8.12.20 @GeneratedValue
- Organization of this subsection
(1) Description
This annotation specifies the method for automatically generating and allotting a unique value to the primary key column. This annotation is applicable to the field or property of the primary key of entity class or mapped superclass containing @Id.
The primary key value is generated by the following four methods. Depending on the generation method selected, the base table and database sequence object must be prepared beforehand. For details on each of the generation methods, see the description about the strategy element.
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GenerationType.AUTO
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GenerationType.IDENTITY
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GenerationType.SEQUENCE
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GenerationType.TABLE
The applicable targets are method and field.
(2) Element
The following table lists the elements of @GeneratedValue:
|
Element name |
Optional/Required |
Element description |
|---|---|---|
|
Optional |
This element specifies the method for generating the primary key value of the entity class. |
|
|
Optional |
This element specifies the name element set up in @SequenceGenerator or @TableGenerator to be used. |
The details of attributes that are supported with Cosminexus JPA provider are as follows:
(a) strategy element
- Type
-
GenerationType
- Description
-
This element specifies the method for generating the primary key value of the entity class.
The following four types of values can be specified:
-
GenerationType.AUTO
For generating the primary key value, select the most appropriate procedure in each database.
When Oracle or HiRDB is used as the database, the processing is same as GenerationType.TABLE.
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GenerationType.IDENTITY
The primary key value is generated using the identity column of the database.
If Oracle is used as the database, the processing is same as GenerationType.SEQUENCE.
If HiRDB is used as the database, the processing is same as GenerationType.TABLE.
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GenerationType.SEQUENCE
The primary key value is generated using the database sequence object.
If HiRDB is used as the database, the processing is same as GenerationType.TABLE.
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GenerationType.TABLE
The primary key value is generated using a table for maintaining the primary key value.
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- Default value
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GenerationType.AUTO
(b) generator element
- Type
-
String
- Description
-
This element specifies the name element set up in @SequenceGenerator or @TableGenerator to be used.
- Default value
-
The following names are assumed depending on the value of the strategy element:
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In the case of GenerationType.AUTO
"SEQ_GEN"
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In the case of GenerationType.SEQUENCE
"SEQ_GEN_SEQUENCE"
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In the case of GenerationType.TABLE
"SEQ_GEN_TABLE"
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