Filters and Interceptors - RESTful Java with JAX-RS 2.0 - page 179

public public void void filter ( ClientRequestContext requestContext ,

ClientResponseContext responseContext )

throws throws IOException ;

}

Let's use these two interfaces to implement a client-side cache. We want this cache to behave
like a browser's cache. This means we want it to honor the Cache-Control semantics dis-
cussed in Chapter 11 . We want cache entries to expire based on the metadata within Cache-
Control response headers. We want to perform conditional GETs if the client is requesting
an expired cache entry. Let's implement our ClientRequestFilter first:

import import javax.ws.rs.client.ClientRequestFilter javax.ws.rs.client.ClientRequestFilter ;

import import javax.ws.rs.client.ClientRequestContext javax.ws.rs.client.ClientRequestContext ;

public public class class ClientCacheRequestFilter ClientCacheRequestFilter implements implements ClientRequestFilter {

private private Cache cache ;

public public ClientCacheRequestFilter ( Cache cache ) {

this this . cache = cache ;

}

public public void throws IOException {

iif (! ctx . getMethod (). equalsIgnoreCase ( "GET" )) return

void filter ( ClientRequestContext ctx ) throws

return ;

CacheEntry entry = cache . getEntry ( request . getUri ());
iif ( entry == null null ) return return ;

iif (! entry . isExpired ()) {
ByteArrayInputStream is = new new ByteArrayInputStream ( entry . getContent ());

Response response = Response . ok ( is )
. type ( entry . getContentType ()). build ();

ctx . abortWith ( response );
return

return ;

}

String etag = entry . getETagHeader ();
String lastModified = entry . getLastModified ();

iif ( etag != null null ) {

ctx . getHeaders . putSingle ( "If-None-Match" , etag );

}

iif ( lastModified != null null ) {

ctx . getHeaders . putSingle ( "If-Modified-Since" , lastModified );

}