[CONF] Apache Wicket: Calling Wicket from Javascript (page edited)

Tue, 09 Jun 2009 07:12:34 -0700

Page Edited : WICKET : Calling Wicket from _javascript_

Calling Wicket from _javascript_ has been edited by Niels Boeger (Jun 09, 2009).

(View changes)

Content:

This mini tutorial shows you how to call Wicket from _javascript_. It is based on an e-mail from Michael Sparer.

Setting up the Wicket response to the _javascript_ call

Add the AbstractDefaultAjaxBehavior to the component you'd like to call from _javascript_. You then have to override the respond method of AbstractDefaultAjaxBehavior to perform your actions and to append your changes to the response

For example in your panel:

final AbstractDefaultAjaxBehavior behave = new AbstractDefaultAjaxBehavior() {
    protected void respond(final AjaxRequestTarget target) {
        target.add(new Label("foo", "Yeah I was just called from _javascript_!"));
    }
};
add(behave);


Invoking _javascript_ from your Java Wicket component



Any component can add _javascript_ to the page header by implementing IHeaderContributor, that's where the

response-object gets passed.

TODO: add an example of Java code.



Alternatively, you can add a Wicket label containing _javascript_ to your page:


HTML


<script type="text/_javascript_" wicket:id="myScript">/* script will be rendered here */</script>





Java


Label myScript = new Label("myScript", "callWicket();");
myScript.setEscapeModelStrings(false); // do not HTML escape _javascript_ code
add(myScript);





Calling your Java Wicket component from _javascript_


If you add any class that extends AbstractDefaultAjaxBehavior to your page, wicket-ajax.js will be added to the header ofyour web page. wicket-ajax.js provides you with two basic methods to call your component:

function wicketAjaxGet(url, successHandler, failureHandler, precondition, channel) 

and

function wicketAjaxPost(url, body, successHandler, failureHandler, precondition, channel)



Don't POST without POST content


Note that some web servers gulp on HTTP POST requests with no POST content (in other words: "wicketAjaxPost($URL);" is evil).

This is due to some browsers (Firefox, ...) not sending the mandatory header "content-length" when the POST body is empty.

Jetty is generous in this case, while Tomcat might respond with an HTTP 411 error code.

So if you have to use HTTP POST requests, then make sure that at least a dummy _javascript_ object is added as POST data.
 


Here is an example:


_javascript_


function callWicket() {
   var wcall = wicketAjaxGet('$url$' + '$args$', function() { }, function() { });
}


 


'$url$' is obtained from the method behave.getCallbackUrl(). If you paste the String returned from that method into your browser, you'll invoke the respond method, the same applies for the _javascript_ method.



You can optionally add arguments by appending these to the URL string. They take the form &foo=bar.



Obtaining the GET/POST arguments on the server side



Ok, this is actually quite ugly, but you get the optional arguments in the response method like this:


Java


Map map = ((WebRequestCycle) RequestCycle.get()).getRequest().getParameterMap();




Alternatively, you can retrieve a single parameter by its key:


Java


String paramFoo = RequestCycle.get().getRequest().getParameter("foo");

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