I am running some java apps and I need to shutdown/close all apps gracefully from windows bat script.
So my question is:
How to invoke shutdown hook by windows bat script and gracefully shutdown java program.
Any suggestion is appreciated.
Thanks in advance.
Take a look at the addShutdownHook method in the Runtime class.
Runtime.getRuntime().addShutdownHook(...);
UPDATE: As per comment below, there is a command TASKKILL in the windows shell that is similar to the *nix kill command. For instance TASKKILL /IM java.exe would terminate all java processes. TASKLIST can be used to find all running processes. Using this in conjunction with a shutdownhook should give you the graceful possibilites required.
A "graceful" shutdown in Java is generally achieved by letting all non-daemon threads complete their work normally. If you have your app listen for a "shutdown" command on some port, then you could have the script trigger the command to that port, which you could then use to set appropriate flags for your threads to stop working, letting the JVM shut down. That's probably the simplest way I've seen it done.
Your .bat script will be a process external to VM. So you will need to implement some kind of IPC in your java application. Some relatively simple options could be using RMI or JMX.
Other possibility is to use some file that can be watched by your application and can be modified by .bat script so other process recognizes that it needs to shutdown.
Related
I work on a Macbook and I would like to close some running applications such as Remote Desktops through using Java.
I'm quite new to programming in Java and other than Google and StackOverflow I'm not sure where to go. I already looked for a solution on Google but all I can find are instruction on how to close Java on Mac OS, not actually how you close a running application through Java code.
So I am looking for some pointers on what Java commands I should use to close a running application in Mac OS. Thank you very much :)
While programming in Java, you only have access to do things inside the JVM. But your code inside the JVM wouldn't usually have permissions to affect other processes running on the operating system.
You can definitely call an external command with something like this:
Process process = Runtime.getRuntime().exec("kill 12345");
That would run the kill command on process id 12345. This would work, assuming you have the right permissions.
You can get more information on the exec command in the docs: https://docs.oracle.com/javase/7/docs/api/java/lang/Runtime.html#exec(java.lang.String)
I've written a very simple command line programme that uses mysqldump to dump data at a specified interval. I wanted it to be running after I run the programme and I disconnect putty ssh connection.
But as soon as I exit the ssh connection, the programme shuts down.
I think I can make my programme run even after I disconnected from the ssh by using daemon threads but I'm worried about not being able to find and stop unnecessary duplicate daemon threads.
The scenario I'm decribing is...
1. I log into the server using putty.
2. Turn on the auto backup programme.
3. I exit the putty connection.
---the daemon is running
4. Hopefully, when I log into the server again, I have a way to stop the auto backup programme if needed.
Cron jobs and DBMS specific methods are out of my options. I'd like to learn how to do the job described above and use it where ever the situation fits not just database backup.
Any good ideas ? : )
In short, you have to launch your program in a special way, and you have (at least) two options: nohup or screen.
Let's now discuss why and how each one works.
nohup
Java's daemon threads is not what you are looking for, they have nothing to do with the issue. You can use normal threads (or even a single-threaded java program). You just need to change the way you launch your java program.
I have many executable jars that run as "daemons" on a bunch of servers, and I made a simple launch script that prepares the environment and makes it possible to terminate the SSH connection without stopping it. The main part is how to invoke the JVM: you use nohup.
nohup java -jar myfile.jar > stdout.log &
From nohup's man,
nohup - run a command immune to hangups, with output to a non-tty
So, when you terminate your SSH connection, it will send SIGHUP to all processes it started which would terminate them as you are observing. With nohup, however, your process is immune to it.
Also, note that I redirect the standard output to a file called stdout.log. This is done so that you can see whatever your program writes to STDOUT (generally some logging information that would be useful for debugging).
To terminate your program, you can use jps to list the PID of your process (say it's 123), then call kill 123. Note that for this to work your program needs to correctly handle this kind of shutdown (which involves adding a shutdown hook with Runtime.getRuntime().addShutdownHook(...) which will terminate all the threads you launched).
If, for whatever reason (a bug, or you didn't implement a graceful shutdown), the program won't terminate after issuing the kill command (which sends the process a SIGTERM), you can change the signal it sends to SIGKILL with kill -9 123, which will simply destroy the process. Mind that this can be as dangerous as a power failure (ie, suppose you are in the middle of the try block of a try {} finally {} -- your finally block will not execute!).
screen
There's an alternative, which is to use SCREEN. With it, you launch a shell that is also immune to shutdowns, and that you can share among many connections. To use it, connect to your server, and then:
screen -R
A new shell will start, in which you run your java program as normal:
java -jar myfile.jar
To make it go to the background, just press ctrl+a ctrl+d. To bring it back to the front, just execute screen -R again. If you wish to terminate your program, you could do so by entering the screen session again and pressing ctrl+c (if your java program correctly deals with this kind of shutdown).
