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一对一：唯一外键：为外键加上唯一约束

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

 4.在hibernate.cfg.cml文件中对映射文件进行注册

   	
     		
     		
     
      true
     		
     		
     
      true
     		
     		
     
      oracle.jdbc.OracleDriver
     		
     
      jdbc:oracle:thin:@127.0.0.1:1521:oracle
     		
     
      scott
     		
     
      tiger
     		
     		
     
      org.hibernate.dialect.Oracle9iDialect
     		
     	
    
   

 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
   
     tl= new ThreadLocal
    
     ();	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();	}}

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