What is a good way to handle an Optional object returned by a Spring Data JPA repository in a situation like this?

I am working on a Spring Boot application. Into a service class I have this service method:

@Override
public User getUserById(Integer userId) {
    Optional<User> retrievedUser = this.userRepository.findById(userId);
    return retrievedUser.get();
}

As usual it is calling the Spring Data JPA findById() method returning an Optional object.

I am returning the User object. And here I have the following doubt: if the Optional is empty, it is throwing an exception when I this operation is performed:

retrievedUser.get()

So now…what is the most common way to handle situation like this when I have a Optional object.

The previous service method is called into a controller method implementing an API, this one:

@ApiOperation(
          value = "Retrieve an user by its id", 
          notes = "",
          produces = "application/json")
@GetMapping(value = "/{useridOrEmail}", produces = "application/json")
public ResponseEntity<User> getUserByIdOrEmail(@PathVariable("useridOrEmail") String userIdOrEmail,
                                        @RequestParam(value="isEmail", required = false, defaultValue = "false") boolean isEmail) 
                            throws NotFoundException  {
    
    log.info(String.format("****** Retrieve the user having ID or email: %s *******", userIdOrEmail));
    
    User retrievedUser = null;
    
    if(!isEmail)
        retrievedUser = this.userService.getUserById(Integer.parseInt(userIdOrEmail));
    else
        retrievedUser = this.userService.getUserByemail(userIdOrEmail);
    
    if (retrievedUser == null) {
        String ErrMsg = String.format("The user having ID or email %s was not found", userIdOrEmail);
        
        log.warning(ErrMsg);
        
        throw new NotFoundException(ErrMsg);
    }
        
    return new ResponseEntity<User>(retrievedUser, HttpStatus.OK);
        
}

As you can see in my controller method I am checking if the result of the previous service is null, in case an exception will be thrown. This exception is handled by a class extenging ResponseEntityExceptionHandler in such a way to create a proper response.

So my idea was change my service method putting this retrievedUser.get() operation into a try catch. If I obtain the exception my getUserById() service method will return null and so my controller method will thrown the NotFoundException exception that will be handled returning a specific error response by Spring.

Could be a good solution or exist better way to handle situation like this?

Answer

I would return Optionals from the service then you could chain them real nicely like this:

public ResponseEntity<User> getUserByIdOrEmail(@PathVariable("useridOrEmail") String userIdOrEmail,
                                        @RequestParam(value="isEmail", required = false, defaultValue = "false") boolean isEmail) 
                            throws NotFoundException  {
    
    log.info(String.format("****** Retrieve the user having ID or email: %s *******", userIdOrEmail));
    return fetchUser(userIdOrEmail, isEmail)
           .map((user) -> new ResponseEntity<User>(user, HttpStatus.OK))
           .orElseThrow(() -> new NotFoundException(String.format("The user having ID or email %s was not found", userIdOrEmail)));
}

private Optional<User> fetchUser(String idOrEmail, boolean isEmail) {
    return isEmail 
           ? this.userService.getUserByemail(idOrEmail)
           : this.userService.getUserById(Integer.parseInt(idOrEmail));
}

And logging the warning should be handled in a common exception handler which logs all the Not Found’s similar way.