使用mybatis建立一對一的關係

使用Hibernate用慣了的朋友，不防試着使用mybatis，mybatis比Hibernate使用起來會更加舒暢，不信我們來看看

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 1）一對一關係配置

以人和身份證爲例

實體類MyUser.java和MyCard.java

MyUser.java

package com.zking.entity;

public class MyUser{
    private int uid;//用戶編號
    private String uname;//用戶名
    private MyCard myCard;//用戶身份證


    public MyUser() {
    }

    public MyUser(int uid, String uname) {
        this.uid = uid;
        this.uname = uname;
    }

    public MyUser(int uid, String uname, MyCard myCard) {
        this.uid = uid;
        this.uname = uname;
        this.myCard = myCard;
    }

    public MyCard getMyCard() {
        return myCard;
    }

    public void setMyCard(MyCard myCard) {
        this.myCard = myCard;
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    @Override
    public String toString() {
        return "MyUser{" +
                "uid=" + uid +
                ", uname='" + uname + '\'' +
                '}';
    }
}

MyCard.java

package com.zking.entity;

public class MyCard {
    private int uid;//身份證對應的uid
    private String cnum;//身份證號

    public MyCard() {
    }

    public MyCard(int uid, String cnum) {
        this.uid = uid;
        this.cnum = cnum;
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getCnum() {
        return cnum;
    }

    public void setCnum(String cnum) {
        this.cnum = cnum;
    }

    @Override
    public String toString() {
        return "MyCard{" +
                "uid=" + uid +
                ", cnum='" + cnum + '\'' +
                '}';
    }
}

MyUser.xml配置

<?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.zking.dao.MyUserDao">
    <!--resultMap必須寫在上面，這裏配置你的返回類型-->
   <resultMap id="myUserMap" type="com.zking.entity.MyUser">
       <id property="uid" column="uid"></id>
       <result property="uname" column="uname"></result>
       <!--配對的對象在這裏設置用associatoin-->
       <association property="myCard" javaType="com.zking.entity.MyCard">
           <id property="uid" column="uid"></id>
           <result property="cnum" column="cnum"></result>
       </association>
   </resultMap>
    <!--查詢的sql，這裏的意思是以前的getsession的createQuery方法在這裏寫-->
    <!--返回的結果有關係配置於是返回的結果改爲resultMap-->
    <select id="getUserAndCardById" parameterType="int" resultMap="myUserMap">
        SELECT u.*,c.cnum from myuser u,mycard c where u.uid=c.uid AND u.uid=#{uid}
    </select>
</mapper>

還有一步

在resources中要配置你的mybatis-config.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>

    <!--設置別名-->
    <typeAliases>
        <package name="com.zking.entity"></package>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test?serverTimezone=UTC"/>
                <property name="username" value="root"/>
                <property name="password" value="1234"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/zking/entity/MyUser.xml"/>
    </mappers>
</configuration>

測試

import com.zking.dao.*;
import com.zking.dto.MyUserDto;
import com.zking.entity.*;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;
import java.util.Set;

public class TestCRUD {

    private SqlSessionFactory sqlSessionFactory;
    private SqlSession sqlSession;

    @Before
    public void before(){
        //讀取配置文件，獲取SQLSessionFactory
        String resource = "mybatis-config.xml";
        InputStream inputStream = null;
        try {
            inputStream = Resources.getResourceAsStream(resource);
            //通過SQLSessionFactory獲取SQLSession
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
            sqlSession = sqlSessionFactory.openSession();
        } catch (IOException e) {
            e.printStackTrace();
        }


    }
    @After
    public void after(){
        sqlSession.commit();
    }

public void test1(){
        MyUserDao myUserDao=sqlSession.getMapper(MyUserDao.class);
//        MyUserDto myUserDto=myUserDao.getUserAndCardById(15);
        MyUser myUser=myUserDao.getUserAndCardById(15);
        System.out.println(myUser+myUser.getMyCard().getCnum());
    }
}