@MappedSuperclass的用法

@MappedSuperclass的用法

@MappedSuperclass的用法 
用在實體的繼承過程中的父類上； 

父類Cat 

package com.xj.model;

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

@MappedSuperclass
public class Cat {
    private Long id;
    private String name;
    @Id
    @GeneratedValue
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
}

子類1 BeijingCat 

package com.xj.model;

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

@Entity
@Table(name="t_beijingcat")
public class BeijingCat extends Cat {
    private String beijing;

    public String getBeijing() {
        return beijing;
    }

    public void setBeijing(String beijing) {
        this.beijing = beijing;
    }

}

子類2 ShanghaiCat 

package com.xj.model;

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

@Entity
@Table(name="t_shanghaiCat")
public class ShanghaiCat extends Cat {
    private String shanghai;

    public String getShanghai() {
        return shanghai;
    }

    public void setShanghai(String shanghai) {
        this.shanghai = shanghai;
    }
}

結果生成 兩張表t_beijingcat、 t_shanghaicat 

如果不用@MappedSuperclass 而用@Entity替換的話，只會生成一張cat表，字段有：id，name，shanghaicat，bejingcat