Catching unhandled exceptions in Rhino

Question

I'm using Rhino Script Engine and was wondering if it's possible (and how) to register a global handler that could be invoked whenever an unhandled exception is triggered.

I know that I cannot use browser objects like window to register a handler with something like:

window.addEventListener("error", function (e) {
  alert("Error occurred: " + e.error.message);
  return false;
})

Is there an alternative?

Answer 1

Depending exactly what you want -- and exactly what you have -- here's one approach:

var setUncaughtExceptionHandler = function(f) {
	Packages.org.mozilla.javascript.Context.getCurrentContext().setErrorReporter(
		new JavaAdapter(
			Packages.org.mozilla.javascript.ErrorReporter,
			new function() {
				var handle = function(type) {
					return function(message,sourceName,line,lineSource,lineOffset) {
						f({
							type: type,
							message: String(message),
							sourceName: String(sourceName),
							line: line,
							lineSource: String(lineSource),
							lineOffset: lineOffset
						});
					};
				};

				["warning","error","runtimeError"].forEach(function(name) {
					this[name] = handle(name);
				},this);
			}
		)
	);
};

setUncaughtExceptionHandler(function(error) {
	Packages.java.lang.System.err.println("Caught exception: " + JSON.stringify(error,void(0),"    "));
});

var x = true;
var y = null;
var z = y.foo;

The output for this is:

Caught exception: {
    "type": "error",
    "message": "uncaught JavaScript runtime exception: TypeError: Cannot read property \"foo\" from null",
    "sourceName": "null",
    "line": 0,
    "lineSource": "null",
    "lineOffset": 0
}