Hibernateday05继承关系joined-subclass映射策略-白红宇

Hibernateday05继承关系joined-subclass映射策略

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发布时间：2019-05-26

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2.joined-subclass映射策略

特点：父表的数据由父表保存，子表的数据由父表和子表共同保存。子类和父类共有的

属性保存在父表当中，子类扩展的属性保存在子表当中。采取该策略不需要辨别列。要为子表提供一个列【主键】映射父表的主键

表：

create table g_product( --父表--

p_id integer primary key,

p_name varchar2(30),

p_price number(4,2)

)

create table g_book( --子表--

c_id integer primary key references g_product(p_id),--与父表关联--

c_author varchar2(40)

)

映射文件

<joined-subclass name="Book" table="g_book" >

</joined-subclass>

1.O提供对象属性实体类Product.java 和 Book.java

package com.jsu.hb.pojo;public class Product {	private Integer id;	private String name;	private Double price;	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 Double getPrice() {		return price;	}	public void setPrice(Double price) {		this.price = price;	}	}

Book.java

package com.jsu.hb.pojo;public class Book extends Product {	private String author;	public String getAuthor() {		return author;	}	public void setAuthor(String author) {		this.author = author;	}	}

2.R建表

create table g_product(	p_id integer primary key,	p_name varchar2(30),	p_price number(6,2))create table g_book(	c_id integer primary key references g_product(p_id),	c_author varchar2(40))

3.提供映射文件joined.hbm.xml

4.在hibernate.cfg.xml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.提供工具类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.提供测试类TestJoined.java

package com.jsu.hb.test;import org.hibernate.Session;import org.hibernate.Transaction;import org.junit.Test;import com.jsu.hb.pojo.Book;import com.jsu.hb.pojo.Product;import com.jsu.hb.util.HibernateUtil;public class TestJoined {	@Test	public void save(){		Product p = new Product();		p.setName("小米");		p.setPrice(1999.0);				Book b = new Book();		b.setName("围城");		b.setPrice(38.5);		b.setAuthor("沈从文");				Session session = HibernateUtil.getCurrentSession();		Transaction tx = session.getTransaction();		tx.begin();		session.save(p);//保存产品		//session.save(b);//保存图书		tx.commit();	}}

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