Handling an error thrown by a MySQL trigger in Controller class Spring Boot

I'm a bit confused on how to handle the error that my trigger generates in the database. In the future, I plan to add the text of this error to the page on which it was processed. IDEA writes that "Exception 'java.sql.SQLException' is never thrown in the corresponding try block"

@PostMapping("/register")
public String addNewUser(User user, Details details) {
    user.setPassword(passwordEncoder.encode(user.getPassword()));
    user.setRole(Role.USER);
    details.setUser(user);
    user.setDetails(details);
    try {
        userRepository.save(user);
    } catch (SQLException ex) {
        System.out.println(ex.getMessage());
    }

    return "redirect:/";
}