Dropwizard Add Response Filter for All Resources

Question

How can I add a filter to my Dropwizard application that will validate the response that every resource is returning?

Should I use javax.servlet.Filter or javax.ws.rs.container.ContainerResponseFilter

Any examples pertaining to its uses would be appreciated.

Answer 1

To add a response filter for all the resources using dropwizard you can do the following :

1. Create a CustomFilter that extends javax.servlet.Filter -

   public class CustomFilter implements Filter {
   
       public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
           // your filtering task
           chain.doFilter(req, res);
       }
   
       public void init(FilterConfig filterConfig) {
       }
   
       public void destroy() {
       }
   }
   

2. Then register the same to your Service that extends Application -

   public class CustomService extends Application<CustomConfig> { //CustomConfig extend 'io.dropwizard.Configuration'
   
     public static void main(String[] args) throws Exception {
       new CustomService().run(args);
     }
   
     @Override
     public void initialize(Bootstrap<CustomConfig> someConfigBootstrap) {
       // do some initialization
     }
   
     @Override
     public void run(CustomConfig config, io.dropwizard.setup.Environment environment) throws Exception {
       ... // resource registration
       environment.servlets().addFilter("Custom-Filter", CustomFilter.class)
           .addMappingForUrlPatterns(java.util.EnumSet.allOf(javax.servlet.DispatcherType.class), true, "/*");
     }
   }
   

3. You should now be good to be filtering all the resources using the CustomFilter defined above.

Answer 2

I think what you want to use is javax.servlet.Filter.

A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.

More info here.