Hibernate 多对多关系
Hibernate 多对多关系
环境
java 12.0.1
Apache Maven 3.6.3
MySQL Server version: 5.7.18-20170830-log 20170531
hibernate-core-5.4.27.Final.jar
mysql-connector-java-8.0.21.jar
IntelliJ IDEA 2020.2.3 (Ultimate Edition)
Maven配置文件
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0modelVersion>
<groupId>com.demo.many-to-many-hibernategroupId>
<artifactId>ManyToManyHibernateartifactId>
<version>1.0-SNAPSHOTversion>
<dependencies>
<dependency>
<groupId>junitgroupId>
<artifactId>junitartifactId>
<version>4.12version>
<scope>testscope>
dependency>
<dependency>
<groupId>org.hibernategroupId>
<artifactId>hibernate-agroalartifactId>
<version>5.4.27.Finalversion>
<type>pomtype>
dependency>
<dependency>
<groupId>mysqlgroupId>
<artifactId>mysql-connector-javaartifactId>
<version>8.0.21version>
dependency>
<dependency>
<groupId>log4jgroupId>
<artifactId>log4jartifactId>
<version>1.2.17version>
dependency>
dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.pluginsgroupId>
<artifactId>maven-compiler-pluginartifactId>
<configuration>
<source>12source>
<target>12target>
configuration>
plugin>
plugins>
<resources>
<resource>
<directory>src/main/javadirectory>
<includes>
<include>**/*.hbm.xmlinclude>
includes>
resource>
resources>
build>
project>
Hibernate核心配置文件
src/main/resources/hibernate.cfg.xml
数据库参数
- [hostname] : 主机名（本地为
localhost） - [port] : 端口号（默认端口号为
3306） - [database] : 数据库名
- [username] : 用户名
- [password] : 密码
配置文件
<hibernate-configuration>
<session-factory>
<property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialectproperty>
<property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driverproperty>
<property name="hibernate.connection.url">jdbc:mysql://[hostname]:[port]/[database]property>
<property name="hibernate.connection.username">[username]property>
<property name="hibernate.connection.password">[password]property>
<property name="hibernate.show_sql">trueproperty>
<property name="hibernate.hbm2ddl.auto">updateproperty>
<mapping resource="com/demo/hibernate/many2many/User.hbm.xml"/>
<mapping resource="com/demo/hibernate/many2many/Commodity.hbm.xml"/>
session-factory>
hibernate-configuration>
映射文件
参数
-
set
- key : 外键
- column : 外键名
- one-to-many :
- class : 被参照类的包名和类名
- key : 外键
-
name : 被参照类对应的Set对象
-
table : 联系表
-
cascade : 级联保存
-
many-to-one
- name : 参照表名
- class : 参照类的包名和类名
- column : 外键名
User类映射文件
src/main/java/com/demo/hibernate/many2many/User.hbm.xml
<hibernate-mapping package="com.demo.hibernate">
<class name="com.demo.hibernate.many2many.User" table="user" catalog="hibernate">
<id name="id" column="id">
<generator class="native" />
id>
<property name="username" column="username" length="128">property>
<property name="password" column="password" length="128">property>
<set name="commodities" table="`order`" cascade="save-update">
<key column="user_id">key>
<many-to-many class="com.demo.hibernate.many2many.Commodity" column="commodity_id">many-to-many>
set>
class>
hibernate-mapping>
Commodity类映射文件
src/main/java/com/demo/hibernate/many2many/Commodity.hbm.xml
<hibernate-mapping package="com.demo.hibernate">
<class name="com.demo.hibernate.many2many.Commodity" table="commodity" catalog="hibernate">
<id name="id" column="id">
<generator class="native" />
id>
<property name="price" column="price">property>
<property name="name" column="name" length="128">property>
<property name="description" column="description" length="256">property>
<set name="users" table="`order`">
<key column="commodity_id">key>
<many-to-many class="com.demo.hibernate.many2many.User" column="user_id">many-to-many>
set>
class>
hibernate-mapping>
Java代码
User类
src/main/java/com/demo/hibernate/many2many/Commodity.java
package com.demo.hibernate.many2many;
import java.util.HashSet;
import java.util.Set;
public class User {
private int id;
private String username;
private String password;
private Set<Commodity> commodities;
public User(String user, String password) {
this.username = user;
this.password = password;
commodities = new HashSet<Commodity>();
}
public User() {
}
public Set<Commodity> getCommodities() {
return commodities;
}
public void setCommodities(Set<Commodity> commodities) {
this.commodities = commodities;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
Commodity类
src/main/java/com/demo/hibernate/many2many/Commodity.java
package com.demo.hibernate.many2many;
import java.util.HashSet;
import java.util.Set;
public class Commodity {
private int id;
private double price;
private String name;
private String description;
private Set<User> users;
public Commodity() {
}
public Commodity(double price, String name, String description) {
this.price = price;
this.name = name;
this.description = description;
users = new HashSet<User>();
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Set<User> getUsers() {
return users;
}
public void setUsers(Set<User> users) {
this.users = users;
}
}
Hibernate类
src/main/java/com/demo/hibernate/many2many/Hibernate.java
package com.demo.hibernate.many2many;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
public class Hibernate {
private Configuration configuration;
private StandardServiceRegistry standardServiceRegistry;
private SessionFactory sessionFactory;
protected Session session;
protected Transaction transaction;
public Hibernate() {
try {
configuration = new Configuration();
configuration.configure("hibernate.cfg.xml");
standardServiceRegistry = new StandardServiceRegistryBuilder().configure().build();
sessionFactory = configuration.buildSessionFactory(standardServiceRegistry);
session = sessionFactory.openSession();
transaction = session.beginTransaction();
} catch (Exception e) {
e.printStackTrace();
}
}
public void commit() {
transaction.commit();
}
public void insert(User user) {
session.save(user);
}
public static void main(String[] args) {
Hibernate hibernate = new Hibernate();
User user1 = new User("Tony", "123456");
User user2 = new User("Tom", "123456");
Commodity commodity1 = new Commodity(32.0, "Coke", "Coca Cola 24 cans");
Commodity commodity2 = new Commodity(64.0, "Milk", "Milk 24 bottles");
Commodity commodity3 = new Commodity(128.0, "T-shirt", "T-shirt");
Commodity commodity4 = new Commodity(256.0, "Coat", "Coat");
user1.getCommodities().add(commodity1);
user1.getCommodities().add(commodity2);
user1.getCommodities().add(commodity3);
user1.getCommodities().add(commodity4);
user2.getCommodities().add(commodity1);
hibernate.insert(user1);
hibernate.insert(user2);
hibernate.commit();
}
}
测试结果
select user.id user_id, username, commodity.id commodity_id, name commodity_name, price, description commodity_description from user left join `order` on `order`.user_id = user.id left join commodity on `order`.commodity_id = commodity.id;
最后
- 由于博主水平有限，不免有疏漏之处，欢迎读者随时批评指正，以免造成不必要的误解！