Main problems with legacy applications. Presentation from JAX 2015.

1. Legacy Sins
Eberhard Wolff
Freelancer

2. Eberhard Wolff - @ewolff
I’m a Software
Architect.
But I’m not doing
architecture. !

3. Eberhard Wolff - @ewolff
How important is
Software
Architecture?

4. Eberhard Wolff - @ewolff
Why would we
care about
Software
Architecture?

5. Eberhard Wolff - @ewolff
Software
Architecture
=Structure

6. Eberhard Wolff - @ewolff
Architecture Goals: Quality
• All kinds of quality
• Performance
• Security
• …
• Focus of this presentation:
Changeability
• Architects must understand
customers & priority

7. Eberhard Wolff - @ewolff
Architects must
understand
customer

8. Eberhard Wolff - @ewolff
Software Architecture
Set of
structures
comprise
software elements,
relations among them, and
properties of both.

9. Eberhard Wolff - @ewolff
Why?
• Can work on modules in isolation
• Can work on collaboration of
modules
• Fits in my head
• Dan North

10. Eberhard Wolff - @ewolff
Does He Care?

11. Eberhard Wolff - @ewolff
Why?
Great
Architecture
Software
Easy to change
High
productivity
Low
Cost

12. Eberhard Wolff - @ewolff
He Cares
€

13. Eberhard Wolff - @ewolff
Why?
Great
Architecture
Software
Easy to change
High
productivity
Low
Cost

14. Eberhard Wolff - @ewolff
What He Cares About
Great
Architecture
Software
Easy to change
High
productivity
Low
Cost

15. Eberhard Wolff - @ewolff
Is architecture
the only factor
for
changeability?

16. Eberhard Wolff - @ewolff
What is the
worst thing
we can have in
a legacy code?

17. Eberhard Wolff - @ewolff
Great
architecture
or
automated
tests?

18. Eberhard Wolff - @ewolff
No Automated Tests Worse
• No way to find bugs
• Changes almost impossible
• Legacy code = code without tests
• Michael Feathers
Working Effectively with Legacy
Code

19. Eberhard Wolff - @ewolff
Let’s add
some
automated
GUI tests

20. Eberhard Wolff - @ewolff
Automated GUI Tests
• Easy to implement
• Exactly what testers do manually
• Easy to understand for customers
• Test business processes
• Safety net

21. Eberhard Wolff - @ewolff
Unit Tests
or automated
GUI tests?

22. Eberhard Wolff - @ewolff
Many GUI Tests Worse
• Fragile: Changes to GUI break test
• Business meaning of tests easily lost
• Takes long
• Often not reproducible

23. Eberhard Wolff - @ewolff
Automated
GUI Tests
Automated
Integration
Tests
Unit
Tests
Manual Tests

24. Eberhard Wolff - @ewolff
Automated
GUI Tests
Automated
Integration
Tests
Unit
Tests
Manual Tests

25. Eberhard Wolff - @ewolff
Slow
Unreliable
Expensive

26. Eberhard Wolff - @ewolff
Alternatives to
automated
GUI tests?

27. Eberhard Wolff - @ewolff
Textueller
Akzeptanztest

28. Eberhard Wolff - @ewolff
Szenario
• Möglicher Ablauf in einer Story
• Standardisierte Bestandteile:
• Gegeben... (Kontext)
• Wenn... (Ereignis)
• Dann... (erwartetes Ergebnis)

29. Eberhard Wolff - @ewolff
Szenario: Beispiel
Szenario: Kunde registriert sich erfolgreich
Gegeben ein neuer Kunde mit EMail
eberhard.wolff@gmail.com Vorname Eberhard Name
Wolff
Wenn der Kunde sich registriert
Dann sollte ein Kunde mit der EMail
eberhard.wolff@gmail.com existieren
Und es sollte kein Fehler gemeldet werden
Kontext
Ereignis
Erwartetes
Ergebnis
Erwartetes
Ergebnis

30. Eberhard Wolff - @ewolff
public class UserRegistrationSteps {
private RegistrationService registrationService;
private User kunde;
private boolean fehler = false;
// Initialisierung des RegistrationService ausgelassen
@Given(
"ein neuer Kunde mit EMail $email Vorname $vorname“ +
"Name $name")
public void gegebenKunde(String email, String vorname,
String name) {
kunde = new User(vorname, name, email);
}

31. Eberhard Wolff - @ewolff
@When("der Kunde sich registriert")
public void registerKunde() {
try {
registrationService.register(kunde);
} catch (IllegalArgumentException ex) {
fehler = true;
}
}
@Then("sollte ein Kunde mit der EMail $email existieren")
public void existiert(String email) {
assertNotNull(registrationService.getByEMail(email));
}
@Then("es sollte kein Fehler gemeldet werden")
public void keinFehler() {
assertFalse(fehler);
} }

32. Eberhard Wolff - @ewolff
Test is about
handling risk

33. Eberhard Wolff - @ewolff
Tests for Risks
• Algorithm / calculation wrong:
Unit test
• System failures: Unit tests
• Wiring / collaboration:
Integration tests
• Business process: Integration test
• GUI: GUI test

34. Eberhard Wolff - @ewolff
Example: User Registration
• Unit test
Validations
Database failure
• Integration test
Process
• GUI test
Everything displayed?

