Hi Adam
I've finally worked it out and a lot of it is very much down to your
help!!
What I wasn't reading on Dan's article was a very important part of
his Python server, basically the line:
body = '%s(%s);' % (fun_name, file('json.js').read())
which as you quite rightly stated includes the damn function name and
is very important!!!
So I have taken your advice and implemented my client side code as per
Dans article:
============
public void makeCall(String number)
{
String serverURL = ClientGlobals.CALL_SERVICE_URL+"callback=";
String callbackName = reserveCallback();
setup(this, callbackName);
System.out.println(serverURL + callbackName);
System.out.println(callbackName);
addScript(callbackName, serverURL + callbackName);
}
public String reserveCallback()
{
while (true)
{
if (!callbacks.containsKey(new Integer(curIndex)))
{
callbacks.put(new Integer(curIndex), null);
return "__gwt_callback" + curIndex++;
}
}
}
/**
* <p>Adds the JSONP script to our widget so we can make XSS requests
baby</p>
*
* @param uniqueId The unique id of the call
* @param url The URL of our Request
*/
public void addScript(String uniqueId, String url)
{
Element e = DOM.createElement("script");
DOM.setElementAttribute(e, "language", "JavaScript");
DOM.setElementAttribute(e, "src", url);
scriptTags.put(uniqueId, e);
DOM.appendChild(RootPanel.get().getElement(), e);
}
public void handle(JavaScriptObject jso)
{
if( jso != null )
{
Window.alert("Woohoo JSO is not null it bloody worked");
}
}
/**
*
* <p>Sets up our Javascript cross site JSON call</p>
*
* @param model Handles our Cross Site JSON call
* @param callback
*/
public native static void setup(CallModel model, String callback)
/*-{
$wnd[callback] = function(someData)
{
[EMAIL PROTECTED]::handle(Lcom/google/gwt/core/client/
JavaScriptObject;)(someData);
}
}-*/;
============
Then importantly in my server side I have used the callback name in my
JSON output as you quite rightly mention!! :)
protected void doPost(HttpServletRequest req, HttpServletResponse
resp) throws ServletException, IOException
{
String asyncCallback = req.getParameter("callback");
String output = asyncCallback+"([{color: \"red\",value: \"#f00\"}])";
resp.setContentType("text/javascript");
resp.addHeader("Pragma", "no-cache");
resp.setStatus(200);
PrintWriter out = resp.getWriter();
out.println(output);
}
And its not hitting my handler
Thank you very much for your help. I'm going to post a tutorial on my
blog http://eggsylife.blogspot.com and will credit help toward
yourself.
Eggsy
On Oct 7, 1:10 pm, eggsy84 <[EMAIL PROTECTED]> wrote:
> Hi Adam
>
> Thank you for this insight - I'll use Dans code for my client side to
> fix this and add the callback as a parameter!
>
> Thank you for all your help! I'll let you know how I get on
>
> Regards,
>
> On Oct 7, 1:03 pm, Adam T <[EMAIL PROTECTED]> wrote:
>
> > mmm, your code below doesn't really follow the pattern in the link of
> > your first post - however, I think I know why your handle method is
> > calling. The code below seems to use a timer to loop around checking
> > if something has been returned, if not it fires your handler with null
> > - which explains why you handler is called and you only see null. I
> > assume that if you add the method name to your response you would
> > eventually get your handler called with a value.
>
> > I might misunderstand the code on the web site you link to, but I
> > personally would recommend using the code shown in Dan's article
> > (http://code.google.com/support/bin/answer.py?
> > answer=65632&topic=11368 ) for the client side. It works fine,
> > removes the need for a timer (which is going to take resource in your
> > application) and truly handles the asynchronous nature of the web.
>
> > //Adam
>
> > On 7 Okt, 13:46, eggsy84 <[EMAIL PROTECTED]> wrote:
>
> > > I expect thats what I'm missing then!
