管理员修改用户信息(2课时流程讲解+学员上来演示，1课时全体学生练习)
step1 根据id查询用户信息 返回一个user
userlist.jsp页面:

<a href="<%=request.getContextPath()%>/getUserServlet?id=${user.id }">修改</a>

GetUserServlet

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setCharacterEncoding("utf-8");
        //获取页面传过来的id
        String id=request.getParameter("id");
        IUserService service=new UserServiceImpl();
        User user=service.getUserById(id);
        request.setAttribute("user", user);
        request.getRequestDispatcher("/admin/updateuser.jsp").forward(request, response);;
        
    }

/admin/updateuser.jsp

<form action="<%=request.getContextPath()%>/adminUpdServlet">
   <input type="hidden" name="id" value="${user.id }"/>
   用户名：<input type="text" name="userName" value="${user.userName }" readonly/><br>
 email：<input type="email" name="email" value="${user.email }"/><br>
 idCard：<input type="text" name="idCard" value="${user.idCard }"/><br>
 用户权限：<select name="power">
 <option value="0" <c:if test="${user.power==0 }">selected="selected"</c:if>>普通用户</option>
 <option value="1" <c:if test="${user.power==1 }">selected="selected"</c:if>>管理员</option>
 </select>
 <input type="submit" value="修改"/>
 <input type="reset"/>
</form>

step2 提交修改后的表单，进行update
adminUpdServlet.java

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取前台页面传过来的参数
        String id=request.getParameter("id");
        String name=request.getParameter("userName");
        String email=request.getParameter("email");
        String idCard=request.getParameter("idCard");
        String power=request.getParameter("power");
        //封装user对象
        User user=new User();
        user.setId(Integer.parseInt(id));
        user.setUserName(name);
        user.setEmail(email);
        user.setIdCard(idCard);
        user.setPower(Integer.parseInt(power));
        //调用service进行修改操作
        IUserService service=new UserServiceImpl();
        int i=service.update(user);
        response.sendRedirect(request.getContextPath()+"/findAllUserServlet");
    }

作业：管理员添加用户信息