Video: (in russian) http://www.youtube.com/watch?v=4pTDhgWW6ko

3. th e?
Scala in a wild
enterprise
Rafael Bagmanov
( Grid Dynamics )

4. In what use cases (types of applications)
does Scala make the least sense?

5. "Database front end, CRUD apps.
Most of the boring apps that are built with
Struts and Spring"
David Pollak
"Barriers to scala adoption" Infoq.com

7. OpenGenesis
github.com/griddynamics/OpenGenesis

8. OpenGenesis
Deployment orchestration tool
● open source - open-genesis.org
● 2 years of development
● > 50 KLOC of scala code
● successfully deployed to production in one
large american financial institution
● Buzzwords: continuous deployment, cloud,
chef, devops, aws, openstack

9. Enterprise characteristics
● Integration with legacy apps and data (lots of
SOAP and xml)
● sophisticated security policies
● IT department separated from development
team
● J2EE Containers everywhere
● Risk averse

10. Typical "lightweight" j2ee stack
Web layer Spring MVC
Service layer Spring
Data access layer
JPA
DB

11. j2ee stack. Scala edition
Web layer Spring MVC + scala magic
Service layer Spring + scala implicits
Data access layer
JPA Squeryl
DB

12. j2ee stack. Scala edition
WAR
Spring MVC
Web layer
Spring
Service layer
Squeryl
Data access layer
DB

13. j2ee stack. Scala edition + scala
goodness
WAR
Spring MVC
Web layer
Akka
Spring
Workflow distributed
Service layer engine
Squeryl
Data access layer
DB

14. Service layer: Spring

15. Spring with scala
● DI fits almost nicely with scala

16. Spring with scala
● DI fits almost nicely with scala
class GenesisRestController {
@Autowired var genesisService: GenesisService = _
}
class GenesisRestController {
@BeanProperty var genesisService: GenesisService = _
}
class GenesisRestController (genesisService: GenesisService) {}

17. Spring with scala
● DI fits almost nicely with scala
○ "Everything is a trait" approach can't be done

18. Spring with scala
● DI fits almost nicely with scala
○ "Everything is a trait" approach can't be done
○ Be aware of type inference in @Configuration bean
trait Service
class ServiceImpl extends Service
@Configuration
class ServiceContext {
@Bean def service = new ServiceImpl
}

19. Spring with scala
● DI fits almost nicely with scala
○ "Everything is a trait" approach can't be done
○ Be aware of type inference in @Configuration bean
trait Service
class ServiceImpl extends Service
@Configuration
class ServiceContext {
@Bean def service: Service = new ServiceImpl
}

20. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.

21. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
springLdapTemplate.authenticate("user", "*", "password", new
AuthenticationErrorCallback {
def execute(e: Exception) {log.error(e)}
})

22. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
springLdapTemplate.authenticate("user", "*", "password", new
AuthenticationErrorCallback {
def execute(e: Exception) {log.error(e)}
})

23. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
springLdapTemplate.authenticate("user", "*", "password", new
AuthenticationErrorCallback {
def execute(e: Exception) {log.error(e)}
})
springLdapTemplate.authenticate("user", "*", "password", log.error(_))

24. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
springLdapTemplate.authenticate("user", "*", "password", log.error(_))
implicit def authErrorCallbackWrapper(func:(Exception) => Any) = {
new AuthenticationErrorCallback {
def execute(exception: Exception): Unit = func(exception)
}
}

25. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
● AOP for free (almost)

26. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
● AOP for free (almost)
○ Be aware of naming in debug info
def findUsers(projectId: Int) {
dao.findUsers(projectId)
}
def findUsers2(projectId: Int) {
dao.allUsers().filter(_.projectId == projectId)
}

27. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
● AOP for free (almost)
○ Be aware of naming in debug info
def findUsers(projectId: Int) { // debugIfo: name "projectId"
dao.findUsers(projectId)
}
def findUsers2(projectId: Int) { // debugInfo: name "projectId$"
dao.allUsers().filter(_.projectId == projectId)
}

28. Spring with scala
● DI fits almost nicely with scala
● Rich spring templates libraries.
● AOP for free (almost)
● Spring security just works

29. Persistence layer: Squeryl

30. Squeryl
● Lightweight ORM written in scala

31. Squeryl
● Lightweight ORM written in scala
class Workflow(override val id: Int) extends KeyedEntity[Int]

32. Squeryl
● Lightweight ORM written in scala
class Workflow(override val id: Int) extends KeyedEntity[Int]
object GS extends Schema {
val workflows = table[Workflow]
}

33. Squeryl
● Lightweight ORM written in scala
class Workflow(override val id: Int) extends KeyedEntity[Int]
object GS extends Schema {
val workflows = table[Workflow]
}
def find(workflowId: Int) = from(GS.workflows)(w =>
where(w.id === workflowId)
select (w)
orderBy(w.id desc)
)

34. Squeryl
● Lightweight ORM written in scala
○ First class support for scala collections, options, etc

35. Squeryl
● Lightweight ORM written in scala
○ First class support for scala collections, options, etc
○ Integrates with spring transaction management
(not out of the box)

36. Squeryl
● Lightweight ORM written in scala
○ First class support for scala collections, options, etc
○ Integrates with spring transaction management
(not out of the box)
@Transactional(propagation = REQUIRES_NEW)
def find(workflowId: Int) = from(GS.workflows)(w =>
where(w.id === workflowId)
select (w)
orderBy(w.id desc)
)

37. Squeryl
● Lightweight ORM written in scala
○ Likes heap in the same proportion as
Hibernate does
hibernate squeryl

38. Squeryl
● Lightweight ORM written in scala
○ Likes heap in the same proportion as
Hibernate does
○ Lot's of "black magic" in source code

39. Squeryl
● Lightweight ORM written in scala
● Internal scala DSL for writing queries
○ Type safe queries - compile time syntax check

40. Squeryl
● Lightweight ORM written in scala
● Internal scala DSL for writing queries
○ Lot's of "black magic" in source code

41. Squeryl
● Lightweight ORM written in scala
● Internal scala DSL for writing queries
○ Lot's of "black magic" in source code
○ Fallback on native sql is not easy

42. Squeryl
● Lightweight ORM written in scala
● Internal scala DSL for writing queries
○ Lot's of "black magic" in source code
○ Fallback on native sql is not easy
○ Lots of implicits drives IDE crazy and
increases compilation time

43. Squeryl
● Lightweight ORM written in scala
● Internal scala DSL for writing queries
○ Lot's of "black magic" in source code
○ Fallback on native sql is not easy
○ Lots of implicits drives IDE crazy and
increase compilation time
○ The approach is somewhat flawed (opinion)

44. Web layer: Spring MVC
lift-json
scala magic

45. Web layer
● RESTfull web services
case class User (
@NotBlank username: String,
@Email @Size(min = 1, max = 256) email: String,
password: Option[String]
)
@Controller
@RequestMapping(Array("/rest/users"))
class UsersController {
@RequestMapping(method = Array(RequestMethod.POST))
@ResponseBody
def create(@RequestBody @Valid request: User): User = userService.create(request)
}

46. Web layer
● RESTfull web services
● Easy to make Hypermedia REST with
implicits
@Controller
@RequestMapping(Array("/rest/users"))
class UsersController {
import com.griddynamics.genesis.rest.links.Hypermedia._
@RequestMapping(method = Array(RequestMethod.POST))
@ResponseBody
def create(@RequestBody @Valid request: User): Hypermedia[User] = {
userService.create(request).withLink("/rest/users", LinkType.SELF)
}

47. Couple of words about
AKKA

48. Ехал Акка через Акка
Смотрит Акка в Акка Акка
Сунул Акка Акка в Акка
Акка Акка Акка Акка *
* Ode to Akka in russian

49. Greatest challenge:

50. Greatest challenge:
People

51. Challenges
● Hiring is hard

52. Challenges
● Hiring is hard
○ Scala is a talent attraction

53. Challenges
● Hiring is hard
○ Scala is a talent attraction
○ In avg: 0.5 interview per month

54. Challenges
● Hiring is hard
● Settling team standards and code
convention

55. Challenges
● Hiring is hard
● Settling team standards and code
convention
○ Tools are not there yet

56. Challenges
● Hiring is hard
● Settling team standards and code
convention
○ Tools are not there yet
○ Between "OCaml" and "Java" fires

57. Challenges
● Hiring is hard
● Settling team standards and code
convention
○ Tools are not there yet
○ Between "OCaml" and "Java" fires
○ "Effective scala" by Twitter and "Scala style guide"
might help (a bit)

58. The greatest code-review mystery of
all times
How to deal with scala.Option
if (option.isDefined) { option match {
case Some(x) => ..
.. case None => ..
?
} }
option.foreach { .. }

59. The greatest code-review mystery of
all times
How to deal with scala.Option
if (option.isDefined) { option match {
case Some(x) => ..
.. case None => ..
?
} }
option.foreach { .. }

60. Recruiting java
developers

61. aka

62. 5 stages of grief

63. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

64. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

65. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

66. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

67. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance

68. 5 stages of grief
1. Denial
2. Anger
3. Bargaining
4. Depression
5. Acceptance