Spring-data-jpa-duplicate-key-value-violates-unique-constraint May 2026
At the database level, a unique constraint is a fail-safe that ensures data integrity. When Spring Data JPA’s save() or saveAndFlush() method is called, the underlying Hibernate provider generates an INSERT or UPDATE statement. If the database engine (such as PostgreSQL or MySQL) detects that the new data conflicts with an existing entry, it rejects the transaction and throws a low-level error.
If you are manually assigning IDs to entities instead of using @GeneratedValue , you may inadvertently try to reuse an ID that is already present in the table. At the database level, a unique constraint is
In a multi-threaded environment, two processes might check if a value (like an email address) exists at the same time. Both see that it doesn’t, both attempt to insert it, and the second one fails. If you are manually assigning IDs to entities
Spring then catches this vendor-specific SQL exception and wraps it in a DataIntegrityViolationException . This abstraction is helpful for maintaining database-agnostic code, but it requires the developer to look at the "Root Cause" in the stack trace to identify which specific constraint was violated. Common Triggers in Spring Data JPA Spring then catches this vendor-specific SQL exception and
At the database level, a unique constraint is a fail-safe that ensures data integrity. When Spring Data JPA’s save() or saveAndFlush() method is called, the underlying Hibernate provider generates an INSERT or UPDATE statement. If the database engine (such as PostgreSQL or MySQL) detects that the new data conflicts with an existing entry, it rejects the transaction and throws a low-level error.
If you are manually assigning IDs to entities instead of using @GeneratedValue , you may inadvertently try to reuse an ID that is already present in the table.
In a multi-threaded environment, two processes might check if a value (like an email address) exists at the same time. Both see that it doesn’t, both attempt to insert it, and the second one fails.
Spring then catches this vendor-specific SQL exception and wraps it in a DataIntegrityViolationException . This abstraction is helpful for maintaining database-agnostic code, but it requires the developer to look at the "Root Cause" in the stack trace to identify which specific constraint was violated. Common Triggers in Spring Data JPA