Using WebSockets with EJB 3 - EJB 3 in Action - page 584

Listing 14.14. BulletinService endpoint configuration
In this listing the BulletinService class is annotated with @ServerEndpoint and
will thus be exposed as a WebSocket endpoint . The value parameter specifies the
URI for the server . Assuming the web application is deployed under the chapter 14
context, the full path to the service will be http://<address>:<port>/chapter14/admin/bul-
letin . An encoder is specified for the service that will encode methods being sent using the
BulletinMessadeEncoder . A decoder is also specified that will decode incom-
ing messages . Although multiple encoders and decoders can be specified, only the first
decoder will be used.
@PathParam
The @PathParam annotation serves the same functional purpose as the javax.ws.rs
.PathParam annotation you saw earlier when we covered RESTful web services in
chapter 8 . With it, you can map variables in the URI to parameters on methods annotated
with @OnMessage , @OnError , @OnOpen , and @OnClose. This enables parameters to
be passed in using the URL and can help to reduce the complexity of application messages
exchanged via WebSockets. The annotation is defined as follows:
@Target(value = {ElementType.PARAMETER,
ElementType.METHOD, ElementType.FIELD})
@Retention(value = RetentionPolicy.RUNTIME)
@Documented
public @interface PathParam {
public String value();
}
As you can see from this definition, there's only one parameter to the @PathParam an-
notation and that's the variable, which should also appear in the URI specified by the
@ServerEndpoint annotation. The WebSocket implementation will attempt to convert