mybatis关联查询

场景：一个人有多个手机号，一个手机号对应一个人

CREATE TABLE test.mobile
    (
    mid INT NOT NULL auto_increment,
    tel VARCHAR (50),
    pid INT,
    PRIMARY KEY (mid)
    );

CREATE TABLE test.person
    (
    pid  INT NOT NULL auto_increment,
    name VARCHAR (50),
    PRIMARY KEY (pid)
    );
INSERT INTO test.person (name)
VALUES ('wjf');
INSERT INTO test.mobile (tel, pid)
VALUES ('', 1);

INSERT INTO test.mobile (tel, pid)
VALUES ('', 1);

先上个配置文件

<?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="wjf.dao.MobileMapper">
    <resultMap type="wjf.Obj.Mobile" id="resultMap">
        <id property="mid" column="mid" />
        <result property="tel" column="tel" />
        <association property="person" javaType="wjf.Obj.Person"
            column="pid">
            <id property="pid" column="pid" />
            <result property="name" column="name" />
        </association>
    </resultMap>
    <select id="getMobile" parameterType="int" resultMap="resultMap">
        select
        p.pid,p.name ,m.mid ,m.tel
        from person p ,mobile m where m.pid=p.pid
        AND m.mid=#{id}
    </select>
    <select id="getALLMobile" resultMap="resultMap">
        select
        p.pid,p.name ,m.mid
        ,m.tel
        from person p ,mobile m where m.pid=p.pid
    </select>
</mapper>    

<?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="wjf.dao.PersonMapper">
    <resultMap type="wjf.Obj.Person" id="resultMap">
        <id property="pid" column="pid" />
        <result property="name" column="name" />
        <collection property="mobiles" column="pid" ofType="wjf.Obj.Mobile">
            <id property="id" column="mid" />
            <result property="tel" column="tel" />
        </collection>
    </resultMap>

    <select id="getPerson" parameterType="int" resultMap="resultMap">
        select
        p.pid,p.name ,m.mid ,m.tel
        from person p ,mobile m where m.pid=p.pid
        AND p.pid=#{id}
    </select>
    <select id="getALLPerson" resultMap="resultMap">
        select
        p.pid,p.name ,m.mid
        ,m.tel
        from person p ,mobile m where m.pid=p.pid
    </select>
</mapper>    

再上个对象

package wjf.Obj;

import java.util.List;

public class Person {
    private int pid;
    private String name;
    private List<Mobile> mobiles;
    public List<Mobile> getMobiles() {
        return mobiles;
    }
    public void setMobiles(List<Mobile> mobiles) {
        this.mobiles = mobiles;
    }
    public int getId() {
        return pid;
    }
    public void setId(int id) {
        this.pid = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    @Override
    public String toString() {
        return "Person [id=" + pid + ", name=" + name + "]";
    }
}

package wjf.Obj;

public class Mobile {
    private int mid;
    private String tel;
    private Person person;
    /**
     * @return the mid
     */
    public int getMid() {
        return mid;
    }
    /**
     * @param mid the mid to set
     */
    public void setMid(int mid) {
        this.mid = mid;
    }
    /**
     * @return the person
     */
    public Person getPerson() {
        return person;
    }
    /**
     * @param person the person to set
     */
    public void setPerson(Person person) {
        this.person = person;
    }
    public int getId() {
        return mid;
    }
    public void setId(int id) {
        this.mid = id;
    }
    public String getTel() {
        return tel;
    }
    public void setTel(String tel) {
        this.tel = tel;
    }
    @Override
    public String toString() {
        return "Mobile [id=" + mid + ", tel=" + tel + "]";
    }
}

上个映射类

package wjf.dao;

import java.util.List;

import wjf.Obj.Mobile;

public interface MobileMapper {
    public Mobile getMobile(int id);

    public List<Mobile> getALLMobile();
}

package wjf.dao;

import java.util.List;
import wjf.Obj.Person;

public interface PersonMapper {
    public Person getPerson(int id);

    public List<Person> getALLPerson();
}

最后就是mybatis的配置了

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <typeAliases>
        <typeAlias alias="UserInfo" type="wjf.orm.UserInfo"/>
    </typeAliases>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC" />
            <!-- 配置数据库连接信息 -->
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver" />
                <property name="url" value="jdbc:mysql://localhost:3306/test" />
                <property name="username" value="root" />
                <property name="password" value="123" />
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <!-- <mapper resource="wjf/orm/userMapper.xml"/> -->
        <!-- <mapper resource="wjf/orm/userMapper2.xml"/> -->
        <mapper resource="wjf/config/MobileMapper.xml"/>
        <mapper resource="wjf/config/PersonMapper.xml"/>
    </mappers>
</configuration>

测试程序如下

    @Test
    public void testRelation() {
        SqlSessionFactory sqlSessionFactory = MybatisUtil
                .getSqlsessionfactory();
        SqlSession sqlSession = null;
        sqlSession = sqlSessionFactory.openSession();
//        PersonMapper pmapper = sqlSession.getMapper(PersonMapper.class);
//        List<Person> plist = pmapper.getALLPerson();
//        System.out.println(plist.size());
//        Person p = pmapper.getPerson(1);
//        System.out.println(p.getMobiles().size());

        MobileMapper mmapper = sqlSession.getMapper(MobileMapper.class);
        List<Mobile> pMobile = mmapper.getALLMobile();
        System.out.println(pMobile.size());
        Mobile m = mmapper.getMobile(1);
        System.out.println(m.getPerson().getName());
    }

补上一个mybatis封装类

package wjf.orm;

import java.io.Reader;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

//工具类
public class MybatisUtil {
    public static SqlSessionFactory sqlSessionFactory() {

        String resource = "config.xml";// 获取mybatis-cofig.xml配置文件的路径
        Reader reader = null;// 创建reader
        try {
            reader = Resources.getResourceAsReader(resource);// 获得reader
        } catch (Exception e) {
            // TODO: handle exception
            e.printStackTrace();
        }
        SqlSessionFactory SqlSessionFactory = new SqlSessionFactoryBuilder()
                .build(reader);// 获得sqlsessionfactory
        return SqlSessionFactory;
    }

    // 获取getter
    public static SqlSessionFactory getSqlsessionfactory() {
        return sqlSessionFactory();
    }

}