JPA ID Generation Strategies (@GeneratedValue)

In JPA, the @GeneratedValue annotation is used alongside @Id to automatically generate primary key values for entities. Choosing the right ID generation strategy is crucial for database consistency, performance, and scalability in Spring Data JPA and Hibernate applications.

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1. GenerationType.AUTO

JPA provider automatically chooses the most suitable strategy based on the database (could be IDENTITY, SEQUENCE, or TABLE).

Usage:

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

Key Points:

• Default strategy if none is specified.
• Database-independent; works across most databases.
• Good for simple use cases where strict control over ID generation is not required.

Use Case:

Portable applications where you don’t want to worry about database-specific ID generation.

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2. GenerationType.IDENTITY

Uses the database’s auto-increment feature to generate IDs.

Usage:

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

Key Points:

• Supported by most relational databases (MySQL, PostgreSQL, SQL Server).
• The database generates the primary key automatically on insert.
• Simple and widely used.
• Limitation: Not ideal for batch inserts as the key is generated after insertion.

Use Case:

Applications using MySQL or other databases with auto-increment columns.

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3. GenerationType.SEQUENCE

Uses a database sequence object to generate unique IDs.

Usage:

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

Key Points:

• Commonly used in Oracle and PostgreSQL.
• Supports batching efficiently in Hibernate.
• Allows pre-allocation of ID blocks to improve performance.
• Can customize sequence name using @SequenceGenerator.

Example with Custom Sequence:

@Id
@SequenceGenerator(name="user_seq", sequenceName="user_sequence", allocationSize=1)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="user_seq")
private Long id;

Use Case:

Applications needing high-performance inserts with sequence-supporting databases.

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4. GenerationType.TABLE

Uses a separate table to maintain and generate unique IDs.

Usage:

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

Key Points:

• Database-agnostic strategy; works with any relational database.
• Maintains a special table to store the last generated ID.
• Less efficient than IDENTITY or SEQUENCE for high-volume applications.
• Useful for databases without sequence or auto-increment support.

Use Case:

Legacy databases or situations where sequence/identity is not available.

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Comparison Table

Strategy	How It Works	Database Support	Pros	Cons
AUTO	JPA automatically selects a strategy based on the database	All databases	Easy to use, portable across databases	Behavior may vary depending on the DB
IDENTITY	Uses the database’s auto-increment feature	MySQL, SQL Server	Simple, widely supported	Inefficient for batch inserts
SEQUENCE	Uses a database sequence object to generate IDs	Oracle, PostgreSQL	Efficient, supports batch inserts	Requires database sequence support
TABLE	Maintains a separate table to generate IDs	Any database	Works on any DB, database-independent	Slower performance due to extra table lookup

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Best Practices

• AUTO: Use for simple applications needing portability.
• IDENTITY: Use with MySQL/PostgreSQL for auto-increment columns.
• SEQUENCE: Use for sequence-supported databases to optimize performance and batching.
• TABLE: Use only when the database has no native sequence or identity support.

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Conclusion

JPA ID generation strategies allow automatic handling of primary keys in a flexible and database-aware manner. Choosing the right strategy ensures efficient, scalable, and maintainable Spring Data JPA applications.

• AUTO – Simple, portable.
• IDENTITY – Easy, auto-increment.
• SEQUENCE – Efficient for sequence-based databases.
• TABLE – Database-independent, less efficient.

Using these strategies properly eliminates manual key management and simplifies ORM-based development with Hibernate and Spring Data JPA.