详解mybatis关系映射之一对多和多对一

 CREATE DATABASE test;  
  USE test; 
  CREATE TABLE person( 
   personId VARCHAR(36) PRIMARY KEY, 
   personName VARCHAR(64), 
   personAddress VARCHAR(128), 
   personTel VARCHAR(11) 
  ); 
  CREATE TABLE orders( 
   orderId VARCHAR(36) PRIMARY KEY, 
   orderNumber VARCHAR(20), 
   orderPrice INT, 
   pid VARCHAR(36) 
  ); 
INSERT INTO person VALUES('1', '木子', '湖北', '110'); 
INSERT INTO person VALUES('2', '木子大大', '武汉', '120'); 
INSERT INTO person VALUES('1', '木子苗苗', '天门', '119'); 
  INSERT INTO orders VALUES('1', '001', 100, '1'); 
  INSERT INTO orders VALUES('2', '002', 200, '1'); 
  INSERT INTO orders VALUES('3', '003', 300, '2'); 
  INSERT INTO orders VALUES('4', '004', 400, '2'); 
  INSERT INTO orders VALUES('5', '005', 500, '3'); 
SELECT p.*, o.* FROM person p JOIN orders o ON (p.personId=o.pid) WHERE p.personId = '1' ;
*指显示所有字段

package com.mybatis.domain;
import java.util.List;
import lombok.Data;
@Data//注释（Person为单方）
public class Person {
  private String personid;
  private String personname;
  private String personaddress;
  private String persontel;
  //这个代表多方里面的内容（Orders）
  private List orders;
 @Override
 public String toString() {
 return "Person [personid=" + personid + ", personname=" + personname
  + ", personaddress=" + personaddress + ", persontel="
  + persontel + ", orders=" + orders + "]";
 }
}

package com.mybatis.domain;
import lombok.Data;
@Data//（Orders为多方）
public class Orders {
  private String orderid;
  private String ordernumber;
  private Integer orderprice;
  //对象（单方Person）与外键进行关联
  private Person person;
}

package com.mybatis.dao.mapper;
import com.mybatis.domain.Orders;
import com.mybatis.domain.Person;
import java.util.List;
public interface PersonMapper {
  int deleteByPrimaryKey(String personid);
  int insert(Person record);
  Person selectByPrimaryKey(String personid);
  List selectAll();
  int updateByPrimaryKey(Person record);
  //一对多查询(根据id查询)
  public List findPersonAndOrders(String pid);
  //一对多查询返回一个对象
  public Person selectPersonById(String id);
}

<?xml version="1.0" encoding="UTF-8" ?>


 
  
  
  
  
  
     
     
     
       
      
       
       
     
 
   
   
    SELECT p.*,o.* FROM person o,orders b WHERE o.personid=#{pid};
   
    
    select p.*, o.* from person p, orders o where p.personId = o.pid and p.personId = #{id} 
   
 

package com.mybatis.dao.mapper;
import com.mybatis.domain.Orders;
import java.util.List;
public interface OrdersMapper {
  int deleteByPrimaryKey(String orderid);
  int insert(Orders record);
  Orders selectByPrimaryKey(String orderid);
  List selectAll();
  int updateByPrimaryKey(Orders record);
  //多查一 根据id
  public Orders selectOrderById(String oid);
  //多查一 根据orderNumber
  public Orders selectOrderNumber(String number);
}

<?xml version="1.0" encoding="UTF-8" ?>


 
  
  
  
  
    
     
     
      
  
 
 
 

 
 

 select p.*, o.* from person p, orders o where p.personId = o.pid and o.orderId = #{oid}
 
 

select p.*, o.* from person p, orders o where p.personId = o.pid and o.orderId = #{number}
 

db.properties配置（sql语句的基本链接）
db.driver=com.MySQL.jdbc.Driver
db.url=jdbc:mysql://localhost:3306/wang1?useUnicode=true&characterEncoding=utf8
db.username=root
db.password=123456
   log4j.properties配置（注释）
# Global logging configuration
log4j.rootLogger=DEBUG, stdout
# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n
  mybatis.xml（逆向生成domain、dao层）
<?xml version="1.0" encoding="UTF-8" ?>



 
 
 
 
   
 
 
 
 
 
 
  
  
  
  
  
  
  
  
  
 
 
 
   
 
 
  

  generatorConfig.xml配置（对MySQL进行操作）下面标红部分根据自己建立的进行修改
<?xml version="1.0" encoding="UTF-8"?>


  D盘中要有此包mysql-connector-java-5.1.7-bin.jar

 
 
 
 
 
 
 
 
 
 
  
  
 
 
 
  
 
 
 
  
  
  
  
 
 
 
  
  
 
   
 
  
  
  
 
            
 

package com.mybatis.test;
import java.io.InputStream;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import lombok.Data;
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.Before;
import org.junit.Test;
import com.mybatis.dao.mapper.OrdersMapper;
import com.mybatis.dao.mapper.PersonMapper;
import com.mybatis.domain.Orders;
import com.mybatis.domain.Person;
public class TestStudentMapper {
 SqlSessionFactory sessionFactory = null;
 // 这方法之前
 @Before
 public void setup() throws Exception {
 String resource = "mybatis.xml";
 // 这个是加载配置文件
 InputStream inputStream = Resources.getResourceAsStream(resource);
 // 得到会话工厂
 sessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
 }
 //查询一对多 根据这个person里面的id号就能查询出这个用户有多少个订单记录
// @Test
 public void testSelectPersonById(){
 SqlSession sq = sessionFactory.openSession();
 // 得到dao层的实现类
 PersonMapper u = sq.getMapper(PersonMapper.class);
 Person person = u.selectPersonById("2");
 System.out.println(person);
 }
 //多对一 根据多对一id进行查询
// @Test//多对一关联查询 
   public void testSelectOrderById(){ 
   SqlSession sq = sessionFactory.openSession();
  // 得到dao层的实现类
   OrdersMapper u = sq.getMapper(OrdersMapper.class);
  Orders od = u.selectOrderById( "2");
  System.out.println(od.getPerson().getPersonname());
  System.out.println(od.getPerson().getPersonaddress());
   } 
  @Test//多对一关联查询 
   public void testSelectOrderNumber(){ 
   SqlSession sq = sessionFactory.openSession();
  // 得到dao层的实现类
   OrdersMapper u = sq.getMapper(OrdersMapper.class);
  Orders od = u.selectOrderNumber("001");
  System.out.println(od.getPerson().getPersonname());
  System.out.println(od.getPerson().getPersonaddress());
   } 
}