Salut,
I've just wrote a demo hacking the code described in that blog (I'm far
from a GWT expert):
*
http://is.gd/2Kk7wIt pretty old code but it was quite simple for me to change the demo and
make it works on top of Atmosphere. The code is a little bit hacked I
admit but it is pretty simple to understand. The sample (an Auction
Demo) defines two Servlet, one for suspending connection:
*
http://is.gd/2Klxoand one for broadcasting bids, invoked by GWT when events happens on the
screen:
*
http://is.gd/2Kls2First, you need to do is to defines them inside your atmosphere.xml:
> <atmosphere-handlers>
> <atmosphere-handler context-root="/streamingService"
> class-name="org.atmosphere.handler.ReflectorServletProcessor">
> <property name="servletClass" value="org.gwtcomet.server.StreamingServiceImpl"/>
> </atmosphere-handler>
> <atmosphere-handler context-root="/streamingServlet"
> class-name="org.atmosphere.handler.ReflectorServletProcessor">
> <property name="servletClass" value="org.gwtcomet.server.StreamingServlet"/>
> </atmosphere-handler>
> </atmosphere-handlers>
using the ReflectorServletProcessor (which will run those Servlets). The
web.xml looks like:
> <description>Atmosphere GWT Auction</description>
> <display-name>Atmosphere Auction</display-name>
> <servlet>
> <description>AtmosphereServlet</description>
> <servlet-name>AtmosphereServlet</servlet-name>
> <servlet-class>org.atmosphere.cpr.AtmosphereServlet</servlet-class>
> <!-- Uncomment if you want to use Servlet 3.0 Async Support
> <async-supported>true</async-supported>
> -->
> <load-on-startup>0</load-on-startup>
> </servlet>
> <servlet-mapping>
> <servlet-name>AtmosphereServlet</servlet-name>
> <url-pattern>/streamingServlet</url-pattern>
> </servlet-mapping>
> <servlet-mapping>
> <servlet-name>AtmosphereServlet</servlet-name>
> <url-pattern>/streamingService</url-pattern>
> </servlet-mapping>
Mainly, we are mapping the AtmosphereServlet in order to let it dispatch
later to it's AtmosphereHandler (the Servlets)
In the Servlet that does the suspend, we just need to do:
> 95 AtmosphereEvent e =
> 96 (AtmosphereEvent) request.getAttribute("org.atmosphere.cpr.AtmosphereEvent");
> 97
> 98 if (!e.getBroadcaster().getName().equals("GWT")){
> 99 synchronized(e.getBroadcaster()){
> 100 e.getBroadcaster().setName("GWT");
> 101 e.getBroadcaster().getBroadcasterConfig().addFilter(new GWTBroadcasterFilter());
> 102 }
> 103 }
> 104
> 105 e.suspend();
Just getting the AtmosphereEvent, name our Broadcaster 'GWT' and suspend
the connection. I've defined a BroascastFilter that does:
> 119 private final class GWTBroadcasterFilter implements BroadcastFilter {
> 120
> 121 public Object filter(Object message) {
> 122 try {
> 123 StreamingServiceBusiness.Event event = (StreamingServiceBusiness.Event) message;
> 124 StringBuffer stream = new StringBuffer();
> 125 stream.append("<script type='text/javascript'>\n");
> 126 stream.append("\twindow.parent.callback('" + event.queueName +
> 127 "',unescape('" + URLEncoder.encode(event.message, "iso-8859-1")
> 128 .replaceAll("\\x2B", "%20") + "'));\n");
> 129 stream.append("</script>\n");
> 130 return stream;
> 131 } catch (UnsupportedEncodingException ex) {
> 132 Logger.getLogger(StreamingServlet.class.getName()).log(Level.SEVERE, null, ex);
> 133 }
> 134 return message;
Transform an Object into a StringBuffer (that was the original code). In
the second Servlet (the one that will be invoked by GWT), I just
retrieve the Broadcaster and do:
>
> public void sendMessage(String queueName, String message) {
> try {
> bl.lookup("GWT").broadcast(new StreamingServiceBusiness.Event(queueName, message));
> } catch (OutOfScopeException ex) {
> Logger.getLogger(StreamingServiceImpl.class.getName()).log(Level.SEVERE, null, ex);
> }
> }
That's all :-) You can download the complete sample & code from here
(once uploaded under gwt-auction)
*
http://is.gd/2KlMqor checkout the workspace.
Let me know how it goes.
-- Jeanfrancois
Jeanfrancois Arcand wrote:
> Saltu,
>
> asianCoolz wrote:
>> anyone already tried integrate with gwt ? can share your experiences and
>> maybe guides/tutorials?
>
> It should be simple to run on top of GWT. I haven't try but let me share
> how this can be achieved (I will try to write a sample next week).
> Mainly, you will first need to define your web.xml like:
>
>> <description>Atmosphere GWT</description>
>> <display-name>Atmosphere GWT</display-name>
>> <servlet>
>> <description>AtmosphereServlet</description>
>> <servlet-name>AtmosphereServlet</servlet-name>
>>
>> <servlet-class>org.atmosphere.cpr.AtmosphereServlet</servlet-class>
>> <load-on-startup>0</load-on-startup>
>> </servlet>
>> <servlet-mapping>
>> <servlet-name>AtmosphereServlet</servlet-name>
>> <url-pattern>/*</url-pattern>
>> </servlet-mapping>
>
> Next, you will add define your GWT Servlet inside your atmosphere.xml:
>
>> <atmosphere-handlers>
>> <atmosphere-handler context-root="/resources"
>> class-name="org.atmosphere.handler.ReflectorServletProcessor"
>> broadcaster="org.atmosphere.cpr.DefaultBroadcaster">
>> <property name="servletClass" value="foo.bar.yourGWTServlet"/>
>> </atmosphere-handler>
>> </atmosphere-handlers>
>
> Inside your GWT Servlet (which extends
> com.google.gwt.user.server.rpc.RemoteServiceServlet)
>
> You will get the AtmosphereEvent:
>
> *
http://is.gd/2E6kp>
> By doing:
>
> AtmosphereEvent e =
> HttpServletRequest.getAttribute("org.atmosphere.cpr.AtmosphereEvent");
>
> Then you can invoke e.suspend(), e.resume() or
> e.getBroadcaster().broadcast(...) as needed.
>
> Hope that help.
>
> -- Jeanfrancois
>
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