Hibernate框架中数据库多对多的演示

先是两个实体类的创建，这里我简单用物品类和订单类进行演示

package com.qiu.many_to_many;  //此处自己的工程包可以忽略import java.util.Set;/** * @author 邱 * @2017年9月20日 多对多 备注：物品类 */public class Goods {private long id;private String type; //商品类型private String name;private double price;private Set<Order> set;public long getId() {return id;}public void setId(long id) {this.id = id;}public String getType() {return type;}public void setType(String type) {this.type = type;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public Set<Order> getSet() {return set;}public void setSet(Set<Order> set) {this.set = set;}}

订单的实体类

package com.qiu.many_to_many;import java.util.Set;/** * @author 邱 * @2017年9月20日 * 备注： 订单类   多对多 */public class Order {private long id;//订单编号private double money;private String address;private Set<Goods> set;public long getId() {return id;}public void setId(long id) {this.id = id;}public double getMoney() {return money;}public void setMoney(double money) {this.money = money;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}public Set<Goods> getSet() {return set;}public void setSet(Set<Goods> set) {this.set = set;}}

实体类比较简单，大致看一下即可，主要是配置文件的编写

物品类的配置文件

<?xml version="1.0" encoding="UTF-8"?><!--  -->  <!--约束文件--><!DOCTYPE hibernate-mapping PUBLIC"-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><!-- 多对多外键 --><hibernate-mapping package="com.qiu.many_to_many"><class name="Goods" table="tb_goods"> <id name="id"> <generator class="native"></generator> </id> <property name="name" length="20"/><property name="type" length="10"/><property name="price" /><set name="set" table="tb_orderitem"><key column="gid"></key><many-to-many class="Order" column="oid"></many-to-many></set></class></hibernate-mapping>

订单的配置文件

<?xml version="1.0" encoding="UTF-8"?><!--  -->  <!--约束文件--><!DOCTYPE hibernate-mapping PUBLIC"-//Hibernate/Hibernate Mapping DTD 3.0//EN""http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"><!-- 一对一外键 --><hibernate-mapping package="com.qiu.many_to_many"><class name="Order" table="tb_order"> <id name="id"> <generator class="native"></generator> </id> <property name="money" /><property name="address" length="50"/><!--多对多  --><!--集合类型的属性name:属性名table：关系表的表名 --><set name="set" table="tb_orderitem"><!--当前的类在中间表的外键的名称  --><key column="oid"></key><!--集合的泛型的类型，标记与谁是多对多，并且指示中间表中的外键名称  --><many-to-many class="Goods" column="gid"></many-to-many></set></class></hibernate-mapping>

全局配置文件把 四本一言搞清楚一般不会错，记得把各个类的映射配置文件路径加上

<?xml version="1.0" encoding="UTF-8"?><!--约束文件 --><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><!-- 全局配置 --><hibernate-configuration><!--Session工厂的设置，其实就是连接设置 --><session-factory><!--四本一言四大基本标签：驱动、url、用户名、密码一言：方言，标记是哪一种数据库 --><!--1、数据库驱动类名全称 --><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><!--2、数据库的路径  --><property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate_1710_moretable?characterEncoding=UTF-8</property><!--3、数据库用户名  --><property name="hibernate.connection.username">root</property><!--4、密码  --><property name="hibernate.connection.password">123456</property><!--5、方言，一定要和数据库版本一致  --><property name="hibernate.dialect">org.hibernate.dialect.MySQL57Dialect</property><!--建表语句的执行：create\update  --><property name="hibernate.hbm2ddl.auto">update</property><!--显示自动生成的sql语句  --><property name="hibernate.show_sql">true</property><!--格式化sql语句  --><property name="hibernate.format_sql">true</property><!--启用安全Session，就是可以调用getCurrentSession  --><property name="hibernate.current_session_context_class">thread</property>

                <!--多对多外键映射  --><mapping resource="com/qiu/many_to_many/Goods.hbm.xml" /><mapping resource="com/qiu/many_to_many/Order.hbm.xml" /></session-factory></hibernate-configuration>

下面进行一些简单的演示

package com.qiu.many_to_many;import java.util.HashSet;import java.util.Set;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.After;import org.junit.Before;import org.junit.Test;import com.qiu.utils.HibernateUtils;/** * @author 邱 * @2017年9月20日  * 备注：多对多的演示 */public class MyTest {private Session session;private Transaction tran;// 每次测试方法执行之前调用@Beforepublic void bef() {session = HibernateUtils.openSession();tran = session.beginTransaction();}// 每次测试方法结束后调用@Afterpublic void aft() {tran.commit();session.close();}//多对多  新增：@Testpublic void test1(){Goods goods = new Goods();goods.setName("月饼");goods.setPrice(9.9);goods.setType("糕点");Order order = new Order();order.setMoney(9.9);order.setAddress("xxxxxxxxxxx");//这里只需要添加一次即可，否则重复添加Set<Goods> set2 = new HashSet<>();set2.add(goods);order.setSet(set2);System.out.println("新增："+ session.save(order));System.out.println("新增："+ session.save(goods));}//多对多查询@Testpublic void test2(){Order order2 = session.get(Order.class, 1l);System.out.println(order2.getAddress());for(Goods g : order2.getSet()){System.out.println(g.getName()+" "+g.getType());}Goods goods=session.get(Goods.class, 1l);System.out.println(goods.getName()+" "+goods.getPrice()+"----->");for(Order o : goods.getSet()){System.out.println(o.getAddress()+" "+o.getMoney());}}}