学习getRequestDispatcher()与sendRedirect()笔记

拼搏现实的明天。 2022-06-02 01:14 163阅读 0赞

1、request.getRequestDispatcher().forward(request, response);是请求转发，前后页面共享一个request ; 这个是在服务端运行的，对浏览器来说是透明的。**这种方式跳转，传值可以使用三种方法：url中带parameter，session，request.setAttribute**  
2、response.sendRedirect()是重新定向，前后页面不是一个request。而这个是在浏览器端运行的。  
**该方式只适用于无传值跳转.**  
**给自己看的并且记录**

StudentServiceImple ssi = new StudentServiceImple();
        List<Student> list;
        Scanner input = new Scanner(System.in);
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            String op = request.getParameter("op");
            System.out.println(op);
            if ("update1".equals(op)) {
                update1Student(request, response);
            } else if ("update2".equals(op)) {
                update2Student(request, response);
            }  else if ("add".equals(op)) {
                addStudent(request, response);
            } else if ("add2".equals(op)) {
                addStudent2(request, response);
            } else {
                list = ssi.queryAll();
                request.setAttribute("students", list);
                getServletContext().getRequestDispatcher("/studentServlet.jsp").forward(request, response);
            }
    
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            doGet(request, response);
        }
    
        // 根据要修改的id找到所有的属性
        public void update1Student(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            for (Student s : list) {
                int id = Integer.valueOf(request.getParameter("id"));
                if (id == s.getId()) {
                    request.setAttribute("student", s);
                    break;
                }
            }
            getServletContext().getRequestDispatcher("/update.jsp").forward(request, response);
        }
    
        // 实现修改的方法
        public void update2Student(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            int id = Integer.valueOf(request.getParameter("id"));
            String sname = request.getParameter("name");
            String ssex = request.getParameter("sex");
            ssi.updateStudent(new Student(id, sname, ssex, 0));
            // 重定向跳转
            System.out.println("==================================");
            response.sendRedirect("StudentServlet");
        }
    
        public void addStudent(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            response.sendRedirect("addStudent.jsp");
    
        }
    
        public void addStudent2(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
    
            int id = Integer.valueOf(request.getParameter("id"));
            String sname = request.getParameter("sname");
            String ssex = request.getParameter("ssex");
            int tid = Integer.valueOf(request.getParameter("stid"));
            System.out.println(id + sname + ssex+tid);
            ssi.addStudent(new Student(id, sname, ssex, tid));
            response.sendRedirect("StudentServlet");
        }

1、使用response.sendRedirect()地址栏将改变  
2、使用request.getRequestDispatcher().forward(request,response)地址栏中的信息保持不变.  
request.setAttribute存的东西  
只用通过方法2跳转 才能在新页取出来