35. Eberhard Wolff - @ewolff
Not Tested
• GUI won’t test validation
• …or algorithms
• …or the process
• Risks handled elsewhere

36. Eberhard Wolff - @ewolff
Automated
GUI Tests
Automated
Integration
Tests
Unit
Tests
Manual Tests

37. Eberhard Wolff - @ewolff
Automated
GUI Tests.
Automated
Integration
Tests
Unit
Tests
Manual
Tests
Test Pyramid

38. Eberhard Wolff - @ewolff
Test Pyramid
instead of
Automated
GUI tests

39. Eberhard Wolff - @ewolff
Great
architecture
or fast & easy
deployment?

40. Eberhard Wolff - @ewolff
Deployment
• Manual deployment is error prone
• Slow deployment
Lots of code developed but not
deployed
i.e. more lean waste
Slow feedback
Slow time to recovery

41. Eberhard Wolff - @ewolff
Leseprobe:
http://bit.ly/CD-Buch

42. Eberhard Wolff - @ewolff
Continuous Delivery:
Build Pipeline
Commit
Stage
Automated
Acceptance
Testing
Automated
Capacity
Testing
Manual
Explorative
Testing
Release

43. Eberhard Wolff - @ewolff
Continuous Delivery
• Testing
• + automated deployment
• Testing: reduce probability of errors
• Automated deployment: better
mean time to repair

44. Eberhard Wolff - @ewolff
Continuous Delivery
• Make software easier to change
• & deploy
• Reliable and reproducible tests
• Automated deployed
• Fast & reliable

45. Eberhard Wolff - @ewolff
What is a great
architecture?

46. Eberhard Wolff - @ewolff
GUI
Logic
Database

47. Eberhard Wolff - @ewolff
Is 3 Tier a
great
architecture?

48. Eberhard Wolff - @ewolff
3 Tier
• Actually layer: no distribution
• By technology
• Layers can be replaced
• Layers can be developed
independently

49. Eberhard Wolff - @ewolff
Do you replace
e.g. the
persistence
layer?

50. Eberhard Wolff - @ewolff
Is it really
simple to add
e.g. mobile
clients?

51. Eberhard Wolff - @ewolff
A better
reason:
Fits in my
head.

52. Eberhard Wolff - @ewolff
Redo the
order
processing!

53. Eberhard Wolff - @ewolff
Add this to
the
registration!

54. Eberhard Wolff - @ewolff
Can we change
the
persistence
technology
instead?

55. Eberhard Wolff - @ewolff
Please

56. Eberhard Wolff - @ewolff
What is a
persistence
technology??

57. Eberhard Wolff - @ewolff
Registration Order Billing
GUI
Logic

58. Eberhard Wolff - @ewolff
Architecture
• Should support changes
• …with business value
• Needs to model the domain
• Hard to get right
• Architect needs to understand the
domain

59. Eberhard Wolff - @ewolff
Is a great
architecture
free of cyclic
dependencies?

60. Eberhard Wolff - @ewolff
A B
A depends on B
Changes to B influence A

61. Eberhard Wolff - @ewolff
A B
A depends on B
Changes to B influence A
B depends on A
Changes to A influence B
In fact one component
Should be two components

62. Eberhard Wolff - @ewolff
Is a great
architecture
free of cyclic
dependencies?

63. Eberhard Wolff - @ewolff
Cyclic
dependencies:
architects’
mortal sin

64. Eberhard Wolff - @ewolff
A B
A B
42
2
200

65. Eberhard Wolff - @ewolff
Other Architecture Metrics
• High cohesion
Elements of a module should belong
together
• Low coupling
Modules should not depend on each
other

66. Eberhard Wolff - @ewolff
Great Architecture
• Don’t overrate cyclic dependencies!
• Consider other metrics
• Architecture by domain

67. Eberhard Wolff - @ewolff
The worst
legacy
problems?

68. Eberhard Wolff - @ewolff
The project has a
lot of cyclic
dependencies!
I know.
…but that doesn’t
cause a lot of trouble

69. Eberhard Wolff - @ewolff
Architects must
understand
customer & his
quality demands

70. Eberhard Wolff - @ewolff
Quality
• Changeability
• Performance
• Security
• …

71. Eberhard Wolff - @ewolff
No two
projects are
alike.

72. Eberhard Wolff - @ewolff
No general
rules.

73. Eberhard Wolff - @ewolff
Sorry!

74. Eberhard Wolff - @ewolff
Software
Easy to change
Automated
tests
Test
pyramid
Fast & easy
deployment
Great
Architecture
No cyclic
dependencies
Low
coupling
High
cohesion

75. Eberhard Wolff - @ewolff
I’m a Software
Architect.
But I’m not doing
architecture.
There is more
to changeable
software than
architecture.

76. Eberhard Wolff - @ewolff
Thank You!