Les exceptions sont très pratiques pour communiquer que quelque chose s'est mal passé dans un système informatique, mais mal utilisées elles peuvent rendre un système difficile à utilisé et peu fiable.

1. Les exceptions, oui, mais pas
n'importe comment
Charles Desneuf - @SelrahcD - Evaneos

2. function exception_handler($exception) {
$logger->critical($exception);
}
set_exception_handler('exception_handler');

3. public static void main(String[] args) {
try {
// ...
} catch (Exception e) {
logger.critical(e);
}
}

4. 💥

5. // app.log
[2017-07-19 08:11:17] app.CRITICAL: Something really bad occurred {} []

6. 📱

7. 😯

8. $logger->critical($exception);
Application -> logs

9. // class NewsletterService
public function register($email) {
// throw an Exception ?
}

10. 💥

11. // app.log
[2017-07-19 11:12:36] app.CRITICAL: Something really bad occurred {} []

12. 📱

13. 😯

14. 😌

15. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{}

16. 💥

17. // app.log

18. 👌

19. 📅

20. 😒

21. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{}

22. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{
$this->logger->critical($exception);
}

23. 🕒

24. 😴

25. 💥

26. // app.log
[2017-07-19 03:35:17] app.CRITICAL: Something really bad occurred {} []

27. 📱

28. 😯

29. 😤

30. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{
$this->logger->critical($exception);
}

31. 📱

32. 📧

33. 💬

34. 📟

35. 😫

36. 🔕

37. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{
$this->logger->warning($exception);
}

38. 💥

39. // app.log
[2017-07-19 03:35:17] app.WARNING: Something really bad occurred {} []

40. 😴

41. try {
$this->newsletterService->register($email);
}
catch(Exception $exception)
{
$this->logger->warning($exception);
}

42. 📅

43. 💸

44. 🚨

45. try {
$this->newsletterService->register($email);
}
catch(AKnownException $exception)
{
$this->logger->warning($exception);
}

46. try {
$this->newsletterService->register($email);
}
catch(AKnownException $exception)
{
$this->logger->warning($exception);
}
catch(SomeOtherKnownException $exception)
{
$this->logger->warning($exception);
}
catch(YetAnotherKnownException $exception)
{
$this->logger->warning($exception);
}

47. 😅

48. // class NewsletterService
/**
* @throw CouldNotRegisterToNewsletterException
*/
public function register($email) {
// throw an Exception ?
}

49. // NewsletterService::register
try { // … }
catch(AKnownException $exception) {
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}

50. // NewsletterService::register
try { // … }
catch(AKnownException $exception) {
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}

51. // NewsletterService::register
try { // … }
catch(AKnownException $exception) {
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}

52. try {
// ...
}
catch(AKnownException $exception)
{
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}
catch(SomeOtherKnownException $exception)
{
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}
catch(YetAnotherKnownException $exception)
{
throw new CouldNotRegisterToNewsletterException(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}

53. //CouldNotRegisterToNewsletterException
public function static email($email, $exception) {
return new self(
sprintf(‘Could not register %s to newsletter’, $email),
0,
$exception
);
}

54. // NewsletterService::register
try { // … }
catch(AKnownException $exception) {
throw CouldNotRegisterToNewsletterException::email($email,
$exception);
}

55. // NewsletterService::register
try {
// ...
}
catch(AKnownException $exception)
{
throw CouldNotRegisterToNewsletterException::email($email,
$exception);
}
catch(SomeOtherKnownException $exception)
{
throw CouldNotRegisterToNewsletterException::email($email,
$exception);
}
catch(YetAnotherKnownException $exception)
{
throw CouldNotRegisterToNewsletterException::email($email,
$exception);
}

56. 😎

57. try {
$this->newsletterService->register($email);
}
catch(CouldNotRegisterToNewsletterException $exception)
{
$this->logger->warning($exception);
}

58. throw CouldNotRegisterToNewsletterException::email($email, $exception);
Contexte d’implémentation -> Contexte d’utilisation

59. En somme…
• Ne masquez jamais d’exceptions dans le système
• Soyez spécifique à propos des exceptions que vous attrapez
• Souvenez vous que les exceptions sont un moyen de
communication
• Transformez les exceptions d’un contexte à un autre
• Pensez aux niveaux de log et à leur sens
Discussion / Questions / Emoji / Gif de chats: @SelrahcD