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 to execute the same jar comes in then I should not again invoke that jar.
I can use code for the above either as java code (which I will add to that JAR itself) or as shellscript (which I will use to invoke the jar file).
The machine will be a Linux machine-- either CentOS, or Debian or Ubuntu or Amazon Linux.
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
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.
