在休眠5之前，

@Entity
@Table(name = "post")
public class Post {

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

    private String title;

    public Post() {}

    public Post(String title) {
        this.title = title;
    }
}

但对于hibernate 5，

@Entity
@Table(name = "post")
public class Post {

    @Id
    @GeneratedValue(
        strategy= GenerationType.AUTO, 
        generator="native"
    )
    @GenericGenerator(
        name = "native", 
        strategy = "native"
    )
    private Long id;

    private String title;

    public Post() {}

    public Post(String title) {
        this.title = title;
    }
}

如果不使用genericgenerator，则在执行多个保存请求时，hibernate将执行以下查询：

SELECT next_val as id_val 
FROM hibernate_sequence FOR UPDATE

UPDATE hibernate_sequence 
SET next_val= 2 where next_val=1

SELECT next_val as id_val 
FROM hibernate_sequence FOR UPDATE

UPDATE hibernate_sequence 
SET next_val= 3 where next_val=1

SELECT next_val as id_val 
FROM hibernate_sequence FOR UPDATE

UPDATE hibernate_sequence 
SET next_val= 4 where next_val=3

INSERT INTO post (title, id) 
VALUES ('High-Performance Java Persistence', 1)

INSERT INTO post (title, id) 
VALUES ('High-Performance Java Persistence', 2)

INSERT INTO post (title, id) 
VALUES ('High-Performance Java Persistence', 3)

所以使用

@GenericGenerator(
    name = "native", 
    strategy = "native"
)

将生成以下查询：

INSERT INTO post (title) 
VALUES ('High-Performance Java Persistence')

INSERT INTO post (title) 
VALUES ('High-Performance Java Persistence')

INSERT INTO post (title) 
VALUES ('High-Performance Java Persistence')

因此，执行更少的查询来执行相同的操作，从而获得高性能。。。

如果手动创建模式，则必须将auto increment属性设置为id列。如果您让hibernate生成您的模式，它将自己生成并设置它。