How do I launch a new Java app from a running Java app?

How do I launch a new Java app from a running Java app?

Post by steve.albi » Sat, 30 Dec 2006 03:57:28


Here is the motivation for my question. I have a Swing-based
application that is launched using Web Start. I would like this
application to launch other application instances using it's own
classpath (e.g. fork new instances of itself) when the user invokes
certain functions.

I know that I can use Runtime or ProcessBuilder to launch another Java
application. If I use this approach, how can I get the current
application's classpath so that I can pass it as an argument to the
Java sub process?

Sincerely,
Steve A
 
 
 

How do I launch a new Java app from a running Java app?

Post by stev » Thu, 04 Jan 2007 17:56:54

On Fri, 29 Dec 2006 02:57:28 +0800, XXXX@XXXXX.COM wrote
(in article < XXXX@XXXXX.COM >):


The following segment works on windows/mac & linux and has been in use for
over 2 years in our office


Fairly easily, basically I use it for deploying updates.
I have a class called "bootloader" that contains the following, the most
important thin is that your "bootloader" class MUST NOT link into any of
your other libraries. (if it does then the JVM goes on a class hunt trying to
resolve all other classes & preload them)

That allows you to use the bootloader to auto update any other files , other
than "bootloader"




OurJarClassPathArray, holds that paths of any jars you may need (libraries,
DO NOT HARDCODE, or use imports)

loadThisClass , holds the class you want to run

final Method mainMethod;
final Class toRun;

ClassLoader loader = new URLClassLoader(OurJarClassPathArray);
toRun = loader.loadClass(loadThisClass);
mainMethod = findMain(toRun, thisargs);

if ((mainMethod != null)) {
//launch the new program in a new thread so we can exit the
bootloader (can we really?)
mainThread =
new Runnable() {
public void run() {
try {
final String[] dummy = null;
mainMethod.invoke(null,
new Object[] { dummy });
} catch (Exception e) {
System.out.println(
"Exception Caused when trying to
Execute main Class");
e.printStackTrace();
}
}
};
//this appears to be important code that was stopping
the shit
//running on the linux correctly, specifically the
classloader.
Thread mainRunner=new Thread(mainThread);
mainRunner.setContextClassLoader(loader );
mainRunner.start();
System.out.println("We think have exited the BootLoader ");
System.gc();

 
 
 

How do I launch a new Java app from a running Java app?

Post by Andrew Tho » Thu, 04 Jan 2007 19:04:09


Why not instantiate the new instance directly
from the code in the original instance? E.G.

class Application {
...
public void actionPerformed(ActionEvent ae) {
if (...) {
Application app = new Application();
} else if ....

Andrew T.
 
 
 

How do I launch a new Java app from a running Java app?

Post by Daniel Pit » Fri, 05 Jan 2007 01:59:31


Or even better...

public void actionPerformed(ActionEvent ae) {
if (shouldSpawnNewApp) {
Thread thread = new Thread() {
public void run() {
MyMainClass.main(new String[] {} );
}
};
thread.setPriority(Thread.NORM_PRIORITY);
thread.start();
}
}