Building RESTful Web Services - Introducing Java EE 7 - page 123

@Provider
class AlertFilter implements ContainerRequestFilter,
ContainerResponseFilter {

@Override
public void filter(ContainerRequestContext requestContext)
throws IOException {
alert(requestContext);
}

@Override
public void filter(ContainerRequestContext crc, ContainerResponseContext crc1) throws
IOException {
alert(crc);
}

public void alert(ContainerRequestContext context) {
try(InputStream in = context.getEntityStream();) {
if (in != null) {
InputStreamReader inreader = new InputStreamReader(in);
BufferedReader reader = new BufferedReader(inreader);
String text = "";

while ((text = reader.readLine()) != null) {
System.out.println(text);

}

}
} catch (IOException ex) {
// Error handling
}
}
}

■ Both filter methods in the implementation are required because each accepts different parameters,
and implementing the ContainerRequestFilter and ContainerResponseFilter require it.

Note

Note that the AlertFilter class is decorated with the @Provider annotation. That is because all filters and
interceptors are provider classes and must be annotated as such. The filter must implement ContainerRequestFilter
and ContainerResponseFilter since it is a server-side filter implementation. These two classes provide information
regarding the filter, such as URIs, headers, and so on.
Filters are grouped into chains, and each of the extension points contains their own filter chain. The filters in
the chain are executed in order of precedence via priority. To learn more about setting the priority, please refer to the
“Filter and Interceptor Priorities” section. If a request filter needs to be executed upon receiving a request but before
a resource is matched, then the @PreMatching annotation can be placed on that filter.