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今天需要做一个功能，根据专业，有不同的章节，章节下面有对应的习题，

由于只有这么两级，可以不用使用递归，直接查询父集，之后foreach查询子集放入对应的list集合。

虽然实现了，感觉毕竟，太low。

有同事跟我说可以使用mybatis的递归实现，就学习了下。

对应的bean里面需要有对应的list<bean> lists的引用。

直接上代码

对应的sql语句

CREATE TABLE `goods_category` (`goodscateid` int(11) NOT NULL AUTO_INCREMENT,`name` varchar(255) DEFAULT NULL,`parentid` int(11) DEFAULT NULL,`description` varchar(255) DEFAULT NULL,`displayorder` int(11) DEFAULT NULL,`commissionrate` double DEFAULT NULL,`enabled` int(11) DEFAULT NULL,PRIMARY KEY (`goodscateid`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;/*Data for the table `goods_category` */
insert  into `goods_category`(`goodscateid`,`name`,`parentid`,`description`,`displayorder`,`commissionrate`,`enabled`) values (1,'java',0,'111',NULL,NULL,NULL),(2,'spring',1,'222',NULL,NULL,NULL),(3,'springmvc',1,'333',NULL,NULL,NULL),(4,'struts',1,'444',NULL,NULL,NULL),(5,'jdbc',0,'555',NULL,NULL,NULL),(6,'hibernate',5,'666',NULL,NULL,NULL),(7,'mybatis',5,'777',NULL,NULL,NULL),(8,'jdbctemplate',5,'888',NULL,NULL,NULL),(9,'beanfactory',3,'999',NULL,NULL,NULL),(10,'factorybean',3,'000',NULL,NULL,NULL);

 实体类

@JsonIgnoreProperties({"displayorder","commissionrate","enabled"})
public class GoodsCategoryVo {private Integer goodscateid;private String name;private Integer parentid;private String description;private Integer displayorder;private Double commissionrate;private Integer enabled;private List<GoodsCategoryVo> catelist;
get 。。。 set。。。 tostring。。。

 

dao层

public interface GoodsMapper {List<GoodsCategoryVo> getCategory(Integer pid);
}

 

mapper.xml

<resultMap id="getSelf" type="com.bscc.beans.GoodsCategoryVo"><id column="goodscateid" property="goodscateid"></id><result column="name" property="name"></result><collection property="catelist" select="getCategory"column="goodscateid"></collection><!--查到的cid作为下次的pid --></resultMap><select id="getCategory" resultMap="getSelf">select * from goods_category where  parentid=#{pid}ORDER BY displayorder,goodscateid</select>

 

之后直接访问对应的方法，即可查询出来

@RequestMapping("/getGoodsList")@ResponseBodypublic List<GoodsCategoryVo> getGoodsList(){// pid指定为0List<GoodsCategoryVo> list = goodsMapper.getCategory(0);return list;}

 

结果，可以使用json在线工具

[{"goodscateid": 1,"name": "java","parentid": 0,"description": "111","catelist": [{"goodscateid": 2,"name": "spring","parentid": 1,"description": "222","catelist": []},{"goodscateid": 3,"name": "springmvc","parentid": 1,"description": "333","catelist": [{"goodscateid": 9,"name": "beanfactory","parentid": 3,"description": "999","catelist": []},{"goodscateid": 10,"name": "factorybean","parentid": 3,"description": "000","catelist": []}]},{"goodscateid": 4,"name": "struts","parentid": 1,"description": "444","catelist": []}]},{"goodscateid": 5,"name": "jdbc","parentid": 0,"description": "555","catelist": [{"goodscateid": 6,"name": "hibernate","parentid": 5,"description": "666","catelist": []},{"goodscateid": 7,"name": "mybatis","parentid": 5,"description": "777","catelist": []},{"goodscateid": 8,"name": "jdbctemplate","parentid": 5,"description": "888","catelist": []}]}
]

 

mybatis递归就是这么的简单。

 

说下mybatis一对多实现

对应的bean

public class Dept {private Integer id;private String deptName;private String locAdd;private List<Emp> emps

 

@JsonIgnoreProperties("dept")
public class Emp {private Integer id;private String name;private Dept dept;

 

dao层

public interface DeptMapper {public Dept getDeptById(Integer id);
}

public interface EmpMapper {public Emp getEmpByDeptId(Integer deptId); 
}

 

mapper.xml文件

<mapper namespace="com.bscc.mapper.DeptMapper"><resultMap id="DeptResultMap" type="com.bscc.beans.Dept"><id property="id" column="id"/><result property="deptName" column="deptName"/><result property="locAdd" column="locAdd"/><!-- private List<Emp> emps; column="id"写被集合对象主键，select按照外键键查询，通过deptid查出emp给dept-->   <collection property="emps" column="id" ofType="Emp" select="com.bscc.mapper.EmpMapper.getEmpByDeptId"/></resultMap><select id="getDeptById" parameterType="Integer" resultMap="DeptResultMap">select * from tbl_dept where id=#{id}</select>
</mapper>

 

<mapper namespace="com.bscc.mapper.EmpMapper"><resultMap  id="EmpResultMap" type="com.bscc.beans.Emp"><id property="id" column="id"/><result property="name" column="name"/></resultMap><select id="getEmpByDeptId" parameterType="Integer" resultMap="EmpResultMap">select * from tbl_emp where deptId=#{deptId}</select>
</mapper>

 

对应的controller方法

@RequestMapping("/getDeptById")@ResponseBodypublic Dept getDeptById() {Dept deptById = deptMapper.getDeptById(1);return deptById;}

 

无非就是比简单查询复杂一些罢了。

代码目录

OK！！！

 对应的github地址

https://github.com/chywx/MavenProject6oneToMany