请求转发

html（action对应Servlet的映射地址）
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<center>
    <form action="/hello" method="post">
         user<input type="text" name="user"><br>
        password<input type="password" name="password"><br>
         <input type="submit" value="提交">
    </form>
</center>
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Servlet
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@WebServlet("/hello")
public class Servlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        String user = request.getParameter("user");
        request.setAttribute("user",user);
      request.getRequestDispatcher("/Servlet2").forward(request,response);
    }

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
 doPost(request,response);

    }
}
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Servelt2（这里要映射地址，否则会提示404 Servelt2找不到）
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@WebServlet("/Servlet2")
public class Servlet2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Object user = request.getAttribute("user");
         response.getWriter().println(user);
    }

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

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地址栏是hello 并不会显示是Servelt2