>
> > > My calling method is as follows:
>
> > > public native static void getJson(int requestId, String url, CallModel
> > > handler)
> > > /*-{
> > > var callback = "callback" + requestId;
>
> > > var script = document.createElement("script");
> > > script.setAttribute("src", url+callback);
> > > script.setAttribute("type", "text/javascript");
>
> > > window[callback] = function(jsonObj)
> > > {
> > > [EMAIL PROTECTED]::handleJsonResponse(Lcom/google/
> > > gwt/core/client/JavaScriptObject;)(jsonObj);
> > > window[callback + "done"] = true;
> > > }
>
> > > // JSON download has 1-second timeout
> > > setTimeout(function()
> > > {
> > > if (!window[callback + "done"])
> > > {
> > > [EMAIL PROTECTED]::handleJsonResponse(Lcom/
> > > google/gwt/core/client/JavaScriptObject;)(null);
> > > }
>
> > > // cleanup
> > > document.body.removeChild(script);
> > > delete window[callback];
> > > delete window[callback + "done"];
> > > }
> > > , 1000);
>
> > > document.body.appendChild(script);
>
> > > }-*/;
>
> > > I have adapted it from a useful guide here:
>
> > >http://giantflyingsaucer.com/blog/?p=126
>
> > > Eggsy
>
> > > On Oct 7, 12:24 pm, Adam T <[EMAIL PROTECTED]> wrote:
>
> > > > I think what you are missing is the function name in your output from
> > > > the servlet. From what I see, you just return:
>
> > > > [{color: \"red\",value: \"#f00\"}]
>
> > > > when I would expect a response something like:
>
> > > > mycallback([{color: \"red\",value: \"#f00\"}])
>
> > > > where the "mycallback" is the name of the function you add to the DOM
> > > > which calls your handleJSONResponse method - without returning a
> > > > function from your servlet, I'm not sure how your handle method is
> > > > being called.
>
> > > > Also, are you defining your callback code to pick up the parameter,
> > > > e.g.
>
> > > > public native static void setup(YourHandlerClass h, String callback) /
> > > > *-{
> > > > window[callback] = function(someData) {
> > > > [EMAIL PROTECTED]::handleJSONResponse(Lcom/
> > > > google/gwt/core/client/JavaScriptObject;)(someData);
> > > > }
> > > > }-*/;
>
> > > > without the (Lcom/google/gwt/core/client/JavaScriptObject;)(someData)
> > > > part it won't pick up the returned data
>
> > > > //Adam
>
> > > > On 7 Okt, 10:14, eggsy84 <[EMAIL PROTECTED]> wrote:
>
> > > > > Hi Adam,
>
> > > > > Thank you for the reply it definately helps! when you say it needs to
> > > > > be well-formed javascript I have implemented a method that performs
> > > > > the following:
>
> > > > > /* (non-Javadoc)
> > > > > * @see
> > > > > javax.servlet.http.HttpServlet#doPost(javax.servlet.http.HttpServletRequest,
> > > > > javax.servlet.http.HttpServletResponse)
> > > > > */
> > > > > @Override
> > > > > protected void doPost(HttpServletRequest req, HttpServletResponse
> > > > > resp) throws ServletException, IOException
> > > > > {
> > > > > String output ="[{color: \"red\",value: \"#f00\"}]";
> > > > > resp.setContentType("text/javascript");
> > > > > resp.addHeader("Pragma", "no-cache");
> > > > > resp.setStatus(200);
> > > > > PrintWriter out = resp.getWriter();
> > > > > out.println(output);
>
> > > > > }
>
> > > > > Would that be sufficient? Well I ask the question but I assume not as
> > > > > with my implementation I successfully go back to my client handle
> > > > > method now but the JavascriptObject passed in is always null.
>
> > > > > My client side handle method is very basic as a test (shown below) and
> > > > > I can confirm that when the claa is complete is definately hits this
> > > > > method so the glue between is wrong somehow?
