Java中MapStruct的使用详解

        <dependency>
            <groupId>org.mapstruct</groupId>
            <artifactId>mapstruct</artifactId>
            <version>1.4.2.Final</version>
        </dependency>

@Data
@NoArgsConstructor
@AllArgsConstructor
public class User {
    private String id;
    private String name;
    private Date crateTime;
}

@Data
@NoArgsConstructor
@AllArgsConstructor
public class UserDto {
    private String userId;
    private String userName;
    private Date beginTime;
}

/**
 * componentModel 制定模式spring  将bean交给spring管理
 * unmappedTargetPolicy ignore 目标属性未匹配时系统忽略，不打印警告日志
 */
@Mapper(componentModel = "spring", unmappedTargetPolicy = ReportingPolicy.IGNORE )
public interface UserMapper {
    //静态成员
    UserMapper INSTANCE = Mappers.getMapper(UserMapper.class);
    // 单个书写
    // 常量
    @Mapping(source = "id", target = "userId",constant = "可以指定常量")
    // 默认值
    @Mapping(source = "name", target = "userName", defaultValue = "可以指定默认值")
    // 日期转换
    @Mapping(source = "crateTime", target = "beginTime", dateFormat = "yyyy-MM-dd HH:mm:ss")
    UserDto userToUserDto(User user);
    // 批量写法 与上述二选一
    @Mappings({
            // Integer 到 String的转换
            @Mapping(source = "id", target = "numId" ,numberFormat = "$#.00"),
            @Mapping(source = "name", target = "userName"),
            //Date 转字符串
            @Mapping(source = "crateTime", target = "crtTime", dateFormat = "dd.MM.yyyy"),
            // 使用java可执行代码或函数
            @Mapping(target = "crateTime", expression = "java(java.time.LocalDateTime.now()")
    })
    UserDto userToUserDto2(User user);
    // 批量转换,循环调用上面单个转换
    List<UserDto> userToUserDtoList(List<User> users);
}

@Component
public class UserMapperImpl implements UserMapper {
    public UserMapperImpl() {
    }
    @Override
    public UserDto userToUserDto(User user) {
        if (user == null){
            return null;
        }else{
            UserDto userDto = new UserDto();
            user.setId(user.getId());
            user.setName(user.getName());
            user.setCrateTime(user.getCrateTime());
            return userDto;
        }
    }
    @Override
    public List<UserDto> userToUserDtoList(List<User> users) {
        if (users == null){
            return null;
        }else{
            List<UserDto> list = new ArrayList<>(users.size());
            Iterator var3 = users.iterator();
            while (var3.hasNext()){
                User user = (User) var3.next();
                list.add(this.userToUserDto(user));
            }
            return list;
        }
    }
}