MapStruct使用技巧

　　在设计数据库时，往往会增加一个字段features varchar（1000），用来做扩展字段，避免改表结构的。尤其是针对给某一条记录进行”打标操作“。

那么，在DO类转为域模型对象时就有一个转换问题。

　　下面介绍使用mapstruct优雅的进行转换

　　

package com.chinaunicom.base.server.converter;

import com.chinaunicom.base.domain.model.userspace.UserSpace;
import com.chinaunicom.base.server.converter.worker.UserSpaceConvert;
import com.chinaunicom.base.server.dao.datamodel.UserSpaceEntity;
import org.mapstruct.Mapper;
import org.mapstruct.Mapping;
import org.mapstruct.Mappings;
import org.mapstruct.factory.Mappers;

import java.util.List;

@Mapper(componentModel = "spring", uses = {UserSpaceConvert.class})
public interface UserSpaceBaseConverter {
    UserSpaceBaseConverter INSTANCES = Mappers.getMapper(UserSpaceBaseConverter.class);

    @Mappings({
            @Mapping(source = "id", target = "id"),
            @Mapping(source = "employeeName", target = "employeeName"),
            @Mapping(source = "rootSpace", target = "rootSpace"),
            @Mapping(source = "createTime", target = "createTime"),
            @Mapping(source = "deleted", target = "deleted")
    })
    UserSpaceEntity to(UserSpace userSpace);

    @Mappings({
            @Mapping(source = "id", target = "id"),
            @Mapping(source = "employeeName", target = "employeeName"),
            @Mapping(source = "rootSpace", target = "rootSpace"),
            @Mapping(source = "createTime", target = "createTime"),
            @Mapping(source = "deleted", target = "deleted"),
            @Mapping(target = "age", expression = "java(com.chinaunicom.base.server.converter.worker.UserSpaceConvert.getAgeFromFeatures(userSpaceEntity.getFeatures()))")
    })
    UserSpace back(UserSpaceEntity userSpaceEntity);

    List<UserSpaceEntity> toList(List<UserSpace> source);

    List<UserSpace> backList(List<UserSpaceEntity> source);
}

　　UserSpaceEntity 

public class UserSpaceEntity {
    private Integer id;
    private String employeeName;
    private String rootSpace;
    private Date createTime;
    private Integer deleted;//1 删除 0 未删除
    private String features;

}

　　UserSpace

public class UserSpace implements Serializable {

    private Integer id;

    private String employeeName;

    private String rootSpace;

    private Date createTime;

    private Integer deleted = 0;

    private Integer age;
}

　　其中 UserSpaceEntity 的features是保存的JSON格式数据，数据库中也是JSON

public class UserSpaceConvert {

    public static Integer getAgeFromFeatures(String json) {
        Map<String,Object> valueMap = JSON.parseObject(json, Map.class);
        if (valueMap.containsKey("age")) {
            return Integer.valueOf(valueMap.get("age").toString());
        }

        return null;
    }
}