BaseEntity实体的继承：@MappedSuperclass

在创建实体时，经常有重复的id和时间的属性要创建，所以想弄一个父类，然后所有实体继承，但是碰到了问题，就用到了@MappedSuperclass，它的的用法
用在实体的继承过程中的父类上；
如：
IdEntity.java

package com.zpf.test.Entity;

import java.io.Serializable;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;

/**
 * 基础实体类
 * 
 * @author zpf
 * 
 */
@MappedSuperclass
public class IdEntity implements Serializable {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	@Id
	@GeneratedValue(strategy = GenerationType.AUTO)
	private long id;

	@Column(updatable = false)
	private Date createDate;
	private Date modifyDate;

	public long getId() {
		return id;
	}

	public void setId(long id) {
		this.id = id;
	}

	public Date getCreateDate() {
		return createDate;
	}

	public void setCreateDate(Date createDate) {
		this.createDate = createDate;
	}

	public Date getModifyDate() {
		return modifyDate;
	}

	public void setModifyDate(Date modifyDate) {
		this.modifyDate = modifyDate;
	}

}

package com.zpf.test.Entity;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.Table;

/**
 * 用户实体
 * @author zpf
 *
 */
@Entity
@Table(name="tb_user")
public class User extends IdEntity implements Serializable{

	private static final long serialVersionUID = 1L;

	private String name;

	private String sex;

	private int age;

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getSex() {
		return sex;
	}

	public void setSex(String sex) {
		this.sex = sex;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}


}

这样就会生成tb_user表而且包含父类属性，否则只会生成一张identity表，字段有：id，crearedate,modifydate,name，sex，age