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ID Generation type

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Tags: Spring Boot

The four generation types in Java Spring (Hibernate) are AUTO, IDENTITY, SEQUENCE, and TABLE. Here are the differences between them:

  1. AUTO:

    • The AUTO generation type is the default and allows the persistence provider (e.g., Hibernate) to choose the generation strategy[^3^].

    • When using Hibernate as the persistence provider, AUTO typically defaults to GenerationType.SEQUENCE[^9^].

    • Example:

      @Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
    // ...
}

  2. IDENTITY:

    • The IDENTITY generation type assigns the task of primary key generation to the database[^13^].

    • With this strategy, the database automatically generates the primary key value when inserting a row, so there is no need to specify a value for the ID[^13^].

    • Example:

      @Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;
    // ...
}

  3. SEQUENCE:

    • The SEQUENCE generation type relies on a database sequence to generate unique IDs[^13^].

    • It queries the database for the next sequence value and uses it to insert a row with the corresponding sequence ID[^13^].

    • Example:

      @Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Integer id;
    // ...
}

  4. TABLE:

    • The TABLE generation type uses a database table to generate unique IDs[^13^].

    • It inserts a row into a specific table that maintains a counter for each entity type and uses the generated value as the primary key[^13^].

    • Example:

      @Entity
public class User {
   @Id 
   @GeneratedValue(strategy = GenerationType.TABLE, generator = "table-generator")
   	@TableGenerator(name = "table-generator", table = "ids", pkColumnName = "seq_id", valueColumnName = "seq_value")
   private Integer id;  
   // ...
}

Each generation type has its advantages and considerations. The choice of generation type depends on factors such as database support, performance requirements, and portability concerns[^13^].

GenerationType.IDENTITY relies on an auto-incrementing column in the database, which may cause conflicts if multiple threads try to insert a new row at the same time.

To handle this, you can use GenerationType.SEQUENCE, which uses a database sequence to generate IDs. This strategy is thread-safe because the database ensures that each new ID is unique.

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