I’m still learning my way around ASP.NET Web API and have started using Amplify.js in my web apps to consume my web services. I originally learned about Amplify.js from John Papa’s excellent Pluralsight course, “Single Page Apps with HTML5, Web API, Knockout and jQuery”.
Today I noticed that when a server-side error occurs, I was not getting the JSON response that contains the error information in my client-side Amplify error() function (see “Exception Handling in ASP.NET Web API” for an explanation). Taking a look at the Amplify source code revealed that, “out of the box”, Amplify always sends null to the error callback function’s data parameter.
To override this behavior, I created a custom decoder that would use the XHR responseText to feed the error callback data parameter, like so:
amplify.request.decoders.mydecoder =
function (data, status, xhr, success, error) {
if (status === "success") {
success(data, status);
} else if (status === "fail" || status === "error") {
try {
error(JSON.parse(xhr.responseText), status);
} catch(er) {
error(xhr.responseText, status);
}
}
};
Now I’m able to read the Message property and any other information returned from Web API when a server-side exception is thrown.
