Hibernate 多对一单向关联的一个例子（备忘用）

这是一个多对一单向关联的一个例子，目的是为了总结一下Hibernate的基础知识。

生成 Classes  和student类

 

package com.test.hibernate;

import java.util.Set;

public class Classes {
	
	private int id;
	
	private String name;
	
	private Set students; 
	
	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 Set getStudents() {
		return students;
	}

	public void setStudents(Set students) {
		this.students = students;
	}
	
}

 

 

package com.test.hibernate;

public class Student {
	
	private int id;
	
	private String name;

	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;
	}
}

 

 

生成Classes.hbm.xml和Student.hbm.xml文件。

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.test.hibernate">
	<class name="Classes" table="t_classes">
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name"/>
		<set name="students">
			<key column="classesid"/>
			<one-to-many class="Student"/>
		</set>
	</class>
</hibernate-mapping>

 XML配置最主要的为：

<set name="students">
   <key column="classesid"/>
   <one-to-many class="Student"/>
</set>
将Student对应的表添加一个 classesid属性。

package com.test.hibernate;

public class Student {
	
	private int id;
	
	private String name;

	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;
	}
}

 

生成hibernate.cfg.xml文件

<!DOCTYPE hibernate-configuration PUBLIC
	"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory>
		<property name="hibernate.connection.url">jdbc:mysql://localhost/mytest</property>
		<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="hibernate.connection.username">root</property>
		<property name="hibernate.connection.password">123456</property>
		<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="hbm2ddl.auto">create</property>
		<property name="hibernate.show_sql">true</property>
		
		<mapping resource="com/test/hibernate/Student.hbm.xml"/>
		<mapping resource="com/test/hibernate/Classes.hbm.xml"/>
	</session-factory>
</hibernate-configuration>

 写JAVA代码进行OR转换

为了避免重复写代码，可以把一些初始化的东西写到一个类中！其它类调用这个类的方法和属性。

HibernateUtils.java如下：

package com.test.hibernate;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateUtils {
private static SessionFactory factory;
	
	static {
		try {
			Configuration cfg = new Configuration().configure();
			factory = cfg.buildSessionFactory();
		}catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public static SessionFactory getSessionFactory() {
		return factory;
	}
	
	public static Session getSession() {
		return factory.openSession();
	}
	
	public static void closeSession(Session session) {
		if (session != null) {
			if (session.isOpen()) {
				session.close();
			}
		}
	}

}

 

生成主类 TestOne2Many.java

package com.test;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;

import com.test.hibernate.Classes;
import com.test.hibernate.HibernateUtils;
import com.test.hibernate.Student;

public class TestOne2Many {

	public static void main(String[] args) {

		testSave1();
		
	}
	public static void testSave1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			
			Student student1 = new Student();
			student1.setName("10");
			session.save(student1);
			
			Student student2 = new Student();
			student2.setName("祖儿");
			session.save(student2);
			
			Set students = new HashSet();
			students.add(student1);
			students.add(student2);
			
			Classes classes = new Classes();
			classes.setName("尚学堂");
			classes.setStudents(students);
			
			session.save(classes);
			
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}	

}