學習getRequestDispatcher()與sendRedirect()筆記

1、request.getRequestDispatcher().forward(request, response);是請求轉發，前後頁面共享一個request ; 這個是在服務端運行的，對瀏覽器來說是透明的。這種方式跳轉，傳值可以使用三種方法：url中帶parameter，session，request.setAttribute
2、response.sendRedirect()是重新定向，前後頁面不是一個request。而這個是在瀏覽器端運行的。
該方式只適用於無傳值跳轉.
給自己看的並且記錄

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);
    }

    // 根據要修改的id找到所有的屬性
    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);
    }

    // 實現修改的方法
    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));
        // 重定向跳轉
        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()地址欄將改變
2、使用request.getRequestDispatcher().forward(request,response)地址欄中的信息保持不變.
request.setAttribute存的東西
只用通過方法2跳轉 才能在新頁取出來