Runtime.exec() causes app to hang

Question

Hello all, I'm having an issue with the Runtime.exec() and I'm hoping someone in the forum can shed some light on it for me.
My application currently includes the capability for my end users to run a variety of reports, all of which are written in SQR (BRIO reporting language). Since my application is in Java ( and all the reports were written for a previous application), I use the Runtime.exec() call to launch the SQR viewer application. The problem I'm having is this: When I run the code below in my development environment (using a front end framework from Oracle (JDeveloper)), everything works fine. When I deploy my application to a jar file, the application runs fine until the code below is called. At this point the application hangs terribly and my CPU usage is maxed out by my app. The process for the report is created but is unable to garner the necessary resources to run because my application is using them all. If I kill my application, the report process then runs as expected.
Why would the same code run fine in development but not when deployed to a jar file?
The following is the code in question:
    try {
      Runtime rt = Runtime.getRuntime();
      Process proc = rt.exec(sDrive + "\\SQR6\\SQRW " + sDrive + "\\SQR6\\REPORTS\\" + repName + ".SQT " + sConn + " -RT -FC:\\SPL\\ -C -ZIV");
      InputStream stderr = proc.getErrorStream();
      InputStreamReader isr = new InputStreamReader(stderr);
      BufferedReader br = new BufferedReader(isr);
      String line = null;
      while ( (line = br.readLine()) != null)
        System.out.println(line);
      int exitVal = proc.waitFor();
    catch (Throwable ie)
      ie.printStackTrace();
    }    All thoughts and suggestions are welcomed.
Thanx in advance,
eribs4e

Answer 1

So you either tried adding a reader for stdout, or you're sure that nothing is produced on stdout? And you're sure it's not expecting anything on stdin?
You say your app runs fine up to that code, and then eats all the CPU right? Sounds like a spin lock. One possibility is that it's something like this: br = bufferedReaderForStdOut;
while ( (line = br.readLine()) != null)
        System.out.println(line);
while ((line = br.readLine() == null); Not that I expect that you have precisely that in your code, but I suspect the problem may actually be a spin-lock that precedes the code you've posted. I don't see anything obviously wrong with what you have, so if there's a problem in your code, it's probably in what you haven't shown.