Mybatis多对多操作-建立新的关系和删除新关系
目录
数据库
1、product_表
插入数据：
建表sql文：
use mybatistest1;
create table product_(
id int NOT NULL AUTO_INCREMENT,
name varchar(30) DEFAULT NULL,
price float DEFAULT 0,
cid int ,
PRIMARY KEY (id)
)AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
3、创建order_表
建表sql：
create table order_(
id int(11) NOT NULL AUTO_INCREMENT,
code VARCHAR(32) DEFAULT NULL,
PRIMARY KEY(id)
)ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
4、order_item表
建表sql：
CREATE table order_item_(
id int(11) not null auto_increment,
oid int,
pid int,
number int,
PRIMARY KEY(id)
)AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
代码
pojo实体类Order.java
package com.mybatis.pojo;
import java.util.List;
//系统订单由无数个，但是有些有没有关联到特定的产品
public class Order {
private int id;
private String code;
List<OrderItem> orderItems;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public List<OrderItem> getOrderItems() {
return orderItems;
}
public void setOrderItems(List<OrderItem> orderItems) {
this.orderItems = orderItems;
}
}
pojo实体类OrderItem.java
package com.mybatis.pojo;
//表示系统内其中一对关联，该关联表示多个订单关联到多个产品，需要查找的特定订单和产品
public class OrderItem {
private int id;
private int number;
private Order order;
private Product product;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getNumber() {
return number;
}
public void setNumber(int number) {
this.number = number;
}
public Order getOrder() {
return order;
}
public void setOrder(Order order) {
this.order = order;
}
public Product getProduct() {
return product;
}
public void setProduct(Product product) {
this.product = product;
}
}
pojo实体类Product.java
package com.mybatis.pojo;
//系统内由很多产品，但是不一定是全部都关联到需要查找的特定的订单
public class Product {
private int id;
private String name;
private float price;
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 float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
@Override
public String toString() {
return "Product [id=" + id + ", name=" + name + ", price=" + price + "]";
}
}
Order.xml
<mapper namespace="com.mybatis.pojo">
<resultMap type="Order" id="orderBean">
<id column="oid" property="id"/>
<result column="ocode" property="code"/>
<collection property="orderItems" ofType="OrderItem">
<id column="oiid" property="id"/>
<result column="oinumber" property="number"/>
<association property="product" javaType="Product">
<id column="pid" property="id"/>
<result column="pname" property="name"/>
<result column="pprice" property="price"/>
association>
collection>
resultMap>
<select id="listOrder" resultMap="orderBean">
select o.*,p.*,o.id 'oid',o.code 'ocode',p.id 'pid',p.name 'pname',p.price 'pprice',oi.id 'oiid',oi.oid 'oioid',oi.pid 'oipid',oi.number 'oinumber'
from order_ o
left join order_item_ oi
on o.id=oi.oid
left join product_ p
on oi.pid=p.id
select>
<select id="getOrder" resultMap="orderBean">
select o.*,p.*,o.id 'oid',o.code 'ocode',p.id 'pid',p.name 'pname',p.price 'pprice',oi.id 'oiid',oi.oid 'oioid',oi.pid 'oipid',oi.number 'oinumber'
from order_ o
left join order_item_ oi
on o.id=oi.oid
left join product_ p
on oi.pid=p.id
where o.id=#{id}
select>
mapper>
OrderItem.xml
<mapper namespace="com.mybatis.pojo">
<insert id="addOrderItem" parameterType="OrderItem">
insert into order_item_
values(null,#{order.id},#{product.id},#{number})
insert>
<insert id="deleteOrderItem" parameterType="OrderItem">
delete from order_item_
where oid=#{order.id} and pid=#{product.id}
insert>
mapper>
Product.xml
<mapper namespace="com.mybatis.pojo">
<select id="getProduct" resultType="Product">
select p.*
from product_ p
where p.id=#{id}
select>
mapper>
全局配置文件