Two possibilities for scheduled tasks, in order from least to most complex, are the TimerTask and the Quartz Scheduler. Both offer the option to cancel/delete the scheduled job.
I have a java program which I start with the comman java -jar MyProgram.jar, and I can stop the java program using the command java -jar MyProgram.jar stop. I am having trouble running my command in the same shell because the previous program is running, is there another way to open another QShell or a way to run another command in the same shell?
Qsh does not support job control, and you can only open one for each session.
The easiest is to open yet another green screen session and run a second qsh inthere
Note that typing SysReq-2 stops the current program, too.
A daemon is presumably intended to be a long-running background service. As such, you would normally be submitting this to run in a some batch subsystem. You would normally use ENDJOB on it from another session.
See your system administrator for details on where they want your job to run on this particular system. There are various options, and testing may be different than how they wish it to run in production.
Is it possible to stop an application in windows using java code ?
I'd like to create a program which is like a shortcut to stop an application on my pc. Is it possible using ProcessBuilder ? Thank you
Plain Java, without native access? No.
ProcessBuilder lets you control processes that you started from within the Java application, but it doesn't give you control to processes that were started by other processes.
As per user988052's comment, you can use pskill from the Sysinternals Suite to accomplish this through Runtime.exec. pskill uses the TerminateProcess function call. You can also call this function with JNI (or some other native caller, like JNA, NLink, etc.), but you'll need to obtain a handle to the process via the OpenProcess function call.
Is it possible to stop an application in windows using java code ? ... Is it possible using ProcessBuilder ?
Only if you launched the application from the same Java application that you are trying to fill it from.
Other than that, you need to resort to running a Windows-specific command to do the killing ... or something based on JNI to make native Windows library calls.
The other complications are that you may not be able to kill certain processes due to permissions issues, and some process may refuse to be killed.
I believe the JRE does not provide an API for system processes. ProcessBuilder can create system processes, but it cannot provide you with a Process object for a process created outside the JVM. I believe that is a philosophical decision on the part of the Java folks, to avoid certain OS-specific tasks where possible. You might think that every OS has pids, or that they all have some kind of kill message, but Java runs on lots of OSes, some of them quite strange.
You could make native code to do it and wrap that with JNI, but that would be wasteful. As Mr 988052 says, I suggest you execute a system-specific command through Runtime.exec or ProcessBuilder. You would need to decide which OSes you want to support, and be sure to get the commands (and the OS-detection code) right for each one.
I am running my java application where i have used threads...
i am running this application using ant command on the terminal..
But when i close my terminal or press ctrl+c,then java program which was running stops...
Please help me out to solve this as i want to run this program continously...
If you kill the Java process, Java will no longer be running. If you want the threads to keep running continuously, the Java program must remain active.
Invoking such a program with ant is not usually the way to do it. On Unix-like systems, you would typically run such a program in the background via /etc/init.d startup scripts. In Windows the equivalent would be starting your program as a service, though I'm not sure of the intricacies involved in getting Java to run this way.
If you're running something from a concole - how about just not killing it and minimising the console? If you're starting it from Linux (or Cygwin) just append a & to the end of the command line and the process will run in the background.
Tell us more about your environment, and what compromises you're prepared to put up with (e.g. having a minimised console window sit in the taskbar) and we can help you more. At the moment, the only definitive answer I can give is that "yes - Ctrl-C will kill your program (as intended). If you want it to keep running, don't tell it to stop running." :-)
You can run your application as a service in linux or windows.
Have a look at the screen command for Linux.
I guess this is desired behavior. If you terminate your application, It gets shut down.
If you wish to run the application in the background you should consider making it a windows service or a deamon.
If you wish to continue running it as a application on *nix, you can consider to use GNU Screen.
Run the ant command in the background and redirect its output to a file:
ant &> my.log &.
NB: this issue does not seems thread related (unless I've misunderstood it).
It sounds like you want to daemonize your ant task. I'd suggest the following command:
nohup ant &> ant.log < /dev/null &
The nohup will allow the program to continue to run after you close the terminal.
I'm surprised nobody has mentioned the all-too-famous Java Service Wrapper. This is an excellent piece of software if you are developing long-running processes (a.k.a services).