Java 17: How to resolve NPE when using Optional in a Spring Boot REST controller?
I'm optimizing some code but I'm relatively new to this, so bear with me. Quick question that's been bugging me - I'm working on a Spring Boot application with Java 17, and I've encountered a `NullPointerException` (NPE) when trying to retrieve an optional value in my REST controller. Here’s a simplified version of my code: ```java @RestController @RequestMapping("/api/users") public class UserController { @Autowired private UserService userService; @GetMapping("/{id}") public ResponseEntity<User> getUserById(@PathVariable Long id) { return userService.findById(id) .map(user -> ResponseEntity.ok(user)) .orElseGet(() -> ResponseEntity.notFound().build()); } } ``` And here's my service method: ```java @Service public class UserService { @Autowired private UserRepository userRepository; public Optional<User> findById(Long id) { return userRepository.findById(id); } } ``` The `UserRepository` is an interface extending `JpaRepository<User, Long>`. When I hit the endpoint with an ID that exists in the database, it works fine. However, when the ID does not exist, I get an NPE in the `map` method of the `Optional`. The stack trace indicates that the NPE is triggered at the line where I call `userService.findById(id)`. I’ve also checked the repository implementation and ensured that it correctly returns an empty `Optional` rather than null. I've tried adding logging to see if the ID passed is valid, and it appears to be correct. Additionally, I confirmed that the database connection is functional. Has anyone else faced a similar issue with Optionals in Spring Boot? What could be the reason behind this NPE, and how can I resolve it? Any suggestions or best practices would be appreciated. This is part of a larger web app I'm building. Any help would be greatly appreciated! This is part of a larger service I'm building. I'd be grateful for any help.