Can @PathVariable in Spring Boot Return Null if No Value is Found?

Can @PathVariable in Spring Boot return null if the specified value is not found?

@GetMapping("/users/{id}")
public User getUserById(@PathVariable Long id) {
    return userService.findUserById(id);
}

In Spring Boot, the @PathVariable annotation is used to bind a method parameter to a URI template variable. If the specified variable is not found in the request, it can lead to exceptions rather than simply returning null.

@GetMapping("/users/{id}")
public ResponseEntity<User> getUserById(@PathVariable Optional<Long> id) {
    return userService.findUserById(id.orElse(null))
           .map(ResponseEntity::ok)
           .orElseGet(() -> ResponseEntity.notFound().build());
}

Causes

• The path does not match the expected format, leading to a 404 error.
• The method parameter type does not match the type expected from the request path.

Solutions

• Use optional parameters by wrapping the @PathVariable into an Optional class, e.g., `Optional<Long> id`. This allows handling absent values gracefully.
• Implement exception handling to capture cases where a value is missing and return an appropriate response.

Mistake: Assuming @PathVariable will return null without proper handling.

Solution: Consider using Optional to handle absent values.

Mistake: Not recognizing that a missing path variable will trigger exceptions.

Solution: Implement global exception handling to customize error responses.