Hibernateday02表的唯一外键

一对一：唯一外键：为外键加上唯一约束
    公司  Company      地址  Address
关系属性  Address            Coompany

 

1.唯一外键建表

create table g_company(
      t_id Integer primary key,
      t_name varchar2(30),
      t_regdate date
)

create table g_address(
       t_id Integer primary key,
       t_city varchar2(30),
       t_zip Integer,
       c_id integer references g_company(t_id)
)

 2.在com.jsu.hb.pojo包中创建实体类Company和Address

package com.jsu.hb.pojo;

import java.util.Date;

public class Company {
	private Integer id;
	private String name;
	private Date regdate;
	private Address address;
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Date getRegdate() {
		return regdate;
	}
	public void setRegdate(Date regdate) {
		this.regdate = regdate;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	
}

 在Address.java中

package com.jsu.hb.pojo;

public class Address {
	private Integer id;
	private String city;
	private String zip;
	private Company company;
	//提供工具方法，在内存中解除与Company的关系
	public void remove(Company city){
		this.company=null;
		city.setAddress(null);
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getZip() {
		return zip;
	}
	public void setZip(String zip) {
		this.zip = zip;
	}
	public Company getCompany() {
		return company;
	}
	public void setCompany(Company company) {
		this.company = company;
	}
	
}

 3.提供映射文件在o2ofk.hbm.xml文件中

<?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.jsu.hb.pojo">
	<class name="Company" table="g_company">
		<!-- id属性配置 -->
		<id name="id" column="t_id">
			<generator class="increment"></generator>
		</id>
		<!-- 普通属性配置 -->
		<property name="name" column="t_name"></property>
		<property name="regdate" column="t_regdate" type="java.util.Date"></property>
		<!-- 配置关系属性
			cascade="save-update":表示删除公司表时不级联删除地址表
			property-ref="c":Address通过关系属性Company的配置间接获得外键
		 -->
		 <one-to-one name="address" class="Address" cascade="save-update"></one-to-one>
	</class>
	<class name="Address" table="g_address">
		<id name="id" column="t_id">
			<generator class="increment"></generator>
		</id>
		<!-- 普通属性配置 -->
		<property name="city" column="t_city"></property>
		<property name="zip" column="t_zip"></property>
		<!-- 配置关系属性 :唯一外键
			因为Address有外键的存在，Address在本质上是多对一(many-to-one)Company，
			通过unique="true"：设置外键的唯一性约束
		-->
		<many-to-one name="company" class="Company" unique="true" column="c_id" cascade="save-update" ></many-to-one>
	</class>
</hibernate-mapping>

 4.在hibernate.cfg.cml文件中对映射文件进行注册

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

<hibernate-configuration>
	<session-factory> 
		<!-- show_sql:是否显示hibernate执行的SQL语句，默认为false -->
		<property name="show_sql">true</property>
		<!-- show_sql:是否显示hibernate执行格式化输出的SQL语句，默认为false -->
		<property name="format_sql">true</property>
		<!-- 配置与数据库连接的参数 -->
		<property name="connection.driver_class">oracle.jdbc.OracleDriver</property>
		<property name="connection.url">jdbc:oracle:thin:@127.0.0.1:1521:oracle</property>
		<property name="connection.username">scott</property>
		<property name="connection.password">tiger</property>
		<!-- 2.自身属性相关的配置
			dialect:方言
			hibernate根据dialect的配置进行特定数据性能方面的调优
		 -->
		<property name="dialect">org.hibernate.dialect.Oracle9iDialect</property>
		<mapping resource="com/jsu/hb/pojo/o2ofk.hbm.xml"></mapping>
	</session-factory>
</hibernate-configuration>

 5.在com.jsu.hb.util包中提供HibernateUtil.java

package com.jsu.hb.util;

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

public class HibernateUtil {
	private static SessionFactory sf;
	private static ThreadLocal<Session> tl= new ThreadLocal<Session>();
	static{
		try{
				Configuration cfg = new Configuration();
				cfg.configure();
				sf=cfg.buildSessionFactory();
		}catch(Exception e){
			e.printStackTrace();
		}
	}
	public static Session openSession(){
		return sf.openSession();
	}
	public static Session getCurrentSession(){
		Session session = tl.get();//先从储存的线程中查找
		if(session==null){
			session=openSession();
			tl.set(session);
			return session;
		}
		return session;
	}
}

 6.在com.jsu.hb.test包中提供测试类TestOnetoOneFK.java

 

package com.jsu.hb.test;

import java.util.Date;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.jsu.hb.pojo.Address;
import com.jsu.hb.pojo.Company;
import com.jsu.hb.util.HibernateUtil;

public class TestOnetoOneFK {
	@Test
	public void save(){
		Company c = new Company();
		c.setName("51Gowoo");
		c.setRegdate(new Date());
		Address a = new Address();
		a.setCity("长沙");
		a.setZip("410012");
		//在内存中设定他们之间的关系
	     c.setAddress(a);
	     a.setCompany(c);
		//创建对象
		Session session =HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		session.save(c);
		tx.commit();
	}
	//查询
	@Test
	public void query(){
		Session session =HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		Company c = (Company)session.get(Company.class, 2);
		System.out.println(c.getName()+" : "+c.getRegdate());
		System.out.println(c.getAddress().getCity()+" : "+c.getAddress().getZip());
		tx.commit();
	}
	
	//删除
	@Test
	public void del(){
		Session session =HibernateUtil.getCurrentSession();
		Transaction tx = session.getTransaction();
		tx.begin();
		Company c = (Company)session.get(Company.class, 2);
		//解除对象在内存中的关系
		c.getAddress().remove(c);
		session.delete(c);
		/*
		 * 失败：虽然设置了级联为save-update,hibernate不是直接操作数据库，直接操作对象（内存当中）
		 * 通过session.get(Company.class, 1);获得了Company对象，根据传递性持久化会把Address
		 * 一起查询，实际操作了两个对象，而且这两个对象在内存中依旧保持关系，传递性持久化会将关联的 对象一起删除，所以报异常 deleted
		 * object would be re-saved by cascade 解决方式：要在删除前 解除对象在内存中的关系
		 * 1.为Address提供工具方法，解除内存中的关系
		 * 
		 */
		tx.commit();
	}

}