>
> > > > > public void handleJsonResponse(JavaScriptObject jso)
> > > > > {
> > > > > if (jso == null)
> > > > > {
> > > > > Window.alert("Unable to parse JSON");
> > > > > return;
> > > > > }
> > > > > else
> > > > > {
> > > > > Window.alert("Well done Woohoo!!");
> > > > > }
>
> > > > > }
>
> > > > > eggsy
>
> > > > > On Oct 6, 9:28 pm, Adam T <[EMAIL PROTECTED]> wrote:
>
> > > > > > Eggsy,
>
> > > > > > To get it to work you need to get the plumbing right, and it's not
> > > > > > quite the same way as calling from code - btw, the example on that
> > > > > > page is aimed at client side not server side. The server is any
> > > > > > language you want as long as it returns a well-formed JavaScript
> > > > > > segment of the form:
>
> > > > > > mycallback({....some json content....})
>
> > > > > > So your servlet would work as long as it returns something like the
> > > > > > above.
>
> > > > > > In this approach you don't call the servlet in the normal way from
> > > > > > the
> > > > > > program code, rather it gets called as a consequence of adding a
> > > > > > <script> tag to the DOM - this is what the addScript() method in the
> > > > > > example code does. Once the script is added to the DOM the browser
> > > > > > accesses the defined url of your service and expects a response. As
> > > > > > the response is a JavaScript function, it will get evaluated in the
> > > > > > browser.
>
> > > > > > If you also define a function in the DOM with the same name you
> > > > > > expect
> > > > > > back in the server response, e.g. mycallback, and that function
> > > > > > calls
> > > > > > the GWT handle() function then the loop is closed. The example code
> > > > > > adds such a function using the setUp() method.
>
> > > > > > The example code reserves a new function name for each "call" made
> > > > > > to
> > > > > > the server, adds that new function to the DOM and then the <script>
> > > > > > tag.
>
> > > > > > Where things usually go wrong are if the server returns a function
> > > > > > name not set up, or the response is not a valid javascript
> > > > > > expression.
>
> > > > > > Hope that helps in some small way!
>
> > > > > > //Adam
>
> > > > > > this then gets evaluated in the browser
>
> > > > > > On 6 Okt, 17:02, eggsy84 <[EMAIL PROTECTED]> wrote:
>
> > > > > > > Hi all,
>
> > > > > > > Taking the informative article by Dan Morrill at GWT
>
> > > > > > > Link:http://code.google.com/support/bin/answer.py?answer=65632&topic=11368
>
> > > > > > > It explains how to code for Server side mashups so that you can
> > > > > > > perform cross site JSONP calls.
>
> > > > > > > In the article he uses the handle method (Shown below) to handle
> > > > > > > the
> > > > > > > return from the server side:
>
> > > > > > > public void handle(JavaScriptObject jso) {
> > > > > > > JSONObject json = new JSONObject(jso);
> > > > > > > JSONArray ary =
> > > > > > > json.get("feed").isObject().get("entry").isArray();
> > > > > > > for (int i = 0; i < ary.size(); ++i) {
> > > > > > > RootPanel.get().add(new
> > > > > > > Label(ary.get(i).isObject().get("title").isObject().get("$t").toString()));
> > > > > > > }
> > > > > > > }
>
> > > > > > > I have tried writing my own basic Java Servlet GET/POST we all
> > > > > > > know
> > > > > > > the score and I can successfully call into my servlet but I never
> > > > > > > get
> > > > > > > back to my client side, in this case after the servlet has done
> > > > > > > its
> > > > > > > stuff, I never go back to the handle method to perform some whizz
> > > > > > > bang
> > > > > > > GWT stuff - is there something specific you are required to do on
> > > > > > > the
> > > > > > > server side? Such as extends RemoteServiceServlet as you would do
> > > > > > > in a
> > > > > > > normal GWT AsyncCallback call? Anyone got any ideas?
>
> > > > > > > Thanks all
>
> > > > > > > eggsy
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