Hibernate学习笔记第二篇 关联关系映射 many –to –one

 many –to –one

假设2个对象,分别是Person and Address .

1个Address中含有多个Person

分别建立类

package cn.itcase.hibernate.domain;

public class Address {
 private int id;
 private String street;
 
 public int getId() {
        return id;
    }
public void setId(int id) {
        this.id = id;
    }

public String getStreet() {
    return street;
}
public void setStreet(String street) {
    this.street = street;
}

}


package cn.itcase.hibernate.domain;

public class Person {
 private int id;
 private String name;
 private Address address;
 
public Address getAddress() {
    return address;
}
public void setAddress(Address address) {
    this.address = address;
}
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;
}
}

相对应的配置文件为

<?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="cn.itcase.hibernate.domain">
	<class name="Address" table="address">
		<id name="id" >
			<generator class="native" />
		</id>
		<property name="street"></property>
	
	
	</class>
</hibernate-mapping>

<?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="cn.itcase.hibernate.domain">
	<class name="Person" table="person">
		<id name="id" >
			<generator class="native" />
		</id>
		<property name="name" />
	   <!--留意这里 name的名称必须和address类中的private Address addr;对象名称一致 
	     列名可任意命名,最好是具有相对意义
	    -->	
		<many-to-one name="address" column="addressId"/>
	</class>
</hibernate-mapping>

//测试多对一例子

package cn.itcast.hibernate;

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

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;

import cn.itcase.hibernate.domain.Address;
import cn.itcase.hibernate.domain.Person;

public class many2one2 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Person depart=add();
		Person emp=query(1);
		//System.out.println(emp.getDepart().getName());
		//queryDepart(3);
		//System.out.println(addrquery(1).getPer().getName());
	}
	
	

	static Address addrquery(int id){
		Session s=null;
		Transaction tx=null;
		try{
			s=HibernateUtil.getSession();
			tx=s.beginTransaction();
			Address addr=(Address)s.get(Address.class, id);
			//System.out.print(emp.getDepart().getName());
			Hibernate.initialize(addr.getStreet());
			tx.commit();
			return addr;
		}finally{
			if(s!=null)
				s.close();
		}	
	}

	static Person query(int pid){
		Session s=null;
		Transaction tx=null;
		try{
			s=HibernateUtil.getSession();
			tx=s.beginTransaction();
			Person p=(Person)s.get(Person.class, pid);
			tx.commit();
			return p;
		}finally{
			if(s!=null)
				s.close();
		}		
	}

	static Person add(){
		Session s=null;
		Transaction tx=null;
		try{
			Address addr1=new Address();
			addr1.setStreet("add1");	

			Person p1=new Person();
			p1.setName("p1");

			Person p2=new Person();
			p2.setName("p2");

			p1.setAddress(addr1);
			p2.setAddress(addr1);

			s=HibernateUtil.getSession();
			tx=s.beginTransaction();

			s.save(addr1);
			s.save(p1);
			s.save(p2);
			tx.commit();
			return p1;
		}finally{
			if(s!=null)
				s.close();
		}	
	}

}