How to cache response with Jersey?

Question

I am trying to develop restful API using Jersey.I have GET API's for a particular get operation my GET is taking same time from the same client. Is it possible to cache response? Any pointers is appreciated.

Thanks

Answer 1

Summary of solutions:

1. Request as method parameter

   Interface:

    @Path("myentity")
    public interface MyEntityResource
   
        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public Response getMyEntity(@Context final Request request);
    }
   

   Implementation:

    public class MyEntityResourceImpl implements MyEntityResource
   
        @Override
        public Response getMyEntity(final Request request) {
   
            final MyEntity myEntity = ... // load entity
            final String eTagValue = ... // calclutate value of ETag
   
            final EntityTag eTag = new EntityTag(eTagValue);
   
            ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
            if (responseBuilder == null) {
                return Response.ok(user).tag(eTag).build();
            }
   
            return responseBuilder.build();
        }
    }
   

   Disadvantages:

   • implementation detail Requestis exposed

   • return type Reponse is generic

   • missing grammar of return type in WADL

   • client proxy with unnecessary parameter Request

2. Request as instance variable

   Interface:

    @Path("myentity")
    public interface MyEntityResource
   
        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public Response getMyEntity();
    }
   

   Implementation:

    public class MyEntityResourceImpl implements MyEntityResource
   
        @Context
        private Request request
   
        @Override
        public Response getMyEntity() {
   
            final MyEntity myEntity = ... // load entity
            final String eTagValue = ... // calclutate value of ETag
   
            final EntityTag eTag = new EntityTag(eTagValue);
   
            ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
            if (responseBuilder == null) {
                return Response.ok(user).tag(eTag).build();
            }
   
            return responseBuilder.build();
        }
    }
   

   Disadvantages:

   • return type Reponse is generic

   • missing grammar of return type in WADL

   • dependency injection with @Context is complicated, see https://stackoverflow.com/questions/33240443

3. ShallowEtagHeaderFilter as web filter

   web.xml:

    <filter>
        <filter-name>etagFilter</filter-name>
        <filter-class>org.springframework.web.filter.ShallowEtagHeaderFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>etagFilter</filter-name>
        <url-pattern>/api/*</url-pattern>
    </filter-mapping>
   

   Interface:

    @Path("myentity")
    public interface MyEntityResource
   
        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public MyEntity getMyEntity();
    }
   

   Implementation:

    public class MyEntityResourceImpl implements MyEntityResource
   
        @Override
        public MyEntity getMyEntity() {
   
            final MyEntity myEntity = ... // load entity
            return myEntity;
        }
    }
   

   Disadvantages:

   • bad server performance, see JavaDoc

   • works only on uncommitted response

   • no support of weak ETag

4. Custom WriterInterceptor as JAX-RS Interceptor

   Interceptor:

    public class CustomInterceptor implements WriterInterceptor {
   
        @Context
        private Request request;
   
        @Override
        public void aroundWriteTo(WriterInterceptorContext context) throws IOException, WebApplicationException {
   
            OutputStream old = context.getOutputStream();
   
            ByteArrayOutputStream buffer = new ByteArrayOutputStream();
   
            try {
   
                context.setOutputStream(buffer);
                context.proceed();
   
                byte[] entity = buffer.toByteArray();
   
                String etag = ... // calclutate value of ETag
                context.getHeaders().putSingle(HttpHeaders.ETAG, etag);
   
                ResponseBuilder responseBuilder = request.evaluatePreconditions(eTag);
   
                if (responseBuilder == null) {
                     throw new WebApplicationException(responseBuilder.status(Response.Status.NOT_MODIFIED).header(HttpHeaders.ETAG, etag).build());
                }
   
                old.write(entity);
   
            } finally {
                context.setOutputStream(old);
            }
        }
    }
   

   See also: ServerCacheInterceptor (Resteasy)

   Interface:

    @Path("myentity")
    public interface MyEntityResource
   
        @GET
        @Produces(MediaType.APPLICATION_JSON)
        public MyEntity getMyEntity();
    }
   

   Implementation:

    public class MyEntityResourceImpl implements MyEntityResource
   
        @Override
        public MyEntity getMyEntity() {
   
            final MyEntity myEntity = ... // load entity
            return myEntity;
        }
    }
   

   Disadvantages:

   • no predefined interceptor for Jersey available

   • bad server performance

   • no support of weak ETag

   • ugly workaround with WebApplicationException

Answer 2

Recently I've been solving a similar (if not the same) problem. As a side result of it the following library emerged: https://github.com/AndreyLebedenko/dropwizard-caching-filter

The way it can be used is like below:

@GET
@Produces(MediaType.APPLICATION_JSON)
@Path("/cached")
@ResponseCachedByFilter(10000)
public Object getCached() {
    return dao.get();
} 

Hope it helps.