Hibernate 一對多關係
阿新 • • 發佈：2021-02-04
技術標籤：JavaHibernatehibernatemysqljava
Hibernate 一對多關係
環境
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配置檔案
<?xml version="1.0" encoding="UTF-8"?> Hibernate核心配置檔案
src/main/resources/hibernate.cfg.xml
資料庫引數
- [hostname] : 主機名（本地為
localhost） - [port] : 埠號（預設埠號為
3306） - [database] : 資料庫名
- [username] : 使用者名稱
- [password] : 密碼
配置檔案
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration SYSTEM
"http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- dialect configuration -->
<property name="hibernate.dialect">org.hibernate.dialect.MySQL8Dialect</property>
<property name="hibernate.connection.driver_class">com.mysql.cj.jdbc.Driver</property>
<!-- database configuration -->
<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>
<!-- hibernate configuration-->
<property name="hibernate.show_sql">true</property>
<!-- update: create if table not exist, else update-->
<property name="hibernate.hbm2ddl.auto">update</property>
<!-- mapping resource -->
<mapping resource="com/demo/hibernate/one2many/User.hbm.xml"/>
<mapping resource="com/demo/hibernate/one2many/Order.hbm.xml"/>
</session-factory>
</hibernate-configuration>
對映檔案
引數
-
set
- key : 外來鍵
- column : 外來鍵名
- one-to-many :
- class : 被參照類的包名和類名
- key : 外來鍵
-
name : 被參照類對應的Set物件
-
cascade : 級聯儲存
-
many-to-one
- name : 參照表名
- class : 參照類的包名和類名
- column : 外來鍵名
User類對映檔案
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.demo.hibernate">
<class name="com.demo.hibernate.one2many.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="orders" cascade="save-update">
<key column="user_id"></key>
<one-to-many class="com.demo.hibernate.one2many.Order"/>
</set>
</class>
</hibernate-mapping>
Order類對映檔案
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.demo.hibernate">
<class name="com.demo.hibernate.one2many.Order" table="order" catalog="hibernate">
<id name="id" column="id">
<generator class="native" />
</id>
<property name="price" column="price"></property>
<property name="timestamp" column="timestamp" length="128"></property>
<many-to-one name="user" class="com.demo.hibernate.one2many.User" column="user_id"></many-to-one>
</class>
</hibernate-mapping>
Java程式碼
User類
src/main/java/com/demo/hibernate/one2many/User.java
package com.demo.hibernate.one2many;
import java.util.HashSet;
import java.util.Set;
public class User {
private int id;
private String username;
private String password;
private Set<Order> orders;
public User(String user, String password) {
this.username = user;
this.password = password;
orders = new HashSet<Order>();
}
public User() {
orders = new HashSet<Order>();
}
public Set<Order> getOrders() {
return orders;
}
public void setOrders(Set<Order> orders) {
this.orders = orders;
}
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;
}
}
Order類
src/main/java/com/demo/hibernate/one2many/Order.java
package com.demo.hibernate.one2many;
public class Order {
private int id;
private double price;
private String timestamp;
private User user;
public Order() {
}
public Order(double price, String timestamp) {
this.price = price;
this.timestamp = timestamp;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = 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 getTimestamp() {
return timestamp;
}
public void setTimestamp(String timestamp) {
this.timestamp = timestamp;
}
}
Hibernate類
src/main/java/com/demo/hibernate/one2many/Hibernate.java
package com.demo.hibernate.one2many;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.SessionFactory;
import java.util.*;
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 insert(User user) {
session.save(user);
transaction.commit();
}
public static void main(String[] args) {
Hibernate hibernate = new Hibernate();
Date date = new Date();
User user = new User("Tony", "123456");
Set<Order> orders = new HashSet<Order>();
orders.add(new Order(512.0, date.toString()));
orders.add(new Order(1024.0, date.toString()));
orders.add(new Order(2048.0, date.toString()));
orders.add(new Order(4096.0, date.toString()));
user.setOrders(orders);
hibernate.insert(user);
}
}
測試結果
select user.id user_id, user.username, `order`.id order_id, `order`.price, `order`.timestamp from user left join `order` on user.id = `order`.user_id;
最後
- 由於博主水平有限，不免有疏漏之處，歡迎讀者隨時批評指正，以免造成不必要的誤解！