使用mybatis建立一对一的关系

使用Hibernate用惯了的朋友，不防试着使用mybatis，mybatis比Hibernate使用起来会更加舒畅，不信我们来看看

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 1）一对一关系配置

以人和身份证为例

实体类MyUser.java和MyCard.java

MyUser.java

package com.zking.entity;public class MyUser{    private int uid;//用户编号    private String uname;//用户名    private MyCard myCard;//用户身份证    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;//身份证对应的uid    private String cnum;//身份证号    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必须写在上面，这里配置你的返回类型-->   <resultMap id="myUserMap" type="com.zking.entity.MyUser">       <id property="uid" column="uid"></id>       <result property="uname" column="uname"></result>       <!--配对的对象在这里设置用associatoin-->       <association property="myCard" javaType="com.zking.entity.MyCard">           <id property="uid" column="uid"></id>           <result property="cnum" column="cnum"></result>       </association>   </resultMap>    <!--查询的sql，这里的意思是以前的getsession的createQuery方法在这里写-->    <!--返回的结果有关系配置于是返回的结果改为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>

还有一步

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>    <!--设置别名-->    <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>

测试

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(){        //读取配置文件，获取SQLSessionFactory        String resource = "mybatis-config.xml";        InputStream inputStream = null;        try {            inputStream = Resources.getResourceAsStream(resource);            //通过SQLSessionFactory获取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());    }}