Monday Mar 03, 2008

Listing Java Process from Java

Month Ago, one of my colleagues was making an application, actually the UI flavor of JStack. Since JStack asks you the process ID for attaching the particular Java Application with JStack. In a UI based tool, telling user to do Alt-Ctrl-Del and see the process ID,not sounds good. So, my first impression was that you have to show the java process in the drop down and user will select in that. Some day back even, I want to find all process running on my machine from java code for some stupid purpose. I am trying to write some code for both of them. Java can't play with system process and hence invoking a runtime is only solution to get all process and here it is:


import java.io.\*;
class ListProcess {
public static void main(String[] args)throws IOException
{
          Runtime runtime = Runtime.getRuntime();
           String cmds[] = {"cmd", "/c", "tasklist"};
           Process proc = runtime.exec(cmds);
           InputStream inputstream = proc.getInputStream();
           InputStreamReader inputstreamreader = new InputStreamReader(inputstream);
           BufferedReader bufferedreader = new BufferedReader(inputstreamreader);
           String line;
           while ((line = bufferedreader.readLine()) != null) {
               System.out.println(line);
           }
}
}


Code is written exclusively for Windows Machine :). And one line change in this code will list you only java running process.

String cmds[] = {"cmd", "/c", "jps"}; this is nothing but running jps.exe file in bin (jdk6 onwards). Its not all done. Writting Runtime code is not the real solution as there is little of platform dependencies. So, I have decide to write the code for getting List of Java Process. Again, I have checked by OpenJDK code for jps(search on jps.java file :) ) and I got some hint how to do it and here it goes:

import java.util.\*;
import sun.jvmstat.monitor.\*;

public class ListJavaProcess {
   public static void main(String[] args) throws Exception {

    /\* Checking for local Host, one can do for remote machine as well \*/
          MonitoredHost local = MonitoredHost.getMonitoredHost("localhost");
    /\* Take all active VM's on Host, LocalHost here \*/
     Set vmlist = new HashSet(local.activeVms());
     for (Object id : vmlist) {
       /\* 1234 - Specifies the Java Virtual Machine identified by lvmid 1234 on an unnamed host.
       This string is transformed into the absolute form //1234, which must be resolved against
       a HostIdentifier. \*/
     MonitoredVm vm = local.getMonitoredVm(new VmIdentifier("//" + id));
       /\* take care of class file and jar file both \*/
    String processname = MonitoredVmUtil.mainClass(vm, true);
       System.out.println(id + " ------> " + processname);
     }
   }
}


I have written good amount of comment as it is all together a sun import rather than java or javax import. This import resides in tools.jar, so even running simple javac and java will not work. So, running the program will go here:


E:\\Program Files\\Java\\jdk1.6.0_10\\bin>javac -classpath "E:\\Program Files\\Java\\jd
k1.6.0_10\\lib\\tools.jar" ListJavaProcess.java


E:\\Program Files\\Java\\jdk1.6.0_10\\bin>java -classpath .;"E:\\Program Files\\Java\\j
dk1.6.0_10\\lib\\tools.jar" Vista

3700 ------> ListJavaProcess

Right now only one java process is running. Now in the second code, you can play with some of the java process, but with native process in the above code you can't do anything except watching it :)

No idea how to do this in JDK 1.5 or backwards.



About

Hi, I am Vaibhav Choudhary working in Sun. This blog is all about simple concept of Java and JavaFX.

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