java/shellscript code to find out if a jar file is already running on current machine

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-上瘾入骨i
-上瘾入骨i 2021-01-03 02:44

How do I find out if a specific JAR file is running on my machine or not? I just want to ensure that a specific JAR is only executed once at any time-- so if another request

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  • 2021-01-03 03:09

    jps is a simple command-line tool that prints out the currently running JVMs and what they're running. You can invoke this from a shell script.

    jps -l will dump out the JVM process id and the main class that it's executing. I suspect that's the most appropriate for your requirement.

    Noting your comment re. jps being not supported, if it's a valid worry that you can't easily mitigate via testing when you upgrade a JDK/JRE, then perhaps use something like:

    pgrep -lf java
    
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  • 2021-01-03 03:17

    Try to create a new jar,

    create a class inside with like this (not yet functional code, just a scribble):

    static ServerSocket unicorn;
    public void load(){
        unicorn=new ServerSocket(39483); // whatever-port
    
        URLClassLoader myloader = new URLClassLoader(new URL[]{this.getClass().getResource("/META-INF/specific.jar")});
        ... // do all your unique stuff
        Runtime.addShutdownHook(new Runnable(){unicorn.close();})
    }
    

    Place your specific.jar inside the new.jar. If ever another instance of this jar try to be load, a exception will be thrown: Socket already in use.

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