Filter and interceptors

JAX-RS 2.0 added ContainerRequestFilter and ContainerResponseFilter to modify the request context. It is executed around the method invocation but has already passed the method resolution. On a high level, it can be seen as a CDI interceptor but only at the HTTP layer. These filters do not impact significantly the performance until they do a lot of logic, and there are a few cases where it is a good place to put some logic. One very common example is to validate a security token or log in a user based on the HTTP headers. Don't be surprised to see this kind of component while investigating what your application is doing.

In the same spirit, ReaderInterceptor and WriterInterceptor intercept MessageBodyReader or MessageBodyWriter. They are intended to wrap the input/output streams to add some support such as GZIP compression. However, since we are close to the current I/O, we need to take care to not add too much logic here if the payloads are huge or if the algorithm is complex. In fact, since the stream operations are called very often, a badly implemented wrapper can affect the performance.