mybatis+oracle实现一对多，多对一查询

首先创建表

学生表

create table stu(
       id number(11) primary key,
       name varchar2(255),
       age number(11),
       cid number(11)
);

班级表

create table cls(
id number(11) primary key,
cname varchar2(255)
);

创建序列

create sequence seq_stu;

create sequence seq_cls;

添加数据

insert into stu values(seq_stu.nextval,'小乔',16,1);
insert into stu values(seq_stu.nextval,'干将',88,1);
insert into stu values(seq_stu.nextval,'鲁班',18,1);
insert into stu values(seq_stu.nextval,'婉儿',22,1);
insert into stu values(seq_stu.nextval,'艾琳',23,2);
insert into stu values(seq_stu.nextval,'安其拉',14,2);
insert into stu values(seq_stu.nextval,'牛魔',50,2);
insert into stu values(seq_stu.nextval,'猴子',66,2);
insert into stu values(seq_stu.nextval,'李白',26,1);
insert into stu values(seq_stu.nextval,'韩信',32,1);

insert into cls values (seq_cls.nextval,'QY75');
insert into cls values (seq_cls.nextval,'QY97');

创建工具类

package com.aaa.mybatis.util;

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 java.io.IOException;
import java.io.Reader;

public class SqlSessionFactoryUtil {
 private static SqlSessionFactory sessionFactory;
 static {
 Reader reader =null;
 try {
 reader= Resources.getResourceAsReader("mybatis.xml");
 /*sessionFactory =new SqlSessionFactoryBuilder().build(reader,"mysql");*/
 sessionFactory =new SqlSessionFactoryBuilder().build(reader,"myOracle");
 } catch (IOException e) {
 e.printStackTrace();
 }finally {
 try {
 reader.close();
 } catch (IOException e) {
 e.printStackTrace();
 }
 }
 }
 public static SqlSession getSession(){
 return sessionFactory.openSession();
 }
}

创建mybatis主配置文件

<?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="myOracle">
 <environment id="myOracle">
 <transactionManager type="JDBC"></transactionManager>
 <dataSource type="POOLED">
 <property name="driver" value="oracle.jdbc.driver.OracleDriver"></property>
 <property name="url" value="jdbc:oracle:thin:@localhost:1521:orcl"></property>
 <property name="username" value="scott"></property>
 <property name="password" value="tiger"></property>
 </dataSource>
 </environment>
　　　　　<--连接MySQL用下面这个,工具类加着注释-->
 <environment id="mysql">
 <transactionManager type="JDBC"></transactionManager>
 <dataSource type="POOLED">
 <property name="driver" value="com.mysql.jdbc.Driver"></property>
 <property name="url" value="jdbc:mysql://localhost:3306/test"></property>
 <property name="username" value="root"></property>
 <property name="password" value="admin"></property>
 </dataSource>
 </environment>
 </environments>

 <mappers>
 <mapper resource="com/aaa/mybatis/dao/StuDaoMapper.xml"></mapper>
 <mapper resource="com/aaa/mybatis/dao/ClsDaoMapper.xml"></mapper>
 </mappers>
</configuration>

创建Stu,Cls表实体

package com.aaa.mybatis.entity;
import java.util.*;

public class Cls {
 private int cid;
 private String cname;
 private List<Stu> stu;

 public int getCid() {
 return cid;
 }

 public void setCid(int cid) {
 this.cid = cid;
 }

 public String getCname() {
 return cname;
 }

 public void setCname(String cname) {
 this.cname = cname;
 }

 public List<Stu> getStu() {
 return stu;
 }

 public void setStu(List<Stu> stu) {
 this.stu = stu;
 }
}

package com.aaa.mybatis.entity;
public class Stu {
    private int id;
 private String name;
 private int age;
 private Cls cls;

 public int getId() {
 return id;
 }

 public void setId(int id) {
 this.id = id;
 }

 public String getName() {
 return name;
 }

 public void setName(String name) {
 this.name = name;
 }

 public int getAge() {
 return age;
 }

 public void setAge(int age) {
 this.age = age;
 }

 public Cls getCls() {
 return cls;
 }

 public void setCls(Cls cls) {
 this.cls = cls;
 }
}

创建Stu接口

package com.aaa.mybatis.dao;

import com.aaa.mybatis.entity.Stu;
import org.apache.ibatis.annotations.Param;

import java.util.*;

public interface StuDao {
 /**
 * 根据学生编号查询学生信息和班级信息
 * @param id
 * @return
 */
 
}
创建Cls接口

package com.aaa.mybatis.dao;

import com.aaa.mybatis.entity.Cls;

import java.util.*;

public interface ClsDao {
 /**
 * 根据班级编号查询该班级信息和所有学生信息
 */
 public List<Cls> allClsAndStuByCid();
}


