== Why is this an issue?

The request handler function in a `Controller` should set the appropriate HTTP status code based on the operation's success or failure.
This is done by returning a `Response` object with the appropriate status code.

If an exception is thrown during the execution of the handler, the status code should be in the range of 4xx or 5xx.
Examples of such codes are `BAD_REQUEST`, `UNAUTHORIZED`, `FORBIDDEN`, `NOT_FOUND`, `INTERNAL_SERVER_ERROR`, `BAD_GATEWAY`, `SERVICE_UNAVAILABLE`, etc.

The status code should be 1xx, 2xx, or 3xx if no exception is thrown and the operation is considered successful.
Such codes include `OK`, `CREATED`, `MOVED_PERMANENTLY`, `FOUND`, etc.

== How to fix it

=== Code examples

==== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
@Controller
public class UserController {
    public ResponseEntity<User> getUserById(Long userId) {
        try {
            User user = userService.getUserById(userId);
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body(user); // Noncompliant: Setting 500 for a successful operation
        } catch (Exception e) {
            return ResponseEntity.status(HttpStatus.OK).build(); // Noncompliant: Setting 200 for exception
        }
    }
}
----

==== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
@Controller
public class UserController {
    public ResponseEntity<User> getUserById(Long userId) {
        try {
            User user = userService.getUserById(userId);
            return ResponseEntity.ok(user); // Compliant: Setting 200 for a successful operation
        } catch (Exception e) {
            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).build(); // Compliant: Setting 500 for exception
        }
    }
}
----

== Resources

=== Documentation

* https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/HttpStatus.html[Spring Java Documentation - HttpStatus]
* https://docs.spring.io/spring-framework/docs/current/javadoc-api/org/springframework/http/ResponseEntity.html[Spring Java Documentation - ResponseEntity]
* https://docs.spring.io/spring-framework/reference/web/webmvc/mvc-controller/ann-methods/responseentity.html[Spring Framework Documentation - ResponseEntity]
* https://docs.spring.io/spring-framework/reference/web/webmvc/mvc-ann-rest-exceptions.html[Spring Framework Documentation - Exception Handling]

=== Standards

* https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml[IANA - Hypertext Transfer Protocol (HTTP) Status Code Registry]