学步园

1、通用方式
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
2 、mysql
 @Id
 @GeneratedValue(strategy = GenerationType.IDENTITY)
3 、oracle
       @Id
       @GeneratedValue(strategy = GenerationType.SEQUENCE,generator="s_gen")
       @SequenceGenerator(name="s_gen",sequenceName="s_seq")