Hibernate Auto Increment ID

Question

I have a j2ee application using hibernate with annotation  How do I annotate the Id field in my pojo class to set it as auto increment or auto generated  and in adding the bean do I leave that field in my bean null

User · Answer

Hibernate defines five types of identifier generation strategies:

AUTO - either identity column, sequence or table depending on the underlying DB

TABLE - table holding the id

IDENTITY - identity column

SEQUENCE - sequence

identity copy – the identity is copied from another entity

Example using Table

@Id
@GeneratedValue(strategy=GenerationType.TABLE , generator="employee_generator")
@TableGenerator(name="employee_generator", 
                table="pk_table", 
                pkColumnName="name", 
                valueColumnName="value",                            
                allocationSize=100) 
@Column(name="employee_id")
private Long employeeId;

for more details, check the link.

User · Answer

If you have a numeric column that you want to auto-increment  it might be an option to set columnDefinition directly  This has the advantage  that the schema auto-generates the value even if it is used without hibernate  This might make your code db-specific though   import javax persistence Column   Column columnDefinition    serial      postgresql

User · Answer

In case anyone  bumps  in this SO question in search for strategies for Informix table when PK is type Serial   I have found that this works   as an example    Id  GeneratedValue strategy GenerationType IDENTITY   Column name    special serial pk   private Integer special serial pk    For this to work make sure when you do session SaveOrUpdate you pass the value for the column special serial pk NULL     In my case i do an HTML POST with JSON like so        special serial pk   null     lt -- Field to be incremented  specialcolumn1   1   specialcolumn2    I love to code    specialcolumn3   true

User · Answer

Do it as follows  -   Id  GenericGenerator name  kaugen    strategy  increment    GeneratedValue generator  kaugen    Column name  proj id     public Integer getId         return id       You can use any arbitrary name instead of kaugen  It worked well  I could see below queries on console  Hibernate  select max proj id  from javaproj Hibernate  insert into javaproj  AUTH email  AUTH firstName  AUTH lastName  projname          proj id  values

User · Answer

FYI  Using netbeans New Entity Classes from Database with a mysql  auto increment  column  creates you an attribute with the following annotations    Id  GeneratedValue strategy   GenerationType IDENTITY   Basic optional   false   Column name    id    NotNull private Integer id    This was getting me the same an error saying the column must not be null  so i simply removed the  NotNull anotation leaving the attribute null  and it works

User · Answer

Using netbeans New Entity Classes from Database with a mysql auto increment column  creates you an attribute with the following hibernate hbm xml  id is auto increment

User · Answer

Id  GeneratedValue strategy GenerationType AUTO  private int id    and you leave it null  0  when persisting   null if you use the Integer   Long wrappers   In some cases the AUTO strategy is resolved to SEQUENCE rathen than to IDENTITY or TABLE  so you might want to manually set it to IDENTITY or TABLE  depending on the underlying database    It seems SEQUENCE   specifying the sequence name worked for you

[java] Hibernate Auto Increment ID

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