Auto Primary Key Generator In Hibernate
Apr 02, 2015 hibernate java hibernate tutorial hibernate tutorial by durgasoft hibernate tutorial for beginners hibernate interview questions and answers hibernate mapping tutorial hibernate. Learn about Identity, Sequence, and Table in Hibernate. In my previous post I talked about different database identifier strategies. This post will compare the most common surrogate. =specify autoincrement attribute for primary key. On a further advanced usage, you can make use of TABLE strategy GenerationType.TABLE where you can specify the primary key from a separate table and you can specify this table as @TableGenerator. Hibernate also has a generation strategy: native. It appropriately selects the generation strategy based upon the underlying database's capability.
- Auto Primary Key Generator In Hibernate In Florida
- Auto Primary Key Generator In Hibernate Windows 10
- Auto Primary Key Generator In Hibernate Windows 10
The <generator> class is a sub-element of id. It is used to generate the unique identifier for the objects of persistent class. There are many generator classes defined in the Hibernate Framework.
All the generator classes implements the org.hibernate.id.IdentifierGenerator interface. The application programmer may create one's own generator classes by implementing the IdentifierGenerator interface. Hibernate framework provides many built-in generator classes:
- assigned
- increment
- sequence
- hilo
- native
- identity
- seqhilo
- uuid
- guid
- select
- foreign
- sequence-identity
1) assigned
It is the default generator strategy if there is no <generator> element . In this case, application assigns the id. For example:
2) increment
It generates the unique id only if no other process is inserting data into this table. It generates short, int or long type identifier. If a table contains an identifier then the application considers its maximum value else the application consider that the first generated identifier is 1. For each attribute value, the hibernate increment the identifier by 1. Syntax:
3) sequence
It uses the sequence of the database. if there is no sequence defined, it creates a sequence automatically e.g. in case of Oracle database, it creates a sequence named HIBERNATE_SEQUENCE. In case of Oracle, DB2, SAP DB, Postgre SQL or McKoi, it uses sequence but it uses generator in interbase. Syntax:
For defining your own sequence, use the param subelement of generator.
4) hilo
It uses high and low algorithm to generate the id of type short, int and long. Syntax:
Auto Primary Key Generator In Hibernate In Florida
5) native
It uses identity, sequence or hilo depending on the database vendor. Syntax:
6) identity
Auto Primary Key Generator In Hibernate Windows 10
It is used in Sybase, My SQL, MS SQL Server, DB2 and HypersonicSQL to support the id column. The returned id is of type short, int or long. It is responsibility of database to generate unique identifier.
7) seqhilo
It uses high and low algorithm on the specified sequence name. The returned id is of type short, int or long.
8) uuid
It uses 128-bit UUID algorithm to generate the id. The returned id is of type String, unique within a network (because IP is used). The UUID is represented in hexadecimal digits, 32 in length.
9) guid
| It uses GUID generated by database of type string. It works on MS SQL Server and MySQL. |
10) select
| It uses the primary key returned by the database trigger. |
11) foreign
| It uses the id of another associated object, mostly used with <one-to-one> association. |
12) sequence-identity
| It uses a special sequence generation strategy. It is supported in Oracle 10g drivers only. |
AUTO INCREMENT Field
Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table.
Often this is the primary key field that we would like to be created automatically every time a new record is inserted.
Syntax for MySQL
The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:
Personid int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (Personid)
);
MySQL uses the AUTO_INCREMENT keyword to perform an auto-increment feature.
By default, the starting value for AUTO_INCREMENT is 1, and it will increment by 1 for each new record.
To let the AUTO_INCREMENT sequence start with another value, use the following SQL statement:
To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):
VALUES ('Lars','Monsen');
The SQL statement above would insert a new record into the 'Persons' table. The 'Personid' column would be assigned a unique value. The 'FirstName' column would be set to 'Lars' and the 'LastName' column would be set to 'Monsen'.
Syntax for SQL Server
The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:
Personid int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.
In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record.
Tip: To specify that the 'Personid' column should start at value 10 and increment by 5, change it to IDENTITY(10,5).
To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):
VALUES ('Lars','Monsen');
The SQL statement above would insert a new record into the 'Persons' table. The 'Personid' column would be assigned a unique value. The 'FirstName' column would be set to 'Lars' and the 'LastName' column would be set to 'Monsen'.
Syntax for Access
The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:
Personid AUTOINCREMENT PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);
The MS Access uses the AUTOINCREMENT keyword to perform an auto-increment feature.
By default, the starting value for AUTOINCREMENT is 1, and it will increment by 1 for each new record.
Tip: To specify that the 'Personid' column should start at value 10 and increment by 5, change the autoincrement to AUTOINCREMENT(10,5).
To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):
VALUES ('Lars','Monsen');
The SQL statement above would insert a new record into the 'Persons' table. The 'Personid' column would be assigned a unique value. The 'FirstName' column would be set to 'Lars' and the 'LastName' column would be set to 'Monsen'.
Syntax for Oracle
In Oracle the code is a little bit more tricky.
You will have to create an auto-increment field with the sequence object (this object generates a number sequence).
Use the following CREATE SEQUENCE syntax:
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;
The code above creates a sequence object called seq_person, that starts with 1 and will increment by 1. It will also cache up to 10 values for performance. The cache option specifies how many sequence values will be stored in memory for faster access.
To insert a new record into the 'Persons' table, we will have to use the nextval function (this function retrieves the next value from seq_person sequence):
VALUES (seq_person.nextval,'Lars','Monsen');
Auto Primary Key Generator In Hibernate Windows 10
The SQL statement above would insert a new record into the 'Persons' table. The 'Personid' column would be assigned the next number from the seq_person sequence. The 'FirstName' column would be set to 'Lars' and the 'LastName' column would be set to 'Monsen'.