PrepareAjax Event

A user can add a handler to this event, which will fire before every AJAX request the Documents library makes.

In the case of methods that retrieve elements, such as GetImageElement, this event will fire when an AJAX loading method is used. If an ImageLoader is provided as a parameter, AJAX settings will be retrieved from UrlMode and AjaxOptions. Otherwise, the default options from ElementAjaxMethod and ElementUrlMode are used. See Documents_ImageLoading for more information.

The event data is of type PrepareAjaxEventArgs and will contain the following:

Any changes made to that object will be used in the request. This will allow a user to modify the headers of any request to set authorization headers as they wish for instance.

The following shows how to use PrepareAjax to intercept calls to LoadFromUri and adding custom authentication headers that will be parsed by the server.

Client side JavaScript code:

               // Our interceptor function
               var myPrepareAjaxHandler = function (sender, args) {
                  // Check if this the method we are interested in
                  if (args.sourceClass != "DocumentFactory" || args.sourceMethod != "loadFromUri") {
                     // No
                     return;
                  }
            
                  // Yes, add to the headers. If headers do not exist, intitalize first
                  if (!args.settings.headers) {
                     args.settings.headers = {};
                  }
            
                  args.settings.headers["my_custom_auth_header_key"] = "my_custom_auth_header_val";
               };
            
               // Add our handler to the static PrepareAjax event
               lt.Documents.DocumentFactory.prepareAjax.add(myPrepareAjaxHandler);
            
               // Now call loadFromUri and we should be able to intercept and add our custom headers
               lt.DocumentFactory.loadFromUri(uri, options);
               

Server side .NET code:

               // An Example Of Getting Headers, this could be in FactoryController.cs
               public LoadFromUriResponse LoadFromUri(LoadFromUriRequest request)
               {
                  var headers = Request.Headers;
                  if (headers.Contains("my_custom_auth_header_key"))
                  {
                     var values = headers.GetValues("my_custom_auth_header_key");
                     if (values.Contains("my_custom_auth_header_val"))
                     {
                        // Success, do something ...
                     }
                  }
            
                  // rest of code
               }
               

If the handler aborts the request by setting the value of Cancel to true, then the request will fail immediately and the method will invoke the fail promise. ParseError can be used to obtain extra information on the error and in this situation, the value of IsCancelError will be true.

Reference

DocumentFactory Object
DocumentFactory Members