JAX-RS - Filters

JAX-RS filters can be used to modify request or response parameters like headers. It can also be used for things like authentication, logging, auditing, data conversion/transformation/compression, localization targeting etc.

To add filters, we need to implement ContainerRequestFilter and/or ContainerResponseFilter, they are individually used for request and response respectively.

For automatic discovery, we should use @Provider annotation on the filters.

By default, request filters are invoked at the point when a resource method has been selected already but has not been called yet. We can change this behavior by using @PreMatching so that a filter will be called before resource matching (next tutorial).

By default, just like all the other providers, a single instance of each Filter is instantiated for each JAX-RS application.

Let's see a quick example how to use filters in JAX-RS

Example

Implementing Filter

@Provider
public class LogFilter implements ContainerRequestFilter, ContainerResponseFilter {

  @Override
  public void filter(ContainerRequestContext reqContext) throws IOException {
      System.out.println("-- req info --");
      log(reqContext.getUriInfo(), reqContext.getHeaders());

  }

  @Override
  public void filter(ContainerRequestContext reqContext,
                     ContainerResponseContext resContext) throws IOException {
      System.out.println("-- res info --");
      log(reqContext.getUriInfo(), resContext.getHeaders());


  }

  private void log(UriInfo uriInfo, MultivaluedMap<String, ?> headers) {
      System.out.println("Path: " + uriInfo.getPath());
      headers.entrySet().forEach(h -> System.out.println(h.getKey() + ": " + h.getValue()));
  }
}

A JAX-RS resource

@Path("/")
public class MyResource {

  @GET
  @Path("{path:.*}")
  public String getResponse(@PathParam("path") String path) {
      return "dummy-response for " + path;
  }
}

mvn tomcat7:run-war

Output

Using HTTPie to access the resource:

On Server console:

-- req info --
Path: app
host: [localhost:8080]
connection: [keep-alive]
accept-encoding: [gzip, deflate]
accept: [*/*]
user-agent: [HTTPie/0.9.9]
-- res info --
Path: app
Content-Type: [text/plain]

Example Project

Dependencies and Technologies Used:

• jersey-server 2.25.1: Jersey core server implementation.
• jersey-container-servlet 2.25.1: Jersey core Servlet 3.x implementation.
• JDK 1.8
• Maven 3.3.9