一对多mapper根据学生编号查询学生信息和班级信息

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.aaa.mybatis.dao.StuDao">
 <resultMap id="stuMap" type="com.aaa.mybatis.entity.Stu" autoMapping="true">
 <association property="cls" javaType="com.aaa.mybatis.entity.Cls" autoMapping="true"><--autoMapping如果属性名与实体一致可以省略里面的字段-->

 </association>
 </resultMap>
 <select id="allstuByStuId" resultMap="stuMap">
 select * from stu a join cls b on a.cid=b.cid where a.id=#{id}
 </select>
</mapper>



多对一mapper查询所有班级信息和每个班的学生信息

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.aaa.mybatis.dao.ClsDao">
 <resultMap id="clsMap" type="com.aaa.mybatis.entity.Cls" autoMapping="true">
 <id column="cid" property="cid"></id><--加上autoMapping可以省略实体里字段名与属性名相同的信息，但是多对一必须在这里加ID标签-->
 <collection property="stu" ofType="com.aaa.mybatis.entity.Stu" autoMapping="true"></collection>
 </resultMap>
 <select id="allClsAndStuByCid" resultMap="clsMap">
 select * from cls a join stu b on a.cid=b.cid
 </select>
</mapper>

测试一对多

package com.aaa.mybatis.text;

import com.aaa.mybatis.dao.StuDao;
import com.aaa.mybatis.entity.Stu;
import com.aaa.mybatis.util.SqlSessionFactoryUtil;
import org.apache.ibatis.session.SqlSession;

public class text01 {
 public static void main(String[] args) {
 SqlSession session= SqlSessionFactoryUtil.getSession();
 StuDao mapper = session.getMapper(StuDao.class);
 Stu stu = mapper.allstuByStuId(6);
 System.out.println("学生姓名:"+stu.getName());
 System.out.println("学生编号:"+stu.getId());
 System.out.println("学生年龄:"+stu.getAge());
 System.out.println("班级编号:"+stu.getCls().getCid());
 System.out.println("班级名称:"+stu.getCls().getCname());
 }
}
测试结果
学生姓名:艾琳
学生编号:6
学生年龄:23
班级编号:2
班级名称:QY97

Process finished with exit code 0


测试多对一

package com.aaa.mybatis.text;

import com.aaa.mybatis.dao.ClsDao;
import com.aaa.mybatis.dao.StuDao;
import com.aaa.mybatis.entity.Cls;
import com.aaa.mybatis.entity.Stu;
import com.aaa.mybatis.util.SqlSessionFactoryUtil;
import org.apache.ibatis.session.SqlSession;

import java.util.List;

public class text02 {
 public static void main(String[] args) {
 SqlSession session= SqlSessionFactoryUtil.getSession();
 ClsDao mapper = session.getMapper(ClsDao.class);
 List<Cls> cls = mapper.allClsAndStuByCid();
 for(int i=0;i<cls.size();i++){
 System.out.println("班级编号:"+cls.get(i).getCid());
 System.out.println("班级名称:"+cls.get(i).getCname());
 System.out.println("------------------");
 List<Stu> e = cls.get(i).getStu();
 for (Stu stu : e) {
 System.out.println("学生姓名:"+stu.getName());
 System.out.println("学生编号:"+stu.getId());
 System.out.println("学生年龄:"+stu.getAge());
 System.out.println("**********************");
 }
 }

 }
}
测试结果
班级编号:1
班级名称:QY75
------------------
学生姓名:小乔
学生编号:2
学生年龄:16
**********************
学生姓名:干将
学生编号:3
学生年龄:88
**********************
学生姓名:鲁班
学生编号:4
学生年龄:18
**********************
学生姓名:婉儿
学生编号:5
学生年龄:22
**********************
学生姓名:李白
学生编号:10
学生年龄:26
**********************
学生姓名:韩信
学生编号:11
学生年龄:32
**********************
班级编号:2
班级名称:QY97
------------------
学生姓名:艾琳
学生编号:6
学生年龄:23
**********************
学生姓名:安其拉
学生编号:7
学生年龄:14
**********************
学生姓名:牛魔
学生编号:8
学生年龄:50
**********************
学生姓名:猴子
学生编号:9
学生年龄:66
**********************

Process finished with exit code 0

mybatis+oracle实现一对多，多对一查询

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