Mybatis实践教程（七）-一对一的关联关系

小鱼儿 2022-01-10 03:07 236阅读 0赞

创建一对一关系的数据表，我们在这里用丈夫和妻子的关系来表示数据库中的一对一关系，

下面我们通过实例来表示Mybatis中丈夫和妻子一对一关联关系。

需求：查询丈夫和妻子数据信息。

首先创建表结构t\_husband,t\_wife

CREATE TABLE `t_husband` (
      `id` bigint(30) NOT NULL AUTO_INCREMENT,
      `husband_name` varchar(55) DEFAULT NULL,
      `age` int(11) DEFAULT NULL,
      `wife_id` bigint(30) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;
    
      CREATE TABLE `t_wife` (
      `id` bigint(30) NOT NULL AUTO_INCREMENT,
      `wife_name` varchar(30) NOT NULL,
      `age` int(11) DEFAULT NULL,
      `hus_id` bigint(30) DEFAULT NULL,
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

创建Husband、Wife实体类

package com.example.springbootmybatis.domain;
    
    public class Husband {
        private Long id;
    
        public Long getId() {
            return id;
        }
    
        public void setId(Long id) {
            this.id = id;
        }
    
        public String getHusbandName() {
            return husbandName;
        }
    
        public void setHusbandName(String husbandName) {
            this.husbandName = husbandName;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public Long getWifeId() {
            return wifeId;
        }
    
        public void setWifeId(Long wifeId) {
            this.wifeId = wifeId;
        }
    
        public Wife getWife() {
            return wife;
        }
    
        public void setWife(Wife wife) {
            this.wife = wife;
        }
    
        private String husbandName;
        private Integer age;
        private Long wifeId;
        private Wife wife;
    
        @Override
        public String toString() {
            return "Husband{" +
                    "id=" + id +
                    ", husbandName='" + husbandName + '\'' +
                    ", age=" + age +
                    ", wifeId=" + wifeId +
                    ", wife=" + wife +
                    '}';
        }
    }

package com.example.springbootmybatis.domain;
    
    public class Wife {
        private Long id;
        private String wifeName;
    
        public Long getId() {
            return id;
        }
    
    
    
        public void setId(Long id) {
            this.id = id;
        }
    
        public String getWifeName() {
            return wifeName;
        }
    
        public void setWifeName(String wifeName) {
            this.wifeName = wifeName;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public Long getHusBandId() {
            return HusBandId;
        }
    
        public void setHusBandId(Long husBandId) {
            HusBandId = husBandId;
        }
    
        public Husband getHusband() {
            return husband;
        }
    
        public void setHusband(Husband husband) {
            this.husband = husband;
        }
    
        private Integer age;
        private Long HusBandId;
        private  Husband husband;
        @Override
        public String toString() {
            return "Wife{" +
                    "id=" + id +
                    ", wifeName='" + wifeName + '\'' +
                    ", age=" + age +
                    ", HusBandId=" + HusBandId +
                    '}';
        }
    }

HusBandService接口

package com.example.springbootmybatis.service;
    
    import com.example.springbootmybatis.domain.Husband;
    
    import java.util.List;
    
    public interface HusBandService {
    
        List<Husband> one2oneMapping();
    }

HusBandServiceImpl实现类

package com.example.springbootmybatis.service.impl;
    
    import com.example.springbootmybatis.domain.Husband;
    import com.example.springbootmybatis.mapper.HusbandMapper;
    import com.example.springbootmybatis.service.HusBandService;
    import org.springframework.stereotype.Service;
    
    import javax.annotation.Resource;
    import java.util.List;
    @Service
    public class HusbandServiceImpl implements HusBandService {
    
        @Resource
        HusbandMapper husbandMapper;
        @Override
        public List<Husband> one2oneMapping() {
            return husbandMapper.one2oneMapping();
        }
    }

HusBandServiceMapper接口

HusBandMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper
            PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
            "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    
    <mapper namespace="com.example.springbootmybatis.mapper.HusbandMapper">
        
        <resultMap id="HusbandResult" type="com.example.springbootmybatis.domain.Husband">
            <id property="id" column="id"/>
            <result property="husbandName" column="husband_name"/>
            <result property="age" column="age"/>
            <result property="wifeId" column="wife_id"/>
            
            <association property="wife">
                <result property="id" column="id" />
                <result property="wifeName" column="wife_name" />
                <result property="age" column="age" />
                <result property="husbandId" column="hus_id" />
            </association>
        </resultMap>
    
    
        
        <select id="one2oneMapping" resultMap="HusbandResult">
           select h.*,w.wife_name,w.age,w.hus_id from t_husband h left  join  t_wife w on h.wife_id = w.id
        </select>
    
    
    </mapper>

测试类

/**
     * 一对一关联关系查询
     */
    @Test
    public void one2oneMapping(){
        List<Husband> list = husBandService.one2oneMapping();
        for (Husband husbandRes:list) {
            System.out.println(husbandRes.toString());
        }
    }

执行测试类，返回结果

Husband{id=1, husbandName='zhangsan', age=25, wifeId=1, wife=Wife{id=1, wifeName='zhang wife', age=25, husBandId=1}}
    Husband{id=2, husbandName='wangwu', age=23, wifeId=2, wife=Wife{id=2, wifeName='lily', age=23, husBandId=2}}