How to run a java GUI on mac osx after ssh

Question

I am using java 1.7.0_67 on mac osx 10.7.5. Here is my hello world gui:

import javax.swing.*; 
import java.awt.*; 
import java.awt.event.*; 

public class helloWorld extends JFrame {
    helloWorld(String title) { 
        this.setSize(500,500); 
        setTitle(title); 
    }

    public static void main(String[] args) {
       helloWorld window = new helloWorld("Helloworld");
       window.setVisible(true);
       window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    }
}

This runs just fine when i open a mac terminal and type java helloWorld. However, when I ssh into my mac from another host, set my DISPLAY env variable, and run, I get the following exception:

Exception in thread "main" java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
    at java.awt.GraphicsEnvironment.checkedHeadless(GraphicsEnvironment.java:207)
    at java.awt.Window.<init>(Window.java:535)
    at java.awt.Frame.<init>(Frame.java:420)
    at java.awt.Frame.<init>(Frame.java:385)
    at javax.swing.JFrame.<init>(JFrame.java:180)
    at helloWorld.<init>(helloWorld.java:8)
    at helloWorld.main(helloWorld.java:14)

This used to work on Java 1.6, from what I've been able to research this appears to be a purposeful break.

Any ideas how I can get my gui to display after ssh-ing in from a remote host? I don't want to use X11 (would prefer native gui rendering).

Answer 1

The Java developers chose to use the headless Toolkit when running in an ssh session on Mac OS X. You can convince Java to go ahead and display the GUI anyway by setting the AWT_TOOLKIT environment variable to CToolkit. For example, in bash:

export AWT_TOOLKIT=CToolkit
java helloWorld

With the variable set, your GUI should display as you expect.