A quick Google search give plenty answers using a simple :
Runtime.getRuntime().exec("java -jar myApp.jar"); System.exit(0);
This indeed basically works, but this answer that does not convince me for several reasons :
1) What about VM and program arguments ? (this one is secondary in fact, because can be solve it quite easily).
2) What if the main is not a jar (which is usually the case when launching from an IDE) ?
3) Most of all, what about the cleaning of the closing application ? For example if the application save some properties when closing, commit some stuffs etc.
4) We need to change the command line in the code source every time we change a parameter, the name of the jar, etc.
Overall, something that works fine for some test, sandbox use, but not a generic and elegant way in my humble opinion.
Ok, so my purpose here is to implement a method :
public static void restartApplication(Runnable runBeforeRestart) throws IOException { ... }
that could be wrapped in some jar library, and could be called, without any code modification, by any Java program, and by solving the 4 points raised previously.
Let's start by looking at each point and find a way to answer them in an elegant way (let's say the most elegant way that I found).
1) How to get the program and VM arguments ? Pretty simple, by calling a :
ManagementFactory.getRuntimeMXBean().getInputArguments();
Concerning the program arguments, the Java property sun.java.command we'll give us both the main class (or jar) and the program arguments, and both will be useful.
String[] mainCommand = System.getProperty("sun.java.command").split(" ");
2) First retrieve the java bin executable given by the java.home property :
String java = System.getProperty("java.home") + "/bin/java";
The simple case is when the application is launched from a jar. The jar name is given by a mainCommand[0], and it is in the current path, so we just have to append the application parameters mainCommand[1..n] with a -jar to get the command to execute :
String cmd = java + vmArgsOneLine + "-jar " + new File(mainCommand[0]).getPath() + mainCommand[1..n];
We'll suppose here that the Manifest of the jar is well done, and we don't need to specify either the main nor the classpath.
Second case : when the application is launched from a class. In this case, we'll specify the class path and the main class :
String cmd = java + vmArgsOneLine + "-cp \"" + System.getProperty("java.class.path") + "\" " + mainCommand[0] + mainCommand[1..n];
3) Third point, cleaning the old application before launching the new one.
To do such a trick, we'll just execute the Runtime.getRuntime().exec(cmd) in a shutdown hook.
This way, we'll be sure that everything will be properly clean up before creating the new application instance.
Runtime.getRuntime().addShutdownHook(new Thread() { @Override public void run() { ... } });
Run the runBeforeRestart that contains some custom code that we want to be executed before restarting the application :
if(beforeRestart != null) { beforeRestart.run(); }
And finally, call the
System.exit(0);
And we're done. Here is our generic method :
/** * Restart the current Java application * @param runBeforeRestart some custom code to be run before restarting * @throws IOException */ public static void restartApplication(Runnable runBeforeRestart) throws IOException { try { // java binary String java = System.getProperty("java.home") + "/bin/java"; // vm arguments List<String> vmArguments = ManagementFactory.getRuntimeMXBean().getInputArguments(); StringBuffer vmArgsOneLine = new StringBuffer(); for (String arg : vmArguments) { // if it's the agent argument : we ignore it otherwise the // address of the old application and the new one will be in conflict if (!arg.contains("-agentlib")) { vmArgsOneLine.append(arg); vmArgsOneLine.append(" "); } } // init the command to execute, add the vm args final StringBuffer cmd = new StringBuffer("\"" + java + "\" " + vmArgsOneLine); // program main and program arguments (be careful a sun property. might not be supported by all JVM) String[] mainCommand = System.getProperty("sun.java.command").split(" "); // program main is a jar if (mainCommand[0].endsWith(".jar")) { // if it's a jar, add -jar mainJar cmd.append("-jar " + new File(mainCommand[0]).getPath()); } else { // else it's a .class, add the classpath and mainClass cmd.append("-cp \"" + System.getProperty("java.class.path") + "\" " + mainCommand[0]); } // finally add program arguments for (int i = 1; i < mainCommand.length; i++) { cmd.append(" "); cmd.append(mainCommand[i]); } // execute the command in a shutdown hook, to be sure that all the // resources have been disposed before restarting the application Runtime.getRuntime().addShutdownHook(new Thread() { @Override public void run() { try { Runtime.getRuntime().exec(cmd.toString()); } catch (IOException e) { e.printStackTrace(); } } }); // execute some custom code before restarting if (beforeRestart != null) { beforeRestart.run(); } // exit System.exit(0); } catch (Exception e) { // something went wrong throw new IOException("Error while trying to restart the application", e); } }
Thanks a lot! Just came across this, works like charm!
ReplyDeletenice tutorial... how do I call this application from a class please.
ReplyDeletevery nicely explained tutorial. But how to invoke this application from my class?
ReplyDeleteCan anybody please reply to above request??
ReplyDeleteWow, I guess I came in the perfect moment haha, JK.
ReplyDeleteJust you have to treat like a simple java method, I mean, just put it into a java class and wherever you are just make a instance of that class and call the method (restartApplication()). In the parameter you can write null if you don't have any code that you want to execute before the restarting of the application.
It works for me perfectly.
Regards :D
Thanks!! it worked i just passed null in the parameters after creating an instance and surrounding with try catch and it ran.
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Not working when we are usung web start jnlp file.
ReplyDeletePlease suggest if have any idea .
Thanks
You can tak a look how we restart JOSM, it's working with WebStart too: https://josm.openstreetmap.de/browser/trunk/src/org/openstreetmap/josm/actions/RestartAction.java
Deleteperde modelleri
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Nice blog.
ReplyDeleteThanks for sharing.
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