One approach is to install a custom repaint manager which detects and logs when painting is performed on a thread other than the EDT. We use this approach on our project, adapted from the following blog: http://weblogs.java.net/blog/alexfromsun/archive/2006/02/debugging_swing.html. This will not detect all classes of EDT thread violations, but it's definitely much better than nothing.
Update:
As a commenter pointed out, the linked web page is no longer available. Here is my code adapted from the blog posting:
import javax.swing.JComponent;
import javax.swing.RepaintManager;
import javax.swing.SwingUtilities;
import org.apache.log4j.Logger;
import sun.awt.AppContext;
public class DetectEdtViolationRepaintManager extends RepaintManager {
private static final Logger LOGGER = Logger.getLogger(
DetectEdtViolationRepaintManager.class);
/**
* Used to ensure we only print a stack trace once per abusing thread. May
* be null if the option is disabled.
*/
private ThreadLocal alreadyWarnedLocal;
/**
* Installs a new instance of DetectEdtViolationRepaintManager which does not
* warn repeatedly, as the current repaint manager.
*/
public static void install() {
install(false);
}
/**
* Installs a new instance of DetectEdtViolationRepaintManager as the current
* repaint manager.
* @param warnRepeatedly whether multiple warnings should be logged for each
* violating thread
*/
public static void install(boolean warnRepeatedly) {
AppContext.getAppContext().put(RepaintManager.class,
new DetectEdtViolationRepaintManager(warnRepeatedly));
LOGGER.info("Installed new DetectEdtViolationRepaintManager");
}
/**
* Creates a new instance of DetectEdtViolationRepaintManager.
* @param warnRepeatedly whether multiple warnings should be logged for each
* violating thread
*/
private DetectEdtViolationRepaintManager(boolean warnRepeatedly) {
if (!warnRepeatedly) {
this.alreadyWarnedLocal = new ThreadLocal();
}
}
/**
* {@inheritDoc}
*/
public synchronized void addInvalidComponent(JComponent component) {
checkThreadViolations();
super.addInvalidComponent(component);
}
/**
* {@inheritDoc}
*/
public synchronized void addDirtyRegion(JComponent component, int x, int y,
int w, int h) {
checkThreadViolations();
super.addDirtyRegion(component, x, y, w, h);
}
/**
* Checks if the calling thread is called in the event dispatch thread.
* If not an exception will be printed to the console.
*/
private void checkThreadViolations() {
if (alreadyWarnedLocal != null && Boolean.TRUE.equals(alreadyWarnedLocal.get())) {
return;
}
if (!SwingUtilities.isEventDispatchThread()) {
if (alreadyWarnedLocal != null) {
alreadyWarnedLocal.set(Boolean.TRUE);
}
LOGGER.warn("painting on non-EDT thread", new Exception());
}
}
}
