This technique only works for JSON that is returned as a valid
JavaScript function, it will not work for XML. It relies on the fact
that the returned JavaScript expression is evaluated by the browser
and thus your handle function is called. Without that, your handle
function can never be called with a JavaScriptObject that contains
data.
Normally you can get Google APIs as JSON by adding alt=json as a
parameter to the call, but it doesn't seem to work for the weather.
To handle only XML you will have to go through a proxy server, i.e.
your application makes a call to your server, your server makes a call
to weather service and the returned data is fed back to your
application by your server.
For completeness, you get "null" because that is exactly what your
code is telling it to send. As you are not getting a valid JSON
string wraped in JavaScript function then the browser never gets to
call your handle function with data, and you will always execute the
code in the timeout section. That code in the timeout section always
make this call:
[EMAIL PROTECTED]::handleXmlResponse
(Lcom/google/gwt/core/client/JavaScriptObject;Lfarmapp/client/weather/
WeatherReportCallback;)(null, reportCallback);
where the first parameter is "null", and hence your handle function is
always trying to handle "null".
Hope that goes someway to helping/explaining!
//Adam
9 Dec, 05:55, Ryan <[EMAIL PROTECTED]> wrote:
> Hello,
>
> I am trying to access an XML feed via a URL request of an external
> server, but of course am restricted by the browser SOP. So I tried to
> follow the example given in the Getting Started guide for getting
> around SOP on a JSON request, "Get JSON via HTTP", hoping to adapt it
> for XML. But it's not working. The JSNI procedure getXml will return
> to handleXmlResponse, as it is supposed to, but the JavaScriptObject
> param xml is always null. It seems as though the request is timing
> out, as increasing the timeout delay in the JSNI procedure seems to
> have an effect. I have increased it all the way to 30 seconds hoping
> for a response, but it's just not coming.
>
> Obviously the procedure for XML is different enough that I need
> further modifications. Can anyone help me out? Thanks!
>
> Ryan
>
> **********************
> package farmapp.client.weather;
>
> import com.google.gwt.core.client.JavaScriptObject;
> import com.google.gwt.http.client.URL;
> import com.google.gwt.user.client.Window;
> import com.google.gwt.xml.client.Document;
> import com.google.gwt.xml.client.XMLParser;
>
> public class WeatherService {
>
> private int xmlRequestId = 0;
>
> public void getReport(final Integer zipCode, final
> WeatherReportCallback reportCallback){
> String url =
> URL.encode("http://www.google.com/ig/api?weather=";) +
> zipCode.toString() + "&callback=";
> getXml(xmlRequestId++, url, this, reportCallback);
> }
>
> public WeatherReport XmlToReport(String xml){
> WeatherReport result = new WeatherReport();
> Document doc = XMLParser.parse(xml);
> // convert doc to WeatherReport object
> return result;
> }
>
> public void handleXmlResponse(JavaScriptObject xml,
> WeatherReportCallback reportCallback) {
> if (xml == null) {
> Window.alert("Couldn't retrieve XML");
> }
>
> WeatherReport report = XmlToReport(xml.toString());
> reportCallback.onSuccess(report);
> }
>
> private native static void getXml(int requestId, String url,
> WeatherService handler, WeatherReportCallback reportCallback) /*-{
> var callback = "callback" + requestId;
> var script = document.createElement("script");
> script.setAttribute("src", url+callback);
> script.setAttribute("type", "text/javascript");
>
> window[callback] = function(xmlObj) {
> [EMAIL PROTECTED]::handleXmlResponse
> (Lcom/google/gwt/core/client/JavaScriptObject;Lfarmapp/client/weather/
> WeatherReportCallback;)(xmlObj, reportCallback);
> window[callback + "done"] = true;
> }
>
> // set 10-second timeout
> setTimeout(function() {
> if (!window[callback + "done"]) {
> [EMAIL PROTECTED]::handleXmlResponse
> (Lcom/google/gwt/core/client/JavaScriptObject;Lfarmapp/client/weather/
> WeatherReportCallback;)(null, reportCallback);
> }
> // cleanup
> document.body.removeChild(script);
> delete window[callback];
> delete window[callback + "done"];
> }, 10000);
>
> document.body.appendChild(script);
> }-*/;
>
> }
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Google Web Toolkit" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to [EMAIL PROTECTED]
For more options, visit this group at
http://groups.google.com/group/Google-Web-Toolkit?hl=en
-~----------~----~----~----~------~----~------~--~---
