This document discusses Scala adoption in the enterprise. It describes how Scala was used to build OpenGenesis, an open-source deployment orchestration tool that was successfully deployed in a large financial institution. While Scala works well with common J2EE patterns like Spring MVC, Spring, and JPA/Squeryl, there are challenges around hiring Scala developers and establishing coding standards. The greatest challenges are cultural and involve people.

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

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. ● 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
OpenGenesis
Deployment orchestration tool

9. ● 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
Enterprise characteristics

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

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

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

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

14. Service layer: Spring

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

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

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

18. ● 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
}
Spring with scala

19. ● 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
}
Spring with scala

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

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

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

23. ● 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(_))
Spring with scala

24. ● 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)
}
}
Spring with scala

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

26. ● 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)
}
Spring with scala

27. ● 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)
}
Spring with scala

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

29. Persistence layer: Squeryl

30. ● Lightweight ORM written in scala
Squeryl

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

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

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

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

36. ● Lightweight ORM written in scala
○ First class support for scala collections, options, etc
○ Integrates with spring transaction management
(not out of the box)
Squeryl
@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. ● Lightweight ORM written in scala
○ Likes heap in the same proportion as
Hibernate does
○ Lot's of "black magic" in source code
Squeryl

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

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

41. ● 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
Squeryl

42. ● 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
Squeryl

43. ● 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)
Squeryl

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

45. ● RESTfull web services
Web layer
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. ● RESTfull web services
● Easy to make Hypermedia REST with
implicits
Web layer
@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. ● Hiring is hard
Challenges

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

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

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

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

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

57. ● 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)
Challenges

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

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

60. Recruiting java
developers

61. aka

62. 5 stages of grief

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

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

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

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

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

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