Hi,
I have implemented a "trappable command", that will show a popup in
case of an uncaught exception during its execution. It seems that a
stack trace is not available using the normal Java methods - at least
not when run in a browser. Any suggestions?
Here's the code.
/**
* Implement the execute method for a command that will have a
reasonable
* way to handle thrown exceptions.
*/
public abstract class TrappableCommand implements Command {
/**
* Execute this command, report any exception in a popup panel.
*/
public void execute() {
execute(this);
}
/**
* Execute the provided command, report any exception in a popup
panel.
* @param cmd The command to execute.
*/
public static void execute(final TrappableCommand cmd) {
try {
cmd.executeWithCatch();
} catch (final Throwable t) {
final PopupPanel panel = new PopupPanel(true);
panel.setWidget(makeWidget(t));
panel.center();
}
}
/**
* Make a normal command trappable.
*
* @param cmd The command to make trappable.
* @return A trappable wrapper for cmd.
*/
public static Command makeTrappable(final Command cmd) {
return new TrappableCommand() {
@Override
protected void executeWithCatch() {
cmd.execute();
}};
}
private static Widget makeWidget(final Throwable t) {
final VerticalPanel host = new VerticalPanel();
host.add(LabelFactory.makeNewLabelBiggest("Exception
caught"));
addThrowable(t, host);
return host; }
private static void addThrowable(final Throwable t, final
VerticalPanel host) {
host.add(new Label("Class: " + t.getClass().getName()));
host.add(new Label("Message:"));
addStringWithLinebreaks(host, t.getMessage());
host.add(new Label("Stacktrace:"));
addWithLinebreaks(host, t.getStackTrace());
if (t.getCause() != null) {
host.add(LabelFactory.makeNewLabelBig("Caused by"));
addThrowable(t.getCause(), host);
} else {
host.add(new Label("No cause"));
}
}
private static void addWithLinebreaks(VerticalPanel host,
StackTraceElement[] stackTrace) {
if (stackTrace.length == 0) {
host.add(new Label("No stacktrace"));
} else {
for (StackTraceElement item : stackTrace) {
host.add(new Label(item.toString()));
}
}
}
private static void addStringWithLinebreaks(VerticalPanel host,
String s) {
String strings[] = s.split("\n");
for (String str : strings) {
host.add(new Label(str));
}
}
/**
* Implement to add behavior.
*/
protected abstract void executeWithCatch() ;
}
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