Hibernate学习笔记三（之）——关联关系一对多映射

本是古典何须时尚 2022-05-17 12:27 222阅读 0赞

项目总览图：

![70][]

Class.java

package com.java1234.model;
    
    public class Class {
    	private long id;
    	private String name;
    	private Class c;
    
    	//...省略get&setter
    }

Student.java

public class Student {
    	
    	private long id;
    	private String name;
    	private Class c;
            //...省略get&set方法
    }

Class.hbm.xml

<?xml version="1.0"?>
    <!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.java1234.model">
    	<class name="Class" table="t_class">
    		
    		<id name="id" column="classId">
    			<generator class="native"></generator>
    		</id>
    		<property name="name" column="className"></property>
    	</class>
    </hibernate-mapping>

Student.hbm.xml  **主要配置项：<many-to-one name="c" column="classId" class="com.java1234.model.Class"></many-to-one>**

在<many-to-one>这端，cascade 默认是”none”，假如我们希望在持久化多的一端的时候，自动级 联保存和更新一的一端，我们可以把 **cascade 设置成”save-update”；**

<?xml version="1.0"?>
    <!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.java1234.model">
    	<class name="Student" table="t_student">
    		
    		<id name="id" column="stuId">
    			<generator class="native"></generator>
    		</id>
    		<property name="name" column="stuName"></property>
    		<many-to-one name="c" column="classId" class="com.java1234.model.Class"></many-to-one>
    	</class>
    </hibernate-mapping>

HibernateUtil.java

package com.java1234.util;
    
    import org.hibernate.SessionFactory;
    import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
    import org.hibernate.cfg.Configuration;
    import org.hibernate.service.ServiceRegistry;
    
    public class HibernateUtil {
    	private static final SessionFactory sessionFactory = buildSessionFactory();
    	
    	private static SessionFactory buildSessionFactory() {
    		Configuration configuration = new Configuration().configure();
    		ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();//实例化服务登记
    		SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);//获取Session工厂
    		return sessionFactory;
    	}
    	
    	public static SessionFactory getSessionFactory() {
    		return sessionFactory;
    	}
    }

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
    <!DOCTYPE hibernate-configuration PUBLIC
            "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
            "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">
    
    <hibernate-configuration>
    
        <session-factory>
    
            
            <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
            <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>
            <property name="connection.username">root</property>
            <property name="connection.password">root</property>
    
           
            
            <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
    	
            
            <property name="show_sql">true</property>
    
            
            <property name="hbm2ddl.auto">update</property>
            
      		<mapping resource="com/java1234/model/Student.hbm.xml"/>
      		<mapping resource="com/java1234/model/Class.hbm.xml"/>
        </session-factory>
    
    </hibernate-configuration>

test方法：

StudentTest.java

package com.java1234.service;
    
    import org.hibernate.Session;
    import org.hibernate.SessionFactory;
    
    import com.java1234.model.Class;
    import com.java1234.model.Student;
    import com.java1234.util.HibernateUtil;
    
    public class StudentTest {
    	
    	public static void main(String[] args) {
    		
    		SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
    		Session session = sessionFactory.openSession();//生成一个session会话
    		session.beginTransaction();//开启事务
    		
    		Class c = new Class();
    		c.setName("08计本");
    		session.save(c);
    		
    		Student s1 = new Student();
    		s1.setName("张三");
    		s1.setC(c);
    		
    		Student s2 = new Student();
    		s2.setName("李四");
    		s2.setC(c);
    		
    		session.save(s1);
    		session.save(s2);
    		
    		session.getTransaction().commit();//提交事务
    		session.close();//关闭session
    		
    	}
    	
    }

数据库结果：

数据库架构图：

![70 1][]

![70 2][]

![70 3][]

[70]: /images/20220517/ea1a3e8aba7742df80ee058233f6c3e3.png
[70 1]: /images/20220517/2d7243c519524f6985adadb44750423e.png
[70 2]: /images/20220517/4ed234d430504911805443a17780619c.png
[70 3]: /images/20220517/68ec07a02a984790afb5bb5391d8999d.png