and errorstream - otherwise the forked process may can "hang" as it waits for the pipelines to get cleared. It's a pain in the but to debug that kind of issue if it's not your own code and you can have a profiler and debugger attached to it to figure out why all just suddenly stopped to work.

If you really want to (I don't think there's any requirement forcing a "you need to") launch your server along with the client do it with a launch script outside of java but with os level stuff.