24.9. Handling Exceptions

When invoking a remote component method, you can specify an exception handler to process the response in the event of an exception during component invocation. To specify an exception handler function, include a reference to it after the callback parameter in your JavaScript: 
var callback = function(result) { 
    alert(result); 
}; 
var exceptionHandler = function(ex) { 
    alert("An exception occurred: " + ex.getMessage()); 
}; 
Seam.Component.getInstance("helloAction")
    .sayHello(name, callback, exceptionHandler);
If you do not have a callback handler defined, you must specify null in its place: 
var exceptionHandler = function(ex) { 
    alert("An exception occurred: " + ex.getMessage()); 
}; 
Seam.Component.getInstance("helloAction")
    .sayHello(name, null, exceptionHandler);
The exception object that is passed to the exception handler exposes one method, getMessage(), which returns the exception message belonging to the exception thrown by the @WebRemote method.