Question

I call a class which is located somewhere in a jar file (using java -classpath path/file.jar classname) within my java code.

This work well but only if the command is well formed. If I make a mistake the getRuntime().exect(command) just doesn’t say anything. Bellow I have the working command invocation. I would like to get the error message when the command doesn’t work. If I make a mistake in a cmd (windows) I get a proper error and I can fix it. But not within my java application.

I left a ‘if(input.ready())’ since if I don’t the program freezes when the command line is incorrect. This happens when executing ‘input.readLine()’.

        // Execute a command with an argument that contains a space
        String[] genKOSCommand = new String[] {
                "java",
                "-classpath",
                Config.XDSI_TEST_KIT_HOME + "/xdsitest/lib/xdsitest.jar;"
                        + Config.XDSI_TEST_KIT_HOME + "/xdsitest/classes",
                "ca.etsmtl.ihe.xdsitest.docsource.SimplePublisher", "-k",
                "C:/Softmedical/Viewer_Test/xdsi-testkit-2.0.4/xdsihome/usr/data/image14.dcm" };

        Process child = Runtime.getRuntime().exec(genKOSCommand);

        BufferedReader input = new BufferedReader(new InputStreamReader(
                child.getInputStream()), 13107200);

        String line = null;

        if (input.ready()) {
            while ((line = input.readLine()) != null) {
                System.out.println(line);
            }

            try {
                child.waitFor();
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

Have any advice on how to get an error from the executed command?

Thank you

Answer 1

By using getErrorStream:

BufferedReader errinput = new BufferedReader(new InputStreamReader(
                child.getErrorStream()));

When processing the input from the different streams, it is better to do it in a different thread (since those calls (readLine etc.) are blocking calls.