用hibernate实现java的类继承-每个类一个表

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在Hibernate中，有三种方式实现java中的继承，本文讲一个方法：每个类一张表。

java是面向对象的编程语言。继承是其中重要的概念。关系模型能实现“是一个”和“有一个"关系。Hibernate给我们提供了类继承的方法。

比如我们有下面的类：shape是基类，circle和rectangle继承了shape.我们将为这3个类生成3张表。

三个类：

三张表：

package org.arpit.javapostsforlearning;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.Inheritance;import javax.persistence.InheritanceType;import javax.persistence.Table;@Entity@Table(name="SHAPE")@Inheritance(strategy=InheritanceType.TABLE_PER_CLASS)public class Shape { @Id @GeneratedValue(strategy = GenerationType.TABLE) @Column(name="Shape_Id") int shapeId; @Column(name="Shape_Name") String shapeName;   public Shape() {   } public Shape(String shapeName) {  this.shapeName=shapeName; } //getters and setters }

为在hibernate中实现继承，要用@Inheritance.它为实现实体类的层次结构，它定义了继承策略。我们在此使用的是Table_Per_Class继承策略。

package org.arpit.javapostsforlearning;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Table;@Entity@Table(name="RECTANGLE")public class Rectangle extends Shape{ @Column(name="Rectangle_Length") int length; @Column(name="Rectangle_Breadth") int breadth; // getters and setters  public Rectangle() {   }  public Rectangle(String shapeName,int length,int breadth) {  super(shapeName);  this.length=length;  this.breadth=breadth; }  // getters and setters}

package org.arpit.javapostsforlearning;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Table;@Entity@Table(name="CIRCLE")public class Circle extends Shape{ @Column(name="Circle_Radius") int radius;  public Circle() {   } public Circle(String shapeName,int radius) {  super(shapeName);  this.radius=radius;   } // getters and setters}

package org.arpit.javapostsforlearning;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;import org.hibernate.service.ServiceRegistryBuilder;public class HibernateMain { public static void main(String[] args) {    Shape shape=new Shape("Sqaure");  Rectangle rectangle=new Rectangle("Rectangle", 10, 20);    Circle circle=new Circle("Circle", 4);      Configuration configuration=new Configuration();  configuration.configure();  ServiceRegistry sr= new ServiceRegistryBuilder().applySettings(configuration.getProperties()).buildServiceRegistry();  SessionFactory sf=configuration.buildSessionFactory(sr);  Session ss=sf.openSession();    ss.beginTransaction();  ss.save(shape);  ss.save(rectangle);  ss.save(circle);  ss.getTransaction().commit();  ss.close();   }}

原文：http://javapostsforlearning.blogspot.in/2013/02/hibernate-inheritancetable-per-concrete.html

源代码：http://pan.baidu.com/share/link?shareid=3213551302&uk=3878681452
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另见生成一张表：http://188029.net/hibernate/hib.html