Hibernate中用於自動增加MySQL主鍵的Java註釋 - @Id

Question

在這段代碼中，我需要id作爲主鍵，並且它必須遞增。
是ID所需的getter和setter？

@Entity 
public class Contact { 
@Id 
private Integer id; 
private String firstName; 

public Integer getId() { 
    return id; 
} 

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

public String getFirstName() { 
    return firstName; 
} 

public void setFirstName(String firstName) { 
    this.firstName = firstName; 
} 

Answer 1

嘗試使用@GeneratedValue(strategy = GenerationType.IDENTITY)

@Id 
@GeneratedValue(strategy = GenerationType.IDENTITY) 
private Integer id; 

看看在這個文檔約Auto Generated Values

Answer 2

雖然可以使用GenerationType.AUTO，it's not a very good idea for MySQL and Hibernate 5因爲它會默認爲表生成器是bad for performance。

所以，儘管it will disable JDBC batch inserts，你應該使用IDENTITY：

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

，或者你can use native identifier generator which falls back to IDENTITY on MySQL：

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