Getting input and output from a jar file run from java class?

Question

I have a jar file that runs this code:

public class InputOutput {

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        boolean cont = true;
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        while (cont) {
            System.out.print("Input something: ");
            String temp = in.readLine();
            if (temp.equals("end")) {
                cont = false;
                System.out.println("Terminated.");
            }
            else
                System.out.println(temp);
        }
    }
}

I want to program another java class that executes this jar file and can get the input and send output to it. Is it possible? The current code I have is this but it is not working:

public class JarTest {

    /**
     * Test input and output of jar files
     * @author Jack
     */
    public static void main(String[] args) {
        try {
            Process io = Runtime.getRuntime().exec("java -jar InputOutput.jar");
            BufferedReader in = new BufferedReader(new InputStreamReader(io.getInputStream()));
            OutputStreamWriter out = new OutputStreamWriter(io.getOutputStream());
            boolean cont = true;
            BufferedReader consolein = new BufferedReader(new InputStreamReader(System.in));
            while (cont) {
                String temp = consolein.readLine();
                out.write(temp);
                System.out.println(in.readLine());
            }
        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

Thanks for your help

Solution 1

Using Runtime.exec is platform dependent.

If you're using windows try prepending:

cmd /c

to

java -jar .... etc. et

Something like:

...getRuntime().exec("cmd /c java -jar InputOutput.... 

See this also: Make system call and return stdout output.

Solution 2

Do you need to run the jar file in a different process? If not, you can write a Java program that invokes InputOutput.main(). Alternatively, if the name of the jar/class is only known at run-time, you can create a new class-loader, load the said class and invoke main() via reflection.

As for the redirection of input/output streams you can use System.setOut, setIn, setErr.

Solution 3

See also Execute a Java program from our Java program

Comments

[Jack L.]

How would I redirect it in my code using setIn and setOut to get the jar input/output?

[Jack L.]

How would you do this? I am not quite sure I understand. What do I put into a new thread?