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DTO、VO、POJO与实体类使用方案（结合Mapper.xml）

news 来源：原创 2025/6/26 12:03:53

结合MyBatis的Mapper.xml文件，展示完整的层级数据流转和数据库操作。

1. 实体类优化（Entity）

// User.java
@Data
@NoArgsConstructor
@AllArgsConstructor
@TableName("sys_user")
public class User {@TableId(type = IdType.AUTO)private Long userId;@NotBlankprivate String username;@NotBlankprivate String password;private String email;private String phone;private Date createTime;// 非数据库字段，用于关联查询@TableField(exist = false)private List<Role> roles;
}// Role.java
@Data
@TableName("sys_role")
public class Role {@TableId(type = IdType.AUTO)private Long roleId;private String roleName;private String roleDesc;
}

2. Mapper接口与XML配置

UserMapper.java

@Mapper
public interface UserMapper {// 插入用户并返回主键int insertUser(User user);// 根据ID查询用户（包含角色信息）User selectUserWithRoles(@Param("userId") Long userId);// 分页查询用户List<User> selectUserList(UserQueryDTO queryDTO);// 批量插入用户角色关系int batchInsertUserRoles(@Param("list") List<UserRole> userRoles);
}

UserMapper.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" 
"http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.example.mapper.UserMapper"><!-- 基本结果映射 --><resultMap id="BaseUserMap" type="com.example.entity.User"><id column="user_id" property="userId"/><result column="username" property="username"/><result column="password" property="password"/><result column="email" property="email"/><result column="phone" property="phone"/><result column="create_time" property="createTime"/></resultMap><!-- 包含角色信息的用户映射 --><resultMap id="UserWithRolesMap" type="com.example.entity.User" extends="BaseUserMap"><collection property="roles" ofType="com.example.entity.Role"><id column="role_id" property="roleId"/><result column="role_name" property="roleName"/><result column="role_desc" property="roleDesc"/></collection></resultMap><!-- 插入用户 --><insert id="insertUser" useGeneratedKeys="true" keyProperty="userId">INSERT INTO sys_user (username, password, email, phone)VALUES (#{username}, #{password}, #{email}, #{phone})</insert><!-- 查询用户及其角色 --><select id="selectUserWithRoles" resultMap="UserWithRolesMap">SELECT u.*, r.role_id, r.role_name, r.role_descFROM sys_user uLEFT JOIN sys_user_role ur ON u.user_id = ur.user_idLEFT JOIN sys_role r ON ur.role_id = r.role_idWHERE u.user_id = #{userId}</select><!-- 动态查询用户列表 --><select id="selectUserList" resultMap="BaseUserMap">SELECT * FROM sys_user<where><if test="username != null and username != ''">AND username LIKE CONCAT('%', #{username}, '%')</if><if test="email != null and email != ''">AND email = #{email}</if><if test="phone != null and phone != ''">AND phone = #{phone}</if><if test="createTimeStart != null">AND create_time >= #{createTimeStart}</if><if test="createTimeEnd != null">AND create_time &lt;= #{createTimeEnd}</if></where>ORDER BY create_time DESC</select><!-- 批量插入用户角色关系 --><insert id="batchInsertUserRoles">INSERT INTO sys_user_role (user_id, role_id)VALUES<foreach collection="list" item="item" separator=",">(#{item.userId}, #{item.roleId})</foreach></insert>
</mapper>

3. 服务层优化实现

@Service
@RequiredArgsConstructor
public class UserServiceImpl implements UserService {private final UserMapper userMapper;private final RoleMapper roleMapper;private final PasswordEncoder passwordEncoder;@Override@Transactionalpublic UserVO createUser(UserDTO userDTO) {// DTO转EntityUser user = new User();BeanUtils.copyProperties(userDTO, user);// 密码加密user.setPassword(passwordEncoder.encode(userDTO.getPassword()));// 保存用户userMapper.insertUser(user);// 保存用户角色关系if (!CollectionUtils.isEmpty(userDTO.getRoleIds())) {List<UserRole> userRoles = userDTO.getRoleIds().stream().map(roleId -> new UserRole(user.getUserId(), roleId)).collect(Collectors.toList());userMapper.batchInsertUserRoles(userRoles);}// 返回完整的用户信息return getUserVO(user.getUserId());}@Overridepublic PageVO<UserVO> getUsers(UserQueryDTO queryDTO) {// 设置分页参数PageHelper.startPage(queryDTO.getPageNum(), queryDTO.getPageSize());// 查询用户列表List<User> users = userMapper.selectUserList(queryDTO);PageInfo<User> pageInfo = new PageInfo<>(users);// 转换为VO列表List<UserVO> userVOs = users.stream().map(user -> UserVO.fromEntity(user, getRolesByUserId(user.getUserId()))).collect(Collectors.toList());// 构建分页VOreturn new PageVO<>(pageInfo.getTotal(),pageInfo.getPageNum(),pageInfo.getPageSize(),userVOs);}@Overridepublic UserVO getUserVO(Long userId) {User user = userMapper.selectUserWithRoles(userId);return UserVO.fromEntity(user, user.getRoles());}private List<Role> getRolesByUserId(Long userId) {return roleMapper.selectByUserId(userId);}
}

4. DTO/VO优化设计

UserDTO.java

@Data
public class UserDTO {@NotBlank(message = "用户名不能为空")@Size(min = 4, max = 20)private String username;@NotBlank(message = "密码不能为空")@Size(min = 6, max = 20)@Pattern(regexp = "^(?=.*[A-Za-z])(?=.*\\d).*$", message = "密码必须包含字母和数字")private String password;@Emailprivate String email;@Pattern(regexp = "^1[3-9]\\d{9}$")private String phone;@NotEmpty(message = "至少分配一个角色")private List<Long> roleIds;// 自定义转换方法public User toEntity() {User user = new User();BeanUtils.copyProperties(this, user);return user;}
}

UserVO.java

@Data
@Accessors(chain = true)
public class UserVO {private Long userId;private String username;private String email;private String phone;@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")private Date createTime;private List<RoleVO> roles;// 静态工厂方法public static UserVO fromEntity(User user, List<Role> roles) {return new UserVO().setUserId(user.getUserId()).setUsername(user.getUsername()).setEmail(user.getEmail()).setPhone(user.getPhone()).setCreateTime(user.getCreateTime()).setRoles(roles.stream().map(RoleVO::fromEntity).collect(Collectors.toList()));}
}

PageVO.java (通用分页VO)

@Data
@AllArgsConstructor
public class PageVO<T> {private Long total;private Integer pageNum;private Integer pageSize;private List<T> list;// 计算总页数public Integer getPages() {if (pageSize == 0) return 0;return (int) Math.ceil((double) total / pageSize);}
}

5. 控制器层优化

@RestController
@RequestMapping("/api/users")
@RequiredArgsConstructor
public class UserController {private final UserService userService;@PostMappingpublic ResponseEntity<Result<UserVO>> createUser(@Valid @RequestBody UserDTO userDTO) {UserVO userVO = userService.createUser(userDTO);return ResponseEntity.ok(Result.success(userVO));}@GetMappingpublic ResponseEntity<Result<PageVO<UserVO>>> getUsers(@Valid UserQueryDTO queryDTO) {PageVO<UserVO> page = userService.getUsers(queryDTO);return ResponseEntity.ok(Result.success(page));}@GetMapping("/{userId}")public ResponseEntity<Result<UserVO>> getUser(@PathVariable Long userId) {UserVO userVO = userService.getUserVO(userId);return ResponseEntity.ok(Result.success(userVO));}
}// 通用返回结果
@Data
@AllArgsConstructor
class Result<T> {private int code;private String message;private T data;public static <T> Result<T> success(T data) {return new Result<>(200, "success", data);}
}