Filters and Interceptors - RESTful Java with JAX-RS 2.0 - page 175

Another great use case for request filters is implementing custom authentication protocols.
For example, OAuth 2.0 has a token protocol that is transmitted through the Authorization
HTTP header. Here's what an implementation of that might look like:

import import javax.ws.rs.container.ContainerRequestFilter javax.ws.rs.container.ContainerRequestFilter ;

import import javax.ws.rs.container.ContainerRequestContext javax.ws.rs.container.ContainerRequestContext ;

import import javax.ws.rs.NotAuthorizedException javax.ws.rs.NotAuthorizedException ;

@Provider
@PreMatching
public public class class BearerTokenFilter BearerTokenFilter implements implements ContainerRequestFilter {

public public void throws IOException {

String authHeader = request . getHeaderString ( HttpHeaders . AUTHORIZATION );
iif ( authHeader == null

void filter ( ContainerRequestContext ctx ) throws

new NotAuthorizedException ( "Bearer" );
String token = parseToken ( authHeader );
iif ( verifyToken ( token ) == false

null ) throw throw new

false ) {

throw throw new new NotAuthorizedException ( "Bearer error=\"invalid_token\"" );

}

}

private private String parseToken ( String header ) {...}

private

private boolean boolean verifyToken ( String token ) {...}

}

In this example, if there is no Authorization header or it is invalid, the request is aborted
with a NotAuthorizedException . The client receives a 401 response with a WWW-
Authenticate header set to the value passed into the constructor of NotAuthorizedExcep-
tion . If you want to avoid exception mapping, then you can use the Container-
RequestContext.abortWith() method instead. Generally, however, I prefer to throw ex-
ceptions.

Server Response Filters

Response filters are implementations of the ContainerResponseFilter interface:

package package javax . ws . rs . container ;

public public interface interface ContainerResponseFilter ContainerResponseFilter {

public public void void filter ( ContainerRequestContext requestContext ,

ContainerResponseContext responseContext )

throws throws IOException ;

}