Mybatis + mysql query to achieve two-stage cascade

Mybatis + mysql query to achieve two-stage cascade

 

First, demand: according to Mybatis achieve level 2 cascading queries.

All inquiries Municipal Information below it according to id province.

Second, the implementation steps

 

method one:

Thought: this case is " one to many ", we are one of mapper.xml in, with collection to define a collection of more than can be.

property ---> corresponding to the entity class, the subclass number, List 
ofType      ---> corresponding to the questions that subclass 
column     ----> parent key transmitted to the external subclass query 
SELECT       ----> subclass query

1. Define parent entity class + subclass

package com.imocc.mall.pojo;

import lombok.Data;

import java.util.List;

/**
 * @author wy
 */
@Data
public class Province {
    private Integer id;

    private String provinceid;

    private String province;

    private List<City> list;

    @Override
    public String toString() {
        return "Province{" +
                "id=" + id +
                ", provinceid='" + provinceid + '\'' +
                ", province='" + province + '\'' +
                ", list=" + list +
                '}';
    }
}

package com.imocc.mall.pojo;

import lombok.Data;

@Data
public class City {
    private Integer id;

    private String cityid;

    private String city;

    private String father;


}

2.mapper class

 

 2. mapperxml file

 

 3. Test

 

 

JDBC Connection [HikariProxyConnection@1532915766 wrapping com.mysql.cj.jdbc.ConnectionImpl@62dbe64e] will not be managed by Spring
==>  Preparing: select * from hat_province where provinceID =? 
==> Parameters: 110000(String)
<==    Columns: id, provinceID, province
<==        Row: 1, 110000, 北京市
====>  Preparing: select id, cityID, city, father from hat_city where father = ? 
====> Parameters: 110000(String)
<====    Columns: id, cityID, city, father
<====        Row: 1, 110100, 市辖区, 110000
<====        Row: 2, 110200, 县, 110000
<====      Total: 2
<==      Total: 1
Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@8f2098e]
Province{id=1, provinceid='110000', province='北京市', list=[City(id=1, cityid=110100, city=市辖区, father=110000), City(id=2, cityid=110200, city=县, father=110000)]}