The document discusses various topics related to persistence in Scala, including: - Setting focus on the persistence layer and introducing some of the many alternatives. - Thinking carefully about the choices made regarding persistence. - How Scala extends and improves upon concepts from Java, such as null safety with Option types, extension methods, and powerful collections.

1. Persistens i Scala
JavaZone X
Trond Marius Øvstetun
© Mesan AS

2. Agenda
• Sette fokus på persistens‐laget
• Det finnes mange alternativer!
• En liten introduksjon
© Mesan AS

3. Agenda
• Sette fokus på persistens‐laget
• Det finnes mange alternativer!
• En liten introduksjon
• Tenke seg om i de valgene man gjør
© Mesan AS

4. Trond Marius Øvstetun
• Seniorkonsulent og
fagleder i Mesan
• Lidenskapelig utvikler,
arkitekt, teamleder ++
• Java, Scala, HTML/js
• Alltid på jakt etter bedre,
enklere måter
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5. Mesan
... når standardsystemer ikke er nok
• Systemutvikling – skreddersøm
• Løsningsfokus
• “Store” systemer
• Transaksjonssystemer
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6. Mesan
... når standardsystemer ikke er nok
• Systemutvikling – skreddersøm
• Løsningsfokus
• “Store” systemer
• Transaksjonssystemer
• Lang levetid – langsiktighet
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7. Levetid
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8. Systemer i endring
V1 V2 V3 V4 V5 V6
DB
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9. Systemer i endring
Forretningsprosesser
V1 V2 V3 V4 V5 V6
DB
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10. Systemer i endring
Forretningsprosesser
V1 V2 V3 V4 V5 V6 V7
T1 T2 T3 T4 T5 T6
DB
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11. Systemer i endring
Forretningsprosesser
V1 V2 V3 V4 V5 V6 V7
T1 T2 T3 T4 T5 T6
Teknologi
DB
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12. Systemer i endring
Forretningsprosesser
V1 V2 V3 V4 V5 V6 V7 V8 V9
F1 F2 F3 F4 F5 F6 F7
T1 T2 T3 T4 T5 T6
DB
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13. Java -> Scala
Teknologien driver oss
Hva man sitter igjen med etter introduksjonen...
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14. • De fleste som prøver Scala har bakgrunn fra Java
• Innarbeidede rutiner, forventninger, perferanser,
tankesett, rammeverk etc
• Objektorientert?
• Transaksjonsskript?
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15. Person
firstname : String
lastname : String
birthDate : Date
gender : Gender
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16. public class Person {
private String firstname;
private String lastname;
private Date birthDate;
private Gender gender;
public Person(String firstname, String lastname, Gender gender, Date birthDate) {
this.firstname = firstname;
this.lastname = lastname;
this.gender = gender;
this.birthDate = birthDate;
}
public String getFirstname() {
return firstname;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public Date getBirthDate() { Person
return birthDate;
} firstname : String
public void setBirthDate(Date birthDate) {
lastname : String
this.birthDate = birthDate;
} birthDate : Date
gender : Gender
public Gender getGender() {
return gender;
}
public void setGender(Gender gender) {
this.gender = gender;
}
}
© Mesan AS

17. public class Person {
private String firstname;
private String lastname;
private Date birthDate;
private Gender gender;
public Person(String firstname, String lastname, Gender gender, Date birthDate) {
this.firstname = firstname;
this.lastname = lastname;
this.gender = gender;
this.birthDate = birthDate;
}
public String getFirstname() {
return firstname;
}
class Person(var firstname:String, var lastname:String,
public void setFirstname(String firstname) {
this.firstname = firstname; var gender:Gender, var birthdate:Date)
}
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public Date getBirthDate() { Person
return birthDate;
} firstname : String
public void setBirthDate(Date birthDate) {
lastname : String
this.birthDate = birthDate;
} birthDate : Date
gender : Gender
public Gender getGender() {
return gender;
}
public void setGender(Gender gender) {
this.gender = gender;
}
}
© Mesan AS

18. null? Nei takk
• Option[T]
• Some – innhold
• None
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19. null? Nei takk
• Option[T]
• Some – innhold class Person(var firstname:String, var lastname:String,
var gender:Gender, var birthdate:Option[Date] = None)
• None
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20. null? Nei takk
• Option[T]
• Some – innhold class Person(var firstname:String, var lastname:String,
var gender:Gender, var birthdate:Option[Date] = None)
• None
interface PersonRepository {
/**
* @return A person if found, <code>null</code> otherwise.
*/
Person findById(int id);
}
PersonRepository repo;
Person person = repo.findById(1);
if (person != null) {
person.updateThySelf();
}
PersonRepository repo;
Person person = repo.findById(1);
if (person != null) {
return person.firstname + " " + person.lastname;
} else {
return "John Doe"
}
© Mesan AS

21. null? Nei takk
• Option[T]
• Some – innhold class Person(var firstname:String, var lastname:String,
var gender:Gender, var birthdate:Option[Date] = None)
• None
interface PersonRepository {
/**
* @return A person if found, <code>null</code> otherwise.
trait PersonRepository {
*/
def findById(id:Int) : Option[Person]
Person findById(int id);
}
}
PersonRepository repo;
Person person = repo.findById(1); val repo:PersonRepository
if (person != null) { val p = repo.findById(1)
person.updateThySelf(); for (person <- p) {
} person.updateThySelf()
}
PersonRepository repo;
Person person = repo.findById(1); val repo:PersonRepository
if (person != null) {
val p = repo.findById(1)
return person.firstname + " " + person.lastname; p.map(person =>
} else {
person.firstname + " " + person.lastname)
return "John Doe" .getOrElse("John Doe")
}
© Mesan AS

22. Statisk, men “dynamisk”
• Scala er utvidbart
"(d)*".r => Regex
"123".toInt => Int(123)
• “Pimp My Library” "hello %s".format("world") => String("hello world")
"hello".capitalize => "Hello"
• Utvider vanlige klasser
med metoder 1 to 10 => Range(1, 10)
1 until 10 => Range(1, 9)
• Mye i vanlige bibliotek
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23. Statisk, men “dynamisk”
• Scala er utvidbart
"(d)*".r => Regex
"123".toInt => Int(123)
• “Pimp My Library” "hello %s".format("world") => String("hello world")
"hello".capitalize => "Hello"
• Utvider vanlige klasser
med metoder 1 to 10 => Range(1, 10)
1 until 10 => Range(1, 9)
• Mye i vanlige bibliotek
implicit def strToFoo(in:String) : Foo = new Foo(in)
class Foo(f:String) {
def bar = f + "bar"
• Roll your own! }
"foo".bar => "foobar"