Spring Data/JPA - How can I check if a record already exists by name?

Question

I have a question with Spring Data/JPA, I would like to know if there is any way to check if a name is already registered in the database with some function in the Repository with parameters.

I have the idea of ​​using a boolean, but I don't know how to execute it correctly to get the expected result.

@Query(nativeQuery= true, value="SELECT first_name FROM students WHERE first_name = :firstname")
boolean findByFirstname(String firstname);

Answer 1

Boolean return type for an EXISTS style query is not supported by JPA.

However, you can work around this by creating a default method that has the signature you want and that calls the JPA method.

default boolean existsByFirstname(String firstname) {
    return !findByFirstname(firstname).isEmpty();
}
    
@Query(nativeQuery= true, value="SELECT first_name FROM students WHERE first_name = :firstname")
List<String> findByFirstname(String firstname);