Viewable in JAX-RS

Question

in our previous project we have used Viewable (at that time we had Jersey as an implementation of JAX-RS). Now we want to run it in WebSphere 8.5. It is a JEE6 server and Viewable is not supported by default of JAX-RS. As implementation of JAX-RS Apache Wink is used there.

What is the best way for answers as HTML with internal objects? We want to use a rendering engine.

Thanx, Robert

Answer 1

If you need to display simple jsp page you can just inject request and do the normal forward like this:

@Path("/service")
public class RestService {

    @Context
    HttpServletRequest request;
    @Context
    HttpServletResponse response;


    @GET
    @Path("/getPage")
    public void getPage() {
        try {
            request.getRequestDispatcher("/mypage.jsp").forward(request, response);
        } catch (ServletException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
} 

Answer 2

Write your own Viewable, then write a MessageBodyWriter<Viewable> which knows how to render it using your rendering engine.

For example, i wrote this:

public record Viewable(String templateName, Map<String, Object> parameters) {}

And then this (irrelevant details of templating omitted):

@Provider
@Produces(MediaType.TEXT_HTML)
public class ViewableMessageBodyWriter implements MessageBodyWriter<Viewable> {

    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type.equals(Viewable.class) && mediaType.equals(MediaType.TEXT_HTML_TYPE);
    }

    @Override
    public void writeTo(Viewable viewable, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType, MultivaluedMap<String, Object> headers, OutputStream body) throws IOException, WebApplicationException {
        String templateFileName = viewable.templateName() + ".html";
        Map<String, Object> parameters = viewable.parameters();
        try (Writer out = new OutputStreamWriter(body)) {
            // load the template file, run the templating engine, and write the result to the output writer
        }
    }

}

That worked fine under Helidon MP 4.0.5.