学习getRequestDispatcher()与sendRedirect()笔记_getrequestdispatcher 参数传递

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");
    }
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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