Question

We have built some REST (jax-rs) web services using Apache CXF. They return a JSON response.

I now need to modify some of the request parameters, and response content. (Basically we need to encode/encrypt some of the data that is returned by the service; and decode/decrypt the same data when it is used as a parameter in a subsequent service call.)

It seems I have at least 4 options here:

1. Use a Servlet filter
2. Use a CXF Interceptor
3. Use a JAX-RS Filter
4. Don’t use any particular pattern, and perform the encode/decode within the actual service logic.

I’ve used Servlet Filters before, and understand exactly how to modify request params and response body, so I’m leaning toward that. However, I’m open to using a CXF Interceptor or JAX-RS filter if that is the more ‘correct’ way to solve this when using CXF. But based on the documentation, I don’t really understand how to do this. For example, do I use the setContent method of the Message object to change the JSON response? What is the format parameter in that case, just String.class?

Answer 1

Answering my own question here … I ended up using a JAX-RS filter, and it worked well, once I got past the lack of documentation. I used the (rather sparse) documentation from http://cxf.apache.org/docs/jax-rs-filters.html . Note despite it’s name, a JAX-RS filter is a CXF-specific beast, not part of the JAX-RS standard (as far as I can tell).

Here is some example code:

@Context
private HttpServletRequest httpRequest;
@Context
private UriInfo uriInfo;

/**
 * @see org.apache.cxf.jaxrs.ext.ResponseHandler#handleResponse(org.apache.cxf.message.Message, org.apache.cxf.jaxrs.model.OperationResourceInfo, javax.ws.rs.core.Response)
 */
public Response handleResponse(Message message, OperationResourceInfo opResourceInfo, Response response) {
    try {

        // log the injected context data; useful for debugging CXF problems
        logContextData(httpRequest, uriInfo);

        OutputStream os = message.getContent(OutputStream.class);
        String relevantData = getDataFromRequest(httpRequest);
        message.setContent(OutputStream.class, new MyOutputStreamWrapper(os, relevantData));

    } catch (CustomException e) {
            // return some status that is related to CustomException
        return Response.status(Status.UNAUTHORIZED).build();
    } catch (Exception e) {
        return Response.status(Status.INTERNAL_SERVER_ERROR).build();
    }

    return response;
}

/**
 * @see org.apache.cxf.jaxrs.ext.RequestHandler#handleRequest(org.apache.cxf.message.Message, org.apache.cxf.jaxrs.model.ClassResourceInfo)
 */
public Response handleRequest(Message message, ClassResourceInfo classResourceInfo) {
    try {

        // log the injected context data; useful for debugging CXF problems
        logContextData();

        String updatedQueryString = buildNewQueryString(this.uriInfo, httpRequest);

        message.put(Message.QUERY_STRING, updatedQueryString);


        // returning null tells CXF to continue the request (i.e. a non-null value would halt the request)
        return null;

    } catch (CustomException e) {
        // return some status that is related to CustomException
        return Response.status(Status.UNAUTHORIZED).build();
    } catch (Exception e) {
        return Response.status(Status.INTERNAL_SERVER_ERROR).build();
    }
}

I should note that the implementation of MyOutputStreamWrapper is the important part in modifying the response content. I couldn’t include that source here (in fact my implementation has a different name) due to security considerations.