Console application executing from Java

[Imre Tokai]

Hello!


I'm executing a C++ application that contains GUI from Java via Runtime.getRuntime().exec( cmd ), and it's working properly.
When I want to execute C++ console application it doesn't seem to return information that it's finished and remains to hang.
Even C++ code part behaved as expected.

Here is the whole example:

   

import javax.swing.JTextField;
import javax.swing.JTextArea;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JButton;
import javax.swing.JScrollPane;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.Container;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
public class ExecTester
{
	JTextField commandField;
	JTextArea outputText;
	static Process pr;

public void showUI()
{
JFrame frame = new JFrame("Runtime.exec() Tester");

// frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
// Sun docs say use JFrame.EXIT_ON_CLOSE, but it doesn't exist,
// (in JDK 1.2, at least) so I'll add this window adapter:
frame.addWindowListener( new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
	try {
		System.out.println( "Closing...: " + pr.waitFor() );
	} catch (InterruptedException e1) {
		// TODO Auto-generated catch block
		e1.printStackTrace();
	}
System.exit(0);
}
}
);

Container pane = frame.getContentPane();
pane.setLayout( new java.awt.FlowLayout() );

pane.add(new JLabel("Enter your command:"));

commandField = new JTextField("notepad c:\\windows\\win.ini", 30);
pane.add(commandField);

final JButton goButton = new JButton("Execute It!");
pane.add(goButton);

goButton.addActionListener( new goButtonListener() );

pane.add( new JLabel( "Results of execution:" ) );
outputText = new JTextArea(5,50);
pane.add( new JScrollPane(outputText) );

frame.pack();
frame.setSize( 600, 200 );

frame.setVisible(true);
}

class goButtonListener implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
outputText.append( runExec( commandField.getText() ) );
}
}

public static String runExec( String cmd )
{
String results = "Results of Runtime.getRuntime().exec( \"" +
cmd + "\" ):";

try
{
  pr = Runtime.getRuntime().exec( cmd );
results += " No problem.";
}
catch( java.io.IOException e )
{
results += "\n " + e.toString();
}

return results + "\n";
}


public static void main( String[] args )
{
if( args.length == 0 || args[0].equals( "/showui" ) )
(new ExecTester()).showUI();
else
System.out.println( "Runtime.getRuntime().exec( \"" +
args[0] + "\" ): " + runExec(args[0]));
}
}

 

How to call the C++ console application from Java properly, with notification that will avoid hanging?


Regards

[Ulf Dittmer]

I don't see any code that would handle the process' input, output and error streams. Read and follow the article "When Runtime.exec() doesn't" by Daconta; it explains all this.