java HttpServlet必须响应请求吗？

Question

我有几个servlet在服务器端做一些事情。在一些情况下，我只是对一些不必要的数据进行编码并将其发回，这似乎毫无意义。你必须回应吗？当你说return时会发生什么？我以前做过这件事，似乎没有什么问题，但我对servlet相对来说是新手。简单地返回到我头上有什么后果吗？当你回来的时候会发生什么

if(request.getParameter("name").equals("saveusedcards")) {
        String sessId = request.getSession().getId();
        //encode request with confirmation that cards were successfully updated
        if(usersUpdatedCards.get(sessId).isEmpty()){
            //no cards were seen

        }
        boolean success = DataDAO.updateCards(usersUpdatedCards.get(sessId));

        if(success){
            System.out.println("Data base update successfull!");
            String responseMessage = new Gson().toJson("card successfully udpated");
            response.setContentType("application/json");
            response.setCharacterEncoding("UTF-8");
            System.out.println("updated cards response message: "+responseMessage);
            response.getWriter().write(responseMessage);
            return;
        } else {
            System.out.println("Data base update failed...");
            String responseMessage = new Gson().toJson("card was not successfully updated");
            response.setContentType("application/json");
            response.setCharacterEncoding("UTF-8");
            System.out.println("updated cards response message: "+responseMessage);
            response.getWriter().write(responseMessage);
            return;
        }
    } 

Answer 1

servlet必须为客户机生成HTTP响应，但是在响应体中不返回任何内容是完全可以接受的。在执行此操作时，servlet应该通过发送204（无内容）的响应代码向客户机说明这一点。参考：https://httpstatuses.com/204

下面是一个如何从doGet方法设置响应代码的示例。您可以通过doPost或service方法执行同样的操作

@Override
public void doGet(HttpServletRequest request, HttpServletResponse response)
               throws IOException, ServletException {

    // Do whatever work you need to do here...

    res.setStatus(HttpServletResponse. SC_NO_CONTENT);  // This returns a 204
}