How to decorate the json response with Resteasy

Question

I am implementing a restfull service with Resteasy that will be consumed by a Extjs client, and i want to decorate the json object retrieved in the http response with some more attributes without using a wrapper class with additional attributes in the service method or overriding JacksonJsonProvider
Example:

raw object:

{
   "id":"1",
   "name":"Diego"
}

decorated object:

{
   "success":"true",
   "root":{
             "id":"1",
             "name":"Diego"
          }
}

I found JAXB Decorators but i could not implement a decorator for json type.

I tried to replace the entity that will be serialized with a wrapper using Interceptors but it doesn't work if a replace the entity which is a Collection.

Any suggestions?

score 1 · Accepted Answer · edited May 26 '16 at 14:37

You could write an Interceptor that wraps your JSON response before it is passed to the client. Here is an example code:

Define custom HTTPServletResponseWrapper

public class MyResponseWrapper extends HttpServletResponseWrapper {
    private ByteArrayOutputStream byteStream;

    public MyResponseWrapper(HttpServletResponse response, ByteArrayOutputStream byteStream) {
        super(response);
        this.byteStream = byteStream;
    }

    @Override
    public ServletOutputStream getOutputStream() throws IOException {
        return new ServletOutputStream() {
            @Override
            public void write(int b) throws IOException {
                byteStream.write(b);
            }
        };
    }
    @Override
    public PrintWriter getWriter() throws IOException {
        return new PrintWriter(byteStream);
    }
}

Define filter class:

@WebFilter("/rest/*")
public class JSONResponseFilter implements Filter {

    private final String JSON_RESPONSE = " { \"success\":\"true\", \"root\": ";
    private final String JSON_RESPONSE_CLOSE = "}";

    /* .. */

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {

        // capture result in byteStream by using custom responseWrapper
        final HttpServletResponse httpResponse = (HttpServletResponse) response;
        final ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        HttpServletResponseWrapper responseWrapper = new MyResponseWrapper(httpResponse, byteStream);

        // do normal processing but capture results in "byteStream"
        chain.doFilter(request, responseWrapper);

        // finally, wrap response with custom JSON
      // you can do fancier stuff here, but you get the idea
        out.write(JSON_RESPONSE.getBytes());
        out.write(byteStream.toByteArray());
        out.write(JSON_RESPONSE_CLOSE.getBytes());
    }
}

How to decorate the json response with Resteasy

1 Answers1