Filters and Interceptors - RESTful Java with JAX-RS 2.0 - page 188

import import javax.ws.rs.core.CacheControl javax.ws.rs.core.CacheControl ;

@MaxAge
@Provider
public public class class CacheControlFilter CacheControlFilter implements implements ContainerResponseFilter {

@Context ResourceInfo info ;

public public void void filter ( ContainerRequestContext req , ContainerResponseContext res )

throws

throws IOException

{

iif ( req . getMethod (). equals ( "GET" )) {
MaxAge max = info . getMethod (). getAnnotation ( MaxAge . class );
CacheControl cc = new new CacheControl ();

cc . setMaxAge ( max . value ());
req . getHeaders (). add ( "Cache-Control" , cc );

}

}

}

If we bound CacheControlFilter via a name binding, the filter class would have to inject
ResourceInfo , then look up the @MaxAge annotation of the JAX-RS method so it could de-
termine the actual max age value to apply to the Cache-Control header. This is less efficient
at runtime than our DynamicFeature implementation. Sure, in this case the overhead prob-
ably will not be noticeable, but if you have more complex initialization scenarios the over-
head is bound to become a problem.

Exception Processing
So what happens if a filter or interceptor throws an exception? On the server side, the JAX-
RS runtime will process exceptions in the same way as if an exception were thrown in a
JAX-RS method. It will try to find an ExceptionMapper for the exception and then run it. If
an exception is thrown by a ContainerRequestFilter or ReaderInterceptor and mapped
by an ExceptionMapper , then any bound ContainerResponseFilter must be invoked. The
JAX-RS runtime ensures that at most one ExceptionMapper will be invoked in a single re-
quest processing cycle. This avoids infinite loops.

On the client side, if the exception thrown is an instance of WebApplicationException ,
then the runtime will propagate it back to application code. Otherwise, the exception is
wrapped in a javax.ws.rs.client.ProcessingException if it is thrown before the re-
quest goes over the wire. The exception is wrapped in a
javax.ws.rs.client.ResponseProcessingException when processing a response.