How to get a list of current open windows/process

Question

Does any one know how do I get the current open windows or process of a local machine using Java?

What I'm trying to do is: list the current open task, windows or process open, like in Windows Taskmanager, but using a multi-platform approach - using only Java if it's possible.

Answer 1

Finally, with Java 9+ it is possible with ProcessHandle:

public static void main(String[] args) {
    ProcessHandle.allProcesses()
            .forEach(process -> System.out.println(processDetails(process)));
}

private static String processDetails(ProcessHandle process) {
    return String.format("%8d %8s %10s %26s %-40s",
            process.pid(),
            text(process.parent().map(ProcessHandle::pid)),
            text(process.info().user()),
            text(process.info().startInstant()),
            text(process.info().commandLine()));
}

private static String text(Optional<?> optional) {
    return optional.map(Object::toString).orElse("-");
}

Output:

    1        -       root   2017-11-19T18:01:13.100Z /sbin/init
  ...
  639     1325   www-data   2018-12-04T06:35:58.680Z /usr/sbin/apache2 -k start
  ...
23082    11054    huguesm   2018-12-04T10:24:22.100Z /.../java ProcessListDemo

Answer 2

Using code to parse ps aux for linux and tasklist for windows are your best options, until something more general comes along.

For windows, you can reference: http://www.rgagnon.com/javadetails/java-0593.html

Linux can pipe the results of ps aux through grep too, which would make processing/searching quick and easy. I'm sure you can find something similar for windows too.

Answer 3

This might be useful for apps with a bundled JRE: I scan for the folder name that i'm running the application from: so if you're application is executing from:

 C:\Dev\build\SomeJavaApp\jre-9.0.1\bin\javaw.exe

then you can find if it's already running in J9, by:

   public static void main(String[] args)
   {
    AtomicBoolean isRunning = new AtomicBoolean(false);
    ProcessHandle.allProcesses()
            .filter(ph -> ph.info().command().isPresent() && ph.info().command().get().contains("SomeJavaApp"))
            .forEach((process) -> {
                isRunning.set(true);
            });

    if (isRunning.get()) System.out.println("SomeJavaApp is running already");
   }

Answer 4

The only way I can think of doing it is by invoking a command line application that does the job for you and then screenscraping the output (like Linux's ps and Window's tasklist).

Unfortunately, that'll mean you'll have to write some parsing routines to read the data from both.

Process proc = Runtime.getRuntime().exec ("tasklist.exe");
InputStream procOutput = proc.getInputStream ();
if (0 == proc.waitFor ()) {
    // TODO scan the procOutput for your data
}

Answer 5

YAJSW (Yet Another Java Service Wrapper) looks like it has JNA-based implementations of its org.rzo.yajsw.os.TaskList interface for win32, linux, bsd and solaris and is under an LGPL license. I haven't tried calling this code directly, but YAJSW works really well when I've used it in the past, so you shouldn't have too many worries.

Answer 6

This is my code for a function that gets the tasks and gets their names, also adding them into a list to be accessed from a list. It creates temp files with the data, reads the files and gets the task name with the .exe suffix, and arranges the files to be deleted when the program has exited with System.exit(0), it also hides the processes being used to get the tasks and also java.exe so that the user can't accidentally kill the process that runs the program all together.

private static final DefaultListModel tasks = new DefaultListModel();

public static void getTasks()
{
    new Thread()
    {
        @Override
        public void run()
        {
            try 
            {
                File batchFile = File.createTempFile("batchFile", ".bat");
                File logFile = File.createTempFile("log", ".txt");
                String logFilePath = logFile.getAbsolutePath();
                try (PrintWriter fileCreator = new PrintWriter(batchFile)) 
                {
                    String[] linesToPrint = {"@echo off", "tasklist.exe >>" + logFilePath, "exit"};
                    for(String string:linesToPrint)
                    {
                        fileCreator.println(string);
                    }
                    fileCreator.close();
                }
                int task = Runtime.getRuntime().exec(batchFile.getAbsolutePath()).waitFor();
                if(task == 0)
                {
                    FileReader fileOpener = new FileReader(logFile);
                    try (BufferedReader reader = new BufferedReader(fileOpener))
                    {
                        String line;
                        while(true)
                        {
                            line = reader.readLine();
                            if(line != null)
                            {
                                if(line.endsWith("K"))
                                {
                                    if(line.contains(".exe"))
                                    {
                                        int index = line.lastIndexOf(".exe", line.length());
                                        String taskName = line.substring(0, index + 4);
                                        if(! taskName.equals("tasklist.exe") && ! taskName.equals("cmd.exe") && ! taskName.equals("java.exe"))
                                        {
                                            tasks.addElement(taskName);
                                        }
                                    }
                                }
                            }
                            else
                            {
                                reader.close();
                                break;
                            }
                        }
                    }
                }
                batchFile.deleteOnExit();
                logFile.deleteOnExit();
            } 
            catch (FileNotFoundException ex) 
            {
                Logger.getLogger(Functions.class.getName()).log(Level.SEVERE, null, ex);
            } 
            catch (IOException | InterruptedException ex) 
            {
                Logger.getLogger(Functions.class.getName()).log(Level.SEVERE, null, ex);
            }
            catch (NullPointerException ex)
            {
                // This stops errors from being thrown on an empty line
            }
        }
    }.start();
}

public static void killTask(String taskName)
{
    new Thread()
    {
        @Override
        public void run()
        {
            try 
            {
                Runtime.getRuntime().exec("taskkill.exe /IM " + taskName);
            } 
            catch (IOException ex) 
            {
                Logger.getLogger(Functions.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }.start();
}