Question

I am developing REST web services using Jersey and I need to call a servlet from web service methods to authenticate the user. I get exceptions when running the below code:

@Path("/server")
public class WebServer {
    @Resource
    private WebServiceContext context;  

    @POST
    @Path("/post")
    @Consumes(MediaType.APPLICATION_JSON)
    public Response createTrackInJSON(Track track) throws IOException, ServletException { 
        ServletContext servletContext = (ServletContext) context.getMessageContext()
            .get(MessageContext.SERVLET_CONTEXT); // Here I am getting NPE

        HttpServletRequest request = (HttpServletRequest) context.getMessageContext()
            .get(MessageContext.SERVLET_REQUEST);

        HttpServletResponse response = (HttpServletResponse) context.getMessageContext()
            .get(MessageContext.SERVLET_RESPONSE);

        request.setAttribute("username", track.getUsername());
        request.setAttribute("password", track.getPassword());
        servletContext.getRequestDispatcher("/LoginAction").include(request, response);

        String loginStatus = request.getParameter("loginStatus");
        String Token = request.getParameter("Token");
        String result = ""+track;
        return Response.status(200).entity(result).build();
    }
}

The exception is:

java.lang.NullPointerException at
com.webservices.server.WebServer.createTrackInJSON(WebServer.java:36)
…servletContext is null

Please help me determine how to get the servlet context in a web service.

Answer 1

Use the @Context annotation, and inject the correct class. You can also directly inject the servlet request and response objects.

import jax.ws.rs.core.Context;

@Path("/server")
public class WebServer {
    @Context 
    private ServletContext context; 

    @Context
    private HttpServletRequest request;

    @Context
    private HttpServletResponse response;

    // ...
}