How to use CXF, JAX-RS and HTTP Caching

The CXF documentation mentions caching as Advanced HTTP:

CXF JAXRS provides support for a number of advanced HTTP features by handling If-Match, If-Modified-Since and ETags headers. JAXRS Request context object can be used to check the preconditions. Vary, CacheControl, Cookies and Set-Cookies are also supported.

I'm really interested in using (or at least exploring) these features. However, while "provides support" sounds really interes开发者_Go百科ting, it isn't particularly helpful in implementing such features. Any help or pointers on how to use If-Modified-Since, CacheControl or ETags?

Actually, the answer isn't specific to CXF - it's pure JAX-RS:

// IPersonService.java
import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.Request;
import javax.ws.rs.core.Response;

@GET
@Path("/person/{id}")
Response getPerson(@PathParam("id") String id, @Context Request request);


// PersonServiceImpl.java
import javax.ws.rs.core.CacheControl;
import javax.ws.rs.core.EntityTag;
import javax.ws.rs.core.Request;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.Response.ResponseBuilder;

public Response getPerson(String name, Request request) {
  Person person = _dao.getPerson(name);

  if (person == null) {
    return Response.noContent().build();
  }

  EntityTag eTag = new EntityTag(person.getUUID() + "-" + person.getVersion());

  CacheControl cc = new CacheControl();
  cc.setMaxAge(600);

  ResponseBuilder builder = request.evaluatePreconditions(person.getUpdated(), eTag);

  if (builder == null) {
    builder = Response.ok(person);
  }

  return builder.cacheControl(cc).lastModified(person.getUpdated()).build();
}

With the forthcoming JAX-RS 2.0 it will be possible to apply Cache-Control declaratively, as explained in http://jalg.net/2012/09/declarative-cache-control-with-jax-rs-2-0/

You can already test this at least with Jersey. Not sure about CXF and RESTEasy though.

CXF didn't implements dynamic filtering as explained here : http://www.jalg.net/2012/09/declarative-cache-control-with-jax-rs-2-0

And if you use to return directly your own objects and not CXF Response, it's hard to add a cache control header.

I find an elegant way by using a custom annotation and creating a CXF Interceptor that read this annotation and add the header.

So first, create a CacheControl annotation

@Target(ElementType.METHOD )
@Retention(RetentionPolicy.RUNTIME)
public @interface CacheControl {
    String value() default "no-cache";
}

Then, add this annotation to your CXF operation method (interface or implementation it works on both if you use an interface)

@CacheControl("max-age=600")
public Person getPerson(String name) {
    return personService.getPerson(name);
}

Then create a CacheControl interceptor that will handle the annotation and add the header to your response.

public class CacheInterceptor extends AbstractOutDatabindingInterceptor{
    public CacheInterceptor() {
        super(Phase.MARSHAL);
    }

    @Override
    public void handleMessage(Message outMessage) throws Fault {
        //search for a CacheControl annotation on the operation
        OperationResourceInfo resourceInfo = outMessage.getExchange().get(OperationResourceInfo.class);
        CacheControl cacheControl = null;
        for (Annotation annot : resourceInfo.getOutAnnotations()) {
            if(annot instanceof CacheControl) {
                cacheControl = (CacheControl) annot;
                break;
            }
        }

        //fast path for no cache control
        if(cacheControl == null) {
            return;
        }

        //search for existing headers or create new ones
        Map<String, List<String>> headers = (Map<String, List<String>>) outMessage.get(Message.PROTOCOL_HEADERS);
        if (headers == null) {
            headers = new TreeMap<>(String.CASE_INSENSITIVE_ORDER);
            outMessage.put(Message.PROTOCOL_HEADERS, headers);
        }

        //add Cache-Control header
        headers.put("Cache-Control", Collections.singletonList(cacheControl.value()));
    }
}

Finally configure CXF to use your interceptor, you can find all the needed information here : http://cxf.apache.org/docs/interceptors.html

Hope it will help.

Loïc