Call class, wait for it to exit, call again

Question

I'm working on a program where I want to loop through several config files, and with each file, call a class with that filename as an argument and wait for it to finish. Currently I am doing:

    for (int i = 1; i <= 3; i++){
        String[] a = new String[1];
        a[0] = "data/config" + i + ".xml";
        edu.cwru.sepia.Main2.class.getMethod("main", String[].class).invoke(null, (Object)a);
    }

However, what happens is that the class only gets called once, and then the entire program stops. I think there is an exit line in the class, but since it is a JAR file I can't be sure and I can't edit it.

Let's assume that is the case; how would I get around that to do what I want? i.e. after the invocation ends with the exiting, my outer loop method continues and just calls the class again with the next argument.

Answer 1

If the problem is indeed a System.exit() call in the third-party class, you should be able to work around it by following the recommendation in this answer, which provides the following code:

  private static class ExitTrappedException extends SecurityException { }

  private static void forbidSystemExitCall() {
    final SecurityManager securityManager = new SecurityManager() {
      public void checkPermission( Permission permission ) {
        if( "exitVM".equals( permission.getName() ) ) {
          throw new ExitTrappedException() ;
        }
      }
    } ;
    System.setSecurityManager( securityManager ) ;
  }

  private static void enableSystemExitCall() {
    System.setSecurityManager( null ) ;
  }

However, for your purposes it would likely be a better approach to simply spawn a separate Java process for the third-party application and wait for it to terminate. That way you don't have to worry about the third-party code causing side-effects in your JVM instance, or about trying to guess at how to get rid of the side-effects.