GCViewer CLI doesn't work in headless mode

[ebourg]

GCViewer doesn't work from the command line on a headless system (for example when connecting to a remote server with SSH). The following exception is thrown:

$ java -jar gcviewer-1.36-SNAPSHOT.jar gc.log summary.csv
Exception in thread "main" java.awt.HeadlessException:
No X11 DISPLAY variable was set, but this program performed an operation which requires it.
        at java.desktop/java.awt.GraphicsEnvironment.checkHeadless(GraphicsEnvironment.java:208)
        at java.desktop/java.awt.Window.<init>(Window.java:548)
        at java.desktop/java.awt.Frame.<init>(Frame.java:423)
        at java.desktop/javax.swing.JFrame.<init>(JFrame.java:224)
        at com.tagtraum.perf.gcviewer.view.GCViewerGui.<init>(GCViewerGui.java:29)
        at com.tagtraum.perf.gcviewer.ctrl.impl.GCViewerGuiController.startGui(GCViewerGuiController.java:115)
        at com.tagtraum.perf.gcviewer.GCViewer.doMain(GCViewer.java:83)
        at com.tagtraum.perf.gcviewer.GCViewer.main(GCViewer.java:43)

The command line code should be decoupled from the GUI.

It's possible to work around this issue with xvfb:

$ xvfb-run java -jar gcviewer-1.36-SNAPSHOT.jar gc.log summary.csv