how to return not found status from spring controller - spring

Question

I have following spring controller code and want to return not found status if user is not found in database, how to do it?
#Controller
public class UserController {
#RequestMapping(value = "/user?${id}", method = RequestMethod.GET)
public #ResponseBody User getUser(#PathVariable Long id) {
....
}
}

Answer 1

JDK8 approach:
#RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
public ResponseEntity<User> getUser(#PathVariable Long id) {
return Optional
.ofNullable( userRepository.findOne(id) )
.map( user -> ResponseEntity.ok().body(user) ) //200 OK
.orElseGet( () -> ResponseEntity.notFound().build() ); //404 Not found
}

Answer 2

Change your handler method to have a return type of ResponseEntity. You can then return appropriately
#RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
public ResponseEntity<User> getUser(#PathVariable Long id) {
User user = ...;
if (user != null) {
return new ResponseEntity<User>(user, HttpStatus.OK);
}
return new ResponseEntity<>(HttpStatus.NOT_FOUND);
}
Spring will use the same HttpMessageConverter objects to convert the User object as it does with #ResponseBody, except now you have more control over the status code and headers you want to return in the response.

Answer 3

With the latest update you can just use
return ResponseEntity.of(Optional<user>);
The rest is handled by below code
/**
* A shortcut for creating a {#code ResponseEntity} with the given body
* and the {#linkplain HttpStatus#OK OK} status, or an empty body and a
* {#linkplain HttpStatus#NOT_FOUND NOT FOUND} status in case of a
* {#linkplain Optional#empty()} parameter.
* #return the created {#code ResponseEntity}
* #since 5.1
*/
public static <T> ResponseEntity<T> of(Optional<T> body) {
Assert.notNull(body, "Body must not be null");
return body.map(ResponseEntity::ok).orElse(notFound().build());
}

Answer 4

public static ResponseEntity of(Optional body)
A shortcut for creating a ResponseEntity with the given body and the OK status, or an empty body and a NOT FOUND status in case of an Optional.empty() parameter.
#GetMapping(value = "/user/{id}")
public ResponseEntity<User> getUser(#PathVariable final Long id) {
return ResponseEntity.of(userRepository.findOne(id)));
}
public Optional<User> findOne(final Long id) {
MapSqlParameterSource paramSource = new MapSqlParameterSource().addValue("id", id);
try {
return Optional.of(namedParameterJdbcTemplate.queryForObject(SELECT_USER_BY_ID, paramSource, new UserMapper()));
} catch (DataAccessException dae) {
return Optional.empty();
}
}

Answer 5

it could be shorter using Method Reference operator ::
#RequestMapping(value = "/user/{id}", method = RequestMethod.GET)
public ResponseEntity<User> getUser(#PathVariable Long id) {
return Optional.ofNullable(userRepository.findOne(id))
.map(ResponseEntity::ok)
.orElse(ResponseEntity.notFound().build());
}

Answer 6

Need use ResponseEntity or #ResponseStatus, or with "extends RuntimeException"
#DeleteMapping(value = "")
public ResponseEntity<Employee> deleteEmployeeById(#RequestBody Employee employee) {
Employee tmp = employeeService.deleteEmployeeById(employee);
return new ResponseEntity<>(tmp, Objects.nonNull(tmp) ? HttpStatus.OK : HttpStatus.NOT_FOUND);
}
or
#ResponseStatus(value=HttpStatus.NOT_FOUND, reason="was Not Found")