前言

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

结果，可以使用json在线工具，也可以使用这个工具

[ { "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") @ResponseBody public 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（本地下载）

总结

以上就是这篇文章的全部内容了，希望本文的内容对大家的学习或者工作具有一定的参考学习价值，如果有疑问大家可以留言交流，谢谢大家对的支持。