结论

先说结论

request.getRequestDispatcher("/路径").forward(request, response)

1、只能转发到同一个Context下，路径中不用包含ContextPath 2、客户端只发了一次请求 3、浏览器地址栏的URL不会发生变化 4、转发的操作只由服务器完成

重定向

response.sendRedirect("/路径")

1、可以重定向到任意URL,如果重定向到同一个Context下，路径中需要包含ContextPath 2、客户端发了两次请求 3、浏览器地址栏的URL会发生变化 4、重定向的操作由服务器+客户端配合完成

代码举例："/test1"转发到"/test2"再转发到"/test3"

test1:

@WebServlet("/test1")
public class test1 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setAttribute("name", "jack");

        System.out.println("test1Request"+req);

        req.getRequestDispatcher("/test2").forward(req,resp);


    }
}

test2:

@WebServlet("/test2")
public class test2 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("test2Request"+req);

        req.getRequestDispatcher("/test3").forward(req,resp);

    }
}

test3:

@WebServlet("/test3")
public class test3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("test3Request"+req);

    }
}

源码

重定向

resp.sendRedirect("/hello/list");

源码在Response.java的sendRedirect里

设置302状态码和location. `

转发与重定向的区别

结论

转发

重定向