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https://issues.apache.org/jira/browse/WICKET-6517?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16336698#comment-16336698
]
ASF GitHub Bot commented on WICKET-6517:
----------------------------------------
Github user andruhon commented on the issue:
https://github.com/apache/wicket/pull/256
Another interesting neuance: I didn't find a way to cancel a request before
it was actually sent,
Imagine I do drag and drop of multiple files and jquery uploads them one by
one. Normally with jQuery it is possible to return false from `beforeSend`
handle to cancel the request, however it's not a case with wicket's `bsh`. I
could do something like this:
```JavaScript
Wicket.Ajax.ajax({
u: attrs.u,
m: 'POST',
mp: true,
bsh: [
function (attributes, jqXHR, settings) {
settings.xhr = function () {
try {
if (uploadContext.cancelled) {
// cancel upload
return null;
}
if (uploadContext.item) {
/* Add progress indicator */
xhr.upload.addEventListener("progress",
function (e) {
var progress = Math.round(e.loaded
/ e.total * 100);
onUploadProgress(uploadContext,
attrs, progress);
});
}
return xhr;
} catch (e) {
}
}
}
],
```
However it will cause the jQuery.send to explode with `Cannot read property
'open' of null`
I'm not sure what the best way to do that, but probably `_executeHandlers`
could return false if any of handlers returns false, something like this:
```JavaScript
/**
* A helper function that executes an array of handlers
(before, success, failure)
*
* @param handlers {Array[Function]} - the handlers to execute
* @private
*/
_executeHandlers: function (handlers) {
if (jQuery.isArray(handlers)) {
// cut the handlers argument
var args =
Array.prototype.slice.call(arguments).slice(1);
// assumes that the Ajax attributes is always
the first argument
var attrs = args[0];
var that = this._getTarget(attrs);
for (var i = 0; i < handlers.length; i++) {
var handler = handlers[i];
var r;
if (jQuery.isFunction(handler)) {
r = handler.apply(that, args);
} else {
r = new
Function(handler).apply(that, args);
}
if (r === false) {
return false;
}
}
}
},
//...
```
and
```JavaScript
// execute the request
var jqXHR = jQuery.ajax({
url: url,
type: attrs.m,
context: self,
processData: wwwFormUrlEncoded,
contentType: wwwFormUrlEncoded,
beforeSend: function (jqXHR, settings) {
if(self._executeHandlers(attrs.bsh,
attrs, jqXHR, settings)===false) {
return false;
}
we.publish(topic.AJAX_CALL_BEFORE_SEND,
attrs, jqXHR, settings);
if (attrs.i) {
// show the indicator
Wicket.DOM.showIncrementally(attrs.i);
}
},
// ...
```
> use Ajax for multipart instead of iframe
> ----------------------------------------
>
> Key: WICKET-6517
> URL: https://issues.apache.org/jira/browse/WICKET-6517
> Project: Wicket
> Issue Type: Improvement
> Components: wicket
> Affects Versions: 8.0.0-M8
> Reporter: Sven Meier
> Assignee: Sven Meier
> Priority: Minor
>
> As Andrew Kondratev has pointed out on
> https://github.com/apache/wicket/pull/255, we can use FormData to send
> multipart data via Ajax. This makes the current iframe workaround obsolete.
> Advantages:
> - real Ajax !!1!!!
> - we can drop a lot of code in wicket-ajax-jquery.js
> - users can use Wicket.Ajax to send files as extra parameters, as requested
> in pull request #255
> FormData is supported in Edge and IE 10. I'm not sure whether we still
> support older browsers, but as fallback users can
> - continue using Wicket 7 (supported for the next years)
> - switch to non-Ajax uploads
> - use a polyfill for FormData (several available on github)
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