Most developers prefer to spend their time writing code instead of performing build script maintenance. Build scripting may be an essential part of the software development process, but it often lacks maintainability which makes applying and deploying changes a tedious job. So it’s important to make sure your build system encourages simplicity and that changes can be made in a fast and straightforward way. Industry standards Ant and Maven are not quite up to the task; Gradle is a better alternative. This presentation introduces Gradle – a modern build system that supports all JVM Languages – and shares the result of the Ant-to-Gradle migration that was performed at NS (Dutch Railways). The session will focus on the challenges we faced while trying to replace Ant scripting with the Gradle equivalent and how we handled them. After attending this session, you will have a good understanding of Gradle and its pros and cons compared to Ant and Maven. On top of that, you will be able to migrate your own project to Gradle, even if your project has a huge code base or relies on ancient technologies. The lessons we learnt at NS could be very helpful to your own situation.

2. Who is this guy?

7. We will consult these 3 experts
Linus Torvalds
creator of Linux & Git

8. We will consult these 3 experts
Linus Torvalds Mark Reinhold
creator of Linux & Git Java's chief architect

9. We will consult these 3 experts
Linus Torvalds Mark Reinhold Louis van Gaal
creator of Linux & Git Java's chief architect manager of
Manchester United

10. We will consult these 3 experts
Linus Torvalds Mark Reinhold Louis van Gaal
creator of Linux & Git Java's chief architect former manager of
Manchester United

11. Changes in
requirements

12. Changes in requirements
Past
compiling
packaging

13. Changes in requirements
Present
one project, multiple programming languages
compiling
running automated tests
packaging
integrating code as early as possible
deploying software to TAP

14. Defining builds in
XML

15. XML
Let's start by being nice:
excels at expressing hierarchical data

16. XML
Let's start by being nice:
excels at expressing hierarchical data
but...
build scripting logic doesn't easily fit a hierarchy
often it consists of conditional and repeating logic
which can be expressed more concisely in a programming
language

17. What does Linus think of XML?

18. What does Linus think of XML?
( )
XML is crap. Really. There are no excuses.
XML is nasty to parse for humans, and it's a
disaster to parse even for computers. There's
just no reason for that horrible crap to exist.
https://plus.google.com/+LinusTorvalds/posts/X2XVf9Q7MfV

19. Build tools:
head to head

20. Ant vs. Maven according to Mark

21. Ant vs. Maven according to Mark
( )
What's the difference between Ant and
Maven?
https://www.parleys.com/tutorial/devoxx-fireside-chat

22. Ant vs. Maven according to Mark
( )
What's the difference between Ant and
Maven? The creator of Ant has apologized.
https://www.parleys.com/tutorial/devoxx-fireside-chat

23. Build tools head-to-head
Ant Maven Gradle

24. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL

25. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in

26. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple

27. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple
pre-defined structure absent present present

28. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple
pre-defined structure absent present present
custom structure n/a complex simple

29. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple
pre-defined structure absent present present
custom structure n/a complex simple
verbosity high average low

30. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple
pre-defined structure absent present present
custom structure n/a complex simple
verbosity high average low
learning curve shallow steep average

31. Build tools head-to-head
Ant Maven Gradle
build script format XML XML Groovy / DSL
dependencies with Ivy built-in built-in
multi-module builds complex simple simple
pre-defined structure absent present present
custom structure n/a complex simple
verbosity high average low
learning curve shallow steep average
build order depends-on lifecycles directed acyclic graph

32. Gradle at NS
(Dutch Railways)

33. Gradle at NS (Dutch Railways)
not at all a 'greenfield project'!
1 million lines of code
over 25,000 lines of Ant scripting
30 software developers
system behaves like a monolith

34. Migration strategy

35. Migration strategy
divide the project into components according to
functionality
start Gradling at a small, isolated part
focus on code that is used regularly (i.e. on a daily basis)

36. Migration strategy
divide the project into components according to
functionality
start Gradling at a small, isolated part
focus on code that is used regularly (i.e. on a daily basis)
verify after each step that:
results are exactly the same as before
no problems occur in existing Ant code

37. Migration strategy
divide the project into components according to
functionality
start Gradling at a small, isolated part
focus on code that is used regularly (i.e. on a daily basis)
verify after each step that:
results are exactly the same as before
no problems occur in existing Ant code
don't fool yourself: not every single line of Ant code should
be replaced
Ant projects are 'first class citizens'

38. Challenges
dependency spaghetti
collaboration with existing Ant code
continuous integration & delivery

39. Migration result
a component's responsibility has become clearer
a build will only run if the particular component has
changed
run unit test in parallel (Gradle decides when)
dependencies behave transitively

40. Migration result (lines of code)
Language Lines of code (before) Lines of code (after)
Ant over 25,000 about 15,000
Gradle 0 1,232

41. What does Louis think of migrating all Ant
code?

42. What does Louis think of migrating all Ant
code?
( )
In the Netherlands they say: "That is another
cook."
https://youtu.be/x-QRqOndbzw

43. Wrap-up

44. Wrap-up

45. Wrap-up
Ant & Maven:
require hard-to-maintain code
the purpose of a code fragment is not clearly evident

46. Wrap-up
Ant & Maven:
require hard-to-maintain code
the purpose of a code fragment is not clearly evident
often fail to address changing requirements
rely heavily on XML

47. Wrap-up
Ant & Maven:
require hard-to-maintain code
the purpose of a code fragment is not clearly evident
often fail to address changing requirements
rely heavily on XML
Gradle is a better alternative

48. Wrap-up (2)
Gradle offers structure and flexibility
tries to combine the power of Ant and Maven
integrates with (almost) anything

49. Wrap-up (3)
So no drawbacks whatsoever?

50. Wrap-up (3)
So no drawbacks whatsoever?
Gradle spends a lot of time on configuration parsing (but
this has steadily improved in the past year)
developers need to get used to it
migrating existing scripting is a lot of work

51. Should my project use Gradle?
A brand-new project?

52. Should my project use Gradle?
A brand-new project?
just do it

53. Should my project use Gradle?
A brand-new project?
just do it
do it RIGHT NOW

54. Should my project use Gradle?
An existing project?

55. Should my project use Gradle?
An existing project?
Will you benefit from Gradles key features? (better
performance, maintainability, less verbose, ...)

56. Should my project use Gradle?
An existing project?
Will you benefit from Gradles key features? (better
performance, maintainability, less verbose, ...)
Any technical debt to solve?

57. Should my project use Gradle?
An existing project?
Will you benefit from Gradles key features? (better
performance, maintainability, less verbose, ...)
Any technical debt to solve?
use an artifact repository and remove duplicates
divide your project into multiple components
define a clear structure in your build logic

58. Any questions?

59. Further reading
"Why Build Your Java Projects with Gradle Rather than Ant
or Maven?"
by Benjamin Muschko
( )
Gradle User Guide
( )
Gradle Build Language Reference
( )
http://www.drdobbs.com/jvm/why-build-your-java-projects-with-gradle/240168608
http://gradle.org/docs/current/userguide/userguide.html
http://gradle.org/docs/current/dsl/index.html

60. Thank you :)
You can contact me at:
@hannotify
hanno.embregts@infosupport.com