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Understanding AtmosphereInterceptor
jfarcand edited this page Jun 8, 2012
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The Framework ships with several implementation of AtmosphereInterceptor. Interceptor are called before and after AtmosphereHandler. You can define AtmosphereInterceptor that apply to all AtmosphereHandler by annotating them using:
@AtmosphereInterceptorService
or per Meteor or AtmosphereHandler using
@MeteorService(interceptors={...}) @AtmosphereHandlerService(interceptors={...})
You can also define them in web/atmosphere.xml
// application.xml <applicationConfig> <param-name>org.atmosphere.cpr.AtmosphereInterceptor</param-name> <param-value>list of classes</param-value> </applicationConfig> // web.xml <init-param> <param-name>org.atmosphere.cpr.AtmosphereInterceptor</param-name> <param-value>list of classes</param-value> </init-param>
or per AtmosphereHandler in atmosphere.xml
<atmosphere-handler support-session="true" context-root="/*" class-name="..." broadcaster="..." broadcasterCache="" broadcastFilterClasses="" interceptorClasses="" comet-support="" >
AtmosphereInterceptor allows an application to customize the request/response before they get delivered to the AtmosphereHandler. Atmosphere ships with several implementation:
- SSEAtmosphereInterceptor: Add supports for HTML5 Server Side Events. Installed by default.
- CometdAtmosphereInterceptor: The support for the Cometd framework.
- JSONPAtmosphereInterceptor: Add supports for JSONP/Callback transport. Installed by default.
- AtmosphereResourceLifecycleInterceptor: Manage the life cycle of an AtmosphereResource. By default, the interceptor always suspend GET requests, and automatically resume/flush/handle the Response's state.
- MessageLengthInterceptor: An interceptor that add a special String "|" at the end of a broadcasted message, allowing the atmosphere.js javascript client to detect if one or several messages where aggregated in one write operations and delivered as a single message.
- BroadcastOnPostAtmosphereInterceptor : An interceptor that broadcast the request's body after it has been delivered to an AtmosphereHandler.
Without interceptor, an AtmosphereHandler would looks like
@AtmosphereHandlerService(path="/chat") public class ChatAtmosphereHandler implements AtmosphereHandler { @Override public void onRequest(AtmosphereResource r) throws IOException { AtmosphereRequest req = r.getRequest(); // First, tell Atmosphere // to allow bi-directional communication by suspending. if (req.getMethod().equalsIgnoreCase("GET")) { r.suspend(); // Second, broadcast message to all connected users. } else if (req.getMethod().equalsIgnoreCase("POST")) { r.getBroadcaster().broadcast(req.getReader().readLine().trim()); } } @Override public void onStateChange(AtmosphereResourceEvent event) throws IOException { AtmosphereResource r = event.getResource(); AtmosphereResponse res = r.getResponse(); if (event.isSuspended()) { ... switch (r.transport()) { case JSONP: case AJAX: case LONG_POLLING: event.getResource().resume(); break; default: res.getWriter().flush(); break; } } }
Now let the framework manage the Atmosphereresource dore :
@AtmosphereHandlerService(path = "/chat", interceptors= {AtmosphereResourceLifecycleInterceptor.class}) public class SocketIOChatAtmosphereHandler implements AtmosphereHandler { @Override public void onRequest(AtmosphereResource r) throws IOException { r.getBroadcaster().broadcast(r.getRequest().getReader().readLine()); } @Override public void onStateChange(AtmosphereResourceEvent event) throws IOException { AtmosphereResource r = event.getResource(); AtmosphereResponse res = r.getResponse(); if (event.isSuspended()) { ..... } }
Better, if you don't want to handle the broadcast operation as well, just do:
@AtmosphereHandlerService(path = "/chat", interceptors= {AtmosphereResourceLifecycleInterceptor.class, BroadcastOnPostAtmosphereInterceptor.class}) public class SocketIOChatAtmosphereHandler implements AtmosphereHandler { @Override public void onRequest(AtmosphereResource r) throws IOException { } @Override public void onStateChange(AtmosphereResourceEvent event) throws IOException { AtmosphereResource r = event.getResource(); AtmosphereResponse res = r.getResponse(); if (event.isSuspended()) { ..... } }