java - JSP - 如何首先转发到 View ，然后在后台继续处理方法？

Question

我想先转发到 View “/WEB-INF/views/searchResult.jsp”，然后在后台处理Calculator.lookUp(Type, Place)。

当前首先处理Calculator.lookUp(Type, Place)，只有当该方法完成后，用户才会转发到“/WEB-INF/views/searchResult.jsp”。感谢您的帮助!

@WebServlet(urlPatterns="/search.do")
public class SrchServlet extends HttpServlet{

      protected void doPost(HttpServletRequest request, 
                HttpServletResponse response) 
          throws ServletException, IOException {

          String Type = request.getParameter("Type");
          String Place = request.getParameter("Place");


          request.setAttribute("Type", Type);
          request.setAttribute("Place", Place);

          //I want the forward to searchResult.jsp to occur
          request.getRequestDispatcher("/WEB-INF/views/searchResult.jsp").forward(
                  request, response);

          //and then in backend for the below method to run
          Calculator.lookUp(Type, Place);

          }   
}

Answer 1

如果您不喜欢异步请求，请备注一些。首先，转发是确定的:您将手交给另一个 servlet，并且下一条指令(如果有)将永远不会被执行。如果您想按顺序继续，则需要包含 JSP。并且有一个技巧可以使响应立即发送到客户端，同时允许在 servlet 中进行处理:只需关闭响应输出写入器或流。

您的代码可以简单地变成:

      //I want the include searchResult.jsp
      request.getRequestDispatcher("/WEB-INF/views/searchResult.jsp").include(
              request, response);

      // cause the response to be sent to the client
      try {
          response.getOutputStream().close(); // if the OutputStream was used
      }
      catch(IllegalStateException e) {
          response.getWriter().close();       // if the Writer was used
      }

      //and then in backend for the below method to run
      Calculator.lookUp(Type, Place);

      }   

我无法确定每个 servlet 规范是否明确允许这样做，但我可以确认 Tomcat 支持它。

不需要任何@Asinc...