Javascript – Air XmlHttpRequest time out if remote server is offline

airjavascriptxmlhttprequest

I'm writing an AIR application that communicates with a server via XmlHttpRequest.

The problem that I'm having is that if the server is unreachable, my asynchronous XmlHttpRequest never seems to fail. My onreadystatechange handler detects the OPENED state, but nothing else.

Is there a way to make the XmlHttpRequest time out?

Do I have to do something silly like using setTimeout() to wait a while then abort() if the connection isn't established?

Edit:
Found this, but in my testing, wrapping my xmlhttprequest.send() in a try/catch block or setting a value on xmlhttprequest.timeout (or TimeOut or timeOut) doesn't have any affect.

Best Answer

With AIR, as with XHR elsewhere, you have to set a timer in JavaScript to detect connection timeouts.

var xhReq = createXMLHttpRequest();
xhReq.open("get", "infiniteLoop.phtml", true); // Server stuck in a loop.

var requestTimer = setTimeout(function() {
   xhReq.abort();
   // Handle timeout situation, e.g. Retry or inform user.
}, MAXIMUM_WAITING_TIME);

xhReq.onreadystatechange = function() {
  if (xhReq.readyState != 4)  { return; }
  clearTimeout(requestTimer);
  if (xhReq.status != 200)  {
    // Handle error, e.g. Display error message on page
    return;
  }
  var serverResponse = xhReq.responseText;  
};

Source

Related Solutions

Javascript – Alternatives for Javascript Synchronous XMLHttpRequest (as timing out in Safari)

Generally, you'll want to stick to asynchronous requests, as they're non-blocking. And with them, you'll want to use a callback -- or, simply, a function that is setup to be called later.

You can set the callback with the onreadystatechange property of an XMLHttpRequest:

xhr.onreadystatechange = function () {
    if (xhr.readyState === 4) {   // DONE
        if (xhr.status === 200) { // OK
            handleSuccess(xhr);
        } else {
            handleError(xhr);
        }
    }
};

As the property name suggests, it will be called as the value of readyState changes, where a value of 4 means the request has completed (successful or not).

You'd then handle your sorting, filtering, etc. within another function -- in this example, handleSuccess.

You can also benefit from using any of a number of existing libraries -- e.g., jQuery (1.6 or later for this snippet):

$.get('/web/service/request')
    .done(function (result) {
        // sorting, filtering, etc
    })
    .fail(function (xhr) {
        // error notification, etc.
    });

Javascript – Intercept XMLHttpRequest and modify responseText

//
// firefox, ie8+ 
//
var accessor = Object.getOwnPropertyDescriptor(XMLHttpRequest.prototype, 'responseText');

Object.defineProperty(XMLHttpRequest.prototype, 'responseText', {
	get: function() {
		console.log('get responseText');
		return accessor.get.call(this);
	},
	set: function(str) {
		console.log('set responseText: %s', str);
		//return accessor.set.call(this, str);
	},
	configurable: true
});


//
// chrome, safari (accessor == null)
//
var rawOpen = XMLHttpRequest.prototype.open;

XMLHttpRequest.prototype.open = function() {
	if (!this._hooked) {
		this._hooked = true;
		setupHook(this);
	}
	rawOpen.apply(this, arguments);
}

function setupHook(xhr) {
	function getter() {
		console.log('get responseText');

		delete xhr.responseText;
		var ret = xhr.responseText;
		setup();
		return ret;
	}

	function setter(str) {
		console.log('set responseText: %s', str);
	}

	function setup() {
		Object.defineProperty(xhr, 'responseText', {
			get: getter,
			set: setter,
			configurable: true
		});
	}
	setup();
}

Best Answer

Related Solutions

Javascript – Alternatives for Javascript Synchronous XMLHttpRequest (as timing out in Safari)

Javascript – Intercept XMLHttpRequest and modify responseText

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