package net.jeffrey.hibernate;import javax.persistence.GeneratedValue;import javax.persistence.GenerationType;import javax.persistence.Id;import javax.persistence.MappedSuperclass;/** * 實體類的抽象基類，定義了id字段 * @author jeffrey */@MappedSuperclasspublic abstract class AbstractEntity {    @Id @GeneratedValue(strategy = GenerationType.AUTO)    protected Integer id;    public Integer getId() {        return id;    }    public void setId(Integer id) {        this.id = id;    }}