登入功能我已经写好了代码如下

UserController类里面：

@RequestMapping(value = "main")
public ModelAndView main(HttpServletRequest request, User user){

ModelAndView mav = new ModelAndView();
Map<String, Object> map = new HashMap<String, Object>(); 
map.put("login", user.getLogin());//map.put得到帐号
map.put("pwd", ConvertUtils.stringToMD5(user.getPwd()));//得到密码(密码用MD5加密)

User user2 = userService.login(map); //通过User.xml登录方法判断map里面的值，值传递给UserService中判断
                                    //如果返回值是空值的话，说明请求的值在数据库中不存在
                                    //如果返回不是空值证明请求的值存在。

if(user2 != null){//返回值不是空值，登录成功
request.getSession().invalidate();//注销用户信息，request.getSession()保存用户登录信息
request.getSession().setAttribute("user", user2); //设置属性与属性值
mav.setViewName("redirect:/main.jsp");//登录成功跳转界面
operateLogService.add(request, "登录办公系统");//操作日志
} else {//返回值为空，登录失败
request.getSession().setAttribute("login", user.getLogin());
request.getSession().setAttribute("result", "登录名或密码错误");
mav.setViewName("redirect:/login.jsp");
}
return mav;
}
UserService类里面

public User login(Map<String, Object> map){
try {
return dao.login(map);
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
UserDao类里面

public User login(Map<String, Object> map);

User.xml里面

<select id="login" parameterType="Map" resultType="User">
select <include refid="field"/>
from user u
left join dept d on u.d_id = d.d_id
where u.u_login = #{login} and u.u_pwd = #{pwd} and u.u_state = 1
</select>
User类里面

@Id
@Column(name = "u_id")
@GenericGenerator(name = "idGenerator", strategy = "identity")
@GeneratedValue(generator = "idGenerator")
private Integer id;//主键

@Column(name = "u_name")
private String name;//姓名

@Column(name = "u_login")
private String login;//登录名

@Column(name = "u_pwd")
private String pwd;//登录密码

注册用户该怎么写