<configuration>
<typeAliases>
<package name="com.mybatis.pojo"/>
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/mybatistest1?characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="zhao8888"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/mybatis/pojo/Order.xml"/>
<mapper resource="com/mybatis/pojo/OrderItem.xml"/>
<mapper resource="com/mybatis/pojo/Product.xml"/>
mappers>
configuration>
1、测试主类-建立新关系testMybatis.java
package com.mybatis;
import java.awt.event.ItemEvent;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 com.mybatis.pojo.*;
public class testMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml"; //获取全局配置信息
InputStream inputStream = Resources.getResourceAsStream(resource); //全局配置信息装入输入流
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //建立sql会话工厂，将输入流装入
SqlSession session=sqlSessionFactory.openSession(); //开启一个会话
addOrderItem(session);
listOrder(session);
session.commit(); //更新到数据库
session.close();
}
private static void addOrderItem(SqlSession session) {
Order o1=session.selectOne("getOrder",1); //从数据库里面查到id=1的字段内容，映射到Order对象中；Order对象包括属性：id，code，OrderItem集合；OrderItem集合包括属性：id，oid，pid，number，product；Product对象包括属性：id，name，price
Product p6=session.selectOne("getProduct",6); //从数据库里面找到id=6的字段内容，映射到Product对象中，该对象包括属性：id，name，price
OrderItem oi=new OrderItem();
oi.setOrder(o1);
oi.setProduct(p6);
oi.setNumber(300);
//可以看作session为mybatis的虚拟数据库，order_item_表插入id，oid，pid，number
//此处创建了一个新的OrderItem对象，映射出新的订单和产品关系（OrderItem对象）
session.insert("addOrderItem", oi);
}
private static void listOrder(SqlSession session) {
List<Order> os=session.selectList("listOrder");
for(Order o:os) {
System.out.println(o.getCode());
List<OrderItem> ois=o.getOrderItems();
for(OrderItem oi:ois) {
System.out.format("\t%s\t%f\t%d%n",oi.getProduct().getName(),oi.getProduct().getPrice(),oi.getNumber());
}
}
}
}
2、测试主类-删除新关系
package com.mybatis;
import java.awt.event.ItemEvent;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 com.mybatis.pojo.*;
public class testMybatis {
public static void main(String[] args) throws IOException {
String resource = "mybatis-config.xml"; //获取全局配置信息
InputStream inputStream = Resources.getResourceAsStream(resource); //全局配置信息装入输入流
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); //建立sql会话工厂，将输入流装入
SqlSession session=sqlSessionFactory.openSession(); //开启一个会话
//addOrderItem(session);
deleteOrderItem(session);
listOrder(session);
session.commit(); //更新到数据库
session.close();
}
private static void addOrderItem(SqlSession session) {
Order o1=session.selectOne("getOrder",1);
Product p6=session.selectOne("getProduct",6);
OrderItem oi=new OrderItem();
oi.setOrder(o1);
oi.setProduct(p6);
oi.setNumber(300);
//可以看作session为mybatis的虚拟数据库，order_item_表插入id，oid，pid，number
session.insert("addOrderItem", oi);
}
private static void deleteOrderItem(SqlSession session) {
Order o1=session.selectOne("getOrder", 1);
Product p6=session.selectOne("getProduct", 6);
OrderItem oi=new OrderItem();
oi.setOrder(o1);
oi.setProduct(p6);
oi.setNumber(300);
session.delete("deleteOrderItem",oi);
}
private static void listOrder(SqlSession session) {
List<Order> os=session.selectList("listOrder");
for(Order o:os) {
System.out.println(o.getCode());
List<OrderItem> ois=o.getOrderItems();
for(OrderItem oi:ois) {
System.out.format("\t%s\t%f\t%d%n",oi.getProduct().getName(),oi.getProduct().getPrice(),oi.getNumber());
}
}
}
}
结果
建立一个关系
删除一个关系：
总结
1、session.selectList()返回的是类的对象：数据库处理由mybatis通过自己定义的sql语句进行处理，返回到mybatis自动映射的类或自己定义的映射关系（一对多或多对一是由自己定义），可以认为一个session就是mybatis的数据库
2、无论建立关系还是删除关系都是通过对OrderItem对象操作来完成