Mybatis一对一

0.前期准备

数据库配置：

CREATE TABLE tb_card
(
  id   INT AUTO_INCREMENT
    PRIMARY KEY,
  code VARCHAR(18) NULL,
  CONSTRAINT tb_card_id_uindex
  UNIQUE (id)
)

CREATE TABLE tb_person
(
  id      INT AUTO_INCREMENT
    PRIMARY KEY,
  name    VARCHAR(18) NULL,
  sex     VARCHAR(18) NULL,
  age     INT         NULL,
  card_id INT         NULL,
  CONSTRAINT tb_person_id_uindex
  UNIQUE (id),
  CONSTRAINT tb_person_card_id_uindex
  UNIQUE (card_id),
  CONSTRAINT tb_person_tb_card_id_fk
  FOREIGN KEY (card_id) REFERENCES tb_card (id)
)
  ENGINE = Inno

身份证和人是一对一的关系，在tb_person表中，card_id为外键，对应tb_card主键，且card_id唯一，就满足了一对一的关系。

2.POJO类

两个pojo类：

public class Card implements Serializable{

 private Integer id;
 private String code;
 //getter，setter

public class Person implements Serializable{

 private Integer id;
 private String name;
 private String sex;
 private Integer age;
 private Card card;
 //getter,setter

3.mapper和mybatis-config.xml配置

mapper配置：

//CardMapper.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="org.fkit.mapper.CardMapper">
    <select id="selectCardById" parameterType="int" resultType="org.fkit.domain.Card">
        SELECT * FROM tb_card WHERE id = #{id}
    </select>
</mapper>

//PersonMapper.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="org.fkit.mapper.PersonMapper">
    <select id="selectPersonById" parameterType="int" resultMap="personMapper">
          select * from tb_person where id = #{id}
    </select>
    <resultMap id="personMapper" type="org.fkit.domain.Person">
        <id property="id" column="id"/>
        <result property="name" column="name"/>
        <result property="sex" column="sex"/>
        <result property="age" column="age"/>
        <association property="card" column="card_id"
                     select="org.fkit.mapper.CardMapper.selectCardById"
                     javaType="org.fkit.domain.Card"/>
    </resultMap>
</mapper>

在此可以给PersonMapper设置一个接口：

//PersonMapper.java
package org.fkit.mapper;

import org.fkit.domain.Person;

public interface PersonMapper {
    /**
     * @param id
     * @return Person
     */
    Person selectPersonById(Integer id);
}

在mybatis-config.xml中配置这2个mapper：

<mapper resource="org/fkit/mapper/PersonMapper.xml"/>
<mapper resource="org/fkit/mapper/CardMapper.xml"/>

4.测试

测试代码：

//OneToOneTset.java
public class OneToOneTest {
    public static void main(String args[])throws Exception {
        SqlSession sqlSession = FKSqlSessionFactory.getSqlSession();
        Person person = sqlSession.selectOne("org.fkit.mapper.PersonMapper.selectPersonById", 1);
        System.out.println(person);
    }
}
//output:
Person{id=1, name='jack', sex='男', age=23, card=Card{id=1, code='432801198009191038'}}

因为设置了接口，也可以如此测试：

//OneToOneTset.java

public class OneToOneTest {
    public static void main(String args[])throws Exception {
        InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        SqlSession session = sqlSessionFactory.openSession();
        PersonMapper personMapper = session.getMapper(PersonMapper.class);
        Person person = personMapper.selectPersonById(1);
        System.out.println(person);
    }
}

//output:
Person{id=1, name='jack', sex='男', age=23, card=Card{id=1, code='432801198009191038'}}