MyBatis3.X复杂Sql查询
MyBatis3.X的resultMap
1.Mybatis的sql语句返回的结果有两种
- resultType
- 查询出的字段在相应的pojo中必须有和它相同的字段对应,或者基本数据类型
- 适合简单查询
- resultMap
需要自定义字段,或者多表查询,一对多等关系,比resultType更强大
适合复杂查询
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<resultMap id= "VideoResultMap" type= "Video" > <! -- id 指定查询列列的唯⼀一标示 column 数据库字段的名称 property pojo类的名称 --> <id column = "id" property= "id" jdbcType= "INTEGER" /> <result column = "video_tile" property= "title" jdbcType= "VARCHAR" /> <result column = "summary" property= "summary" jdbcType= "VARCHAR" /> <result column = "cover_img" property= "coverImg" jdbcType= "VARCHAR" /> </resultMap> < select id= "selectBaseFieldByIdWithResultMap" resultMap= "VideoResultMap" > select id , title as video_tile, summary, cover_img from video where id = #{video_id} </ select > |
ResultMap复杂对象一对一查询结果映射之association
association:映射到POJO的某个复杂类型属性,比如订单order对象里面包含user对象
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<!-- 名称空间,需要保存全局唯一,最好是和dao层的Java接口一致 可以映射sql语句到对应的方法名参数和返回值 mybatis是使用接口动态代理 --> <mapper namespace= "net.xiaotiancai.online_class.dao.VideoOrderMapper" > <resultMap id= "VideoOrderResultMap" type= "VideoOrder" > <id column= "id" property= "id" ></id> <result column= "user_id" property= "userId" ></result> <result column= "out_trade_no" property= "outTradeNo" ></result> <result column= "state" property= "state" ></result> <result column= "total_fee" property= "totalFee" ></result> <result column= "video_id" property= "videoId" ></result> <result column= "video_title" property= "videoTitle" ></result> <!-- 配置属性一对一 property对应videoOrder里面的User javaType对应这个属性的类型 --> <association property= "user" javaType= "User" > <id column= "user_id" property= "id" ></id> <result column= "name" property= "name" ></result> <result column= "head_img" property= "headImg" ></result> <result column= "phone" property= "phone" ></result> </association> </resultMap> <!--一对一订单查询,订单内部包含用户属性--> <select id= "queryVideoOrderList" resultMap= "VideoOrderResultMap" > select o.id id, o.user_id, o.out_trade_no, o.state, o.total_fee, o.video_id, o.video_title, u.name, u.head_img, u.phone from video_order o left join user u on o.user_id = u.id </select> </mapper> |
代码
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// resultmap association关联查询 VideoOrderMapper videoOrderMapper =sqlSession.getMapper(VideoOrderMapper. class ); List<VideoOrder> videoOrderList = videoOrderMapper.queryVideoOrderList(); System.out.println(videoOrderList.toString()); |
ResultMap复杂对象一对多查询结果映射之collection
collection: 一对多查询结果查询映射,比如user有多个订单
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<resultMap id= "UserOrderResultMap" type= "User" > <id property= "id" column= "id" /> <result property= "name" column= "name" /> <result property= "headImg" column= "head_img" /> <result property= "phone" column= "phone" /> <!-- property 填写pojo类中集合类属性的名称 ofType 集合⾥里里⾯面的pojo对象 --> <collection property= "videoOrderList" ofType= "VideoOrder" > <!--配置主键,管理理order的唯⼀一标识--> <id column= "order_id" property= "id" /> <result column= "user_id" property= "userId" /> <result column= "out_trade_no" property= "outTradeNo" /> <result column= "state" property= "state" /> <result column= "total_fee" property= "totalFee" /> <result column= "video_id" property= "videoId" /> <result column= "video_title" property= "videoTitle" /> <result column= "video_img" property= "videoImg" /> </collection> </resultMap> <select id= "queryUserOrder" resultMap= "UserOrderResultMap" > select u.id, u.name, u.head_img, u.phone, o.id order_id, o.out_trade_no, o.user_id, o.state, o.total_fee, o.video_id, o.video_title from user u left join video_order o on u.id = o.user_id </select> |
代码
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// resultmap association关联查询 VideoOrderMapper videoOrderMapper =sqlSession.getMapper(VideoOrderMapper. class ); //resultmap collection测试 List<User> userList = videoOrderMapper.queryUserOrder(); System.out.println(userList.toString()); |
Mybatis3.X ResultMap复杂对象查询总结
总结ResultMap的复杂对象查询
- association映射的是一个pojo类,处理一对一的关联关系。
- collection映射的一个集合列表,处理的是一对多的关联关系。
- 模板
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<!--column不做限制,可以为任意表的字段,而property须为type定义的pojo属性--> <resultMap id=“唯一的标识”type=“映射的pojo对象"> <id column= "表的主键字段,或查询语句中的别名字段”jdbcrype=" 字段类型”property=“映射pojo对象的主键属性"/> <result column= "表的一个字段”jdbcrype=" 字段类型”property=“映射到pojo对象的一个属性"/> <association property= "pojo的一个对象属性”javarype=" pojo关联的pojo对象"> <id column= "关联pojo对象对应表的主键字段”jdbcrype=" 字段类型”property= "关联pojo对象的属性" /> <result column= "表的字段”jdbcrype=" 字段类型”property= "关联pojo对象的属性" /> </association> <!--集合中的property 需要为oftype定义的pojo对象的属性--> <collection property= "pojo的集合属性名称”ofType=" 集合中单个的pojo对象类型"> <id column= "集合中pojo对象对应在表的主键字段”jdbcrype=" 字段类型”property=“集合中pojo对象的主键属性”/> <result column= "任意表的字段”jdbcrype=" 字段类型”property="集合中的pojo对象的属性”/> </collection> </resultMap> |
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原文链接:https://blog.csdn.net/ruan_luqingnian/article/details/115366923