6.Mybatis联合查询（一对一单条记录查询）

设计一个方法，根据pid查询这个人两个表格的所有信息
dao.PersonDao

package dao;
import domain.Person;
import org.apache.ibatis.session.SqlSession;
import util.MySqlSessionFactory;
public class PersonDao {
    private SqlSession sqlSession=MySqlSessionFactory.getSqlSession(true);
    //设计一个方法，根据pid查询这个人两个表格的所有信息
    public Person selectOne(Integer pid){
        return sqlSession.selectOne("selectOne",pid);
    }
}

domain.IDCard

package domain;
public class IDCard {
    //自有属性
    private String cardid;
    private String address;
    //为了根据身份证号查询 身份证和人的信息
    //多添加一个关联属性
    private Person person;
    public IDCard() {}
    public IDCard(String cardid, String address, Person person) {
        this.cardid = cardid;
        this.address = address;
        this.person = person;
    }
    @Override
    public String toString() {
        return "IDCard{" +
                "cardid='" + cardid + '\'' +
                ", address='" + address + '\'' +
                ", person=" + person +
                '}';
    }
    public String getCardid() {
        return cardid;
    }
    public void setCardid(String cardid) {
        this.cardid = cardid;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public Person getPerson() {
        return person;
    }
    public void setPerson(Person person) {
        this.person = person;
    }
}

domain.Person

package domain;
public class Person {
    //自有属性
    private Integer pid;
    private String pname;
    //关联属性 身份证号(身份证对象中的一个属性)
    private IDCard idcard;
    public Person() {}
    public Person(Integer pid, String pname, IDCard idcard) {
        this.pid = pid;
        this.pname = pname;
        this.idcard = idcard;
    }
    @Override
    public String toString() {
        return "Person{" +
                "pid=" + pid +
                ", pname='" + pname + '\'' +
                ", idcard=" + idcard +
                '}';
    }
    public Integer getPid() {
        return pid;
    }
    public void setPid(Integer pid) {
        this.pid = pid;
    }
    public String getPname() {
        return pname;
    }
    public void setPname(String pname) {
        this.pname = pname;
    }
    public IDCard getIdcard() {
        return idcard;
    }
    public void setIdcard(IDCard idcard) {
        this.idcard = idcard;
    }
}

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="dao.PersonDao">
    <select id="selectOne" resultMap="selectPerson">
        select pid,pname,cardid from person where pid = #{pid}
    </select>
    <!--自定义一个赋值的规则-->
    <resultMap id="selectPerson" type="domain.Person">
        <!--id一般用于主键列，result是普通列-->
        <id property="pid" column="pid"></id>
        <result property="pname" column="pname"></result>
        <association property="idcard" javaType="domain.IDCard" select="selectIdCardForPerson" column="cardid"></association>
    </resultMap>
    <!--为了Person对象中的idcard属性再次查询用-->
    <select id="selectIdCardForPerson" resultType="domain.IDCard">
        select * from idcard where cardid = #{cardid}
    </select>
</mapper>

configuration.xml

<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/testmybatis?useSSL=false&amp;characterEncoding=UTF-8"/>
                <property name="username" value="root"/>
                <property name="password" value="cy414ljh212,,,"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/PersonMapper.xml"></mapper>
    </mappers>
</configuration>

service.PersonService

package service;

import dao.PersonDao;
import domain.Person;

public class PersonService {

    private PersonDao dao = new PersonDao();

    public Person selectOne(Integer pid){
        return dao.selectOne(pid);
    }
}

test.TestMain

package test;


import service.PersonService;

public class TestMain {
    public static void main(String[] args) {
        PersonService personService=new PersonService();
        System.out.println(personService.selectOne(1));

    }
}

util.MySqlSessionFactory

package util;

import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.InputStream;

public class MySqlSessionFactory {
    //设计一个方法，获取SqlSession对象
    private static SqlSessionFactory factory;
    private static SqlSession sqlSession;
    static {
        SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
        factory = builder.build(Thread.currentThread().getContextClassLoader().getResourceAsStream("configuration.xml"));
    }

    //设计一个方法 获取sqlSession对象
    public static SqlSession getSqlSession(){
        return getSqlSession(false);
    }
    public static SqlSession getSqlSession(boolean flag){
        return factory.openSession(flag);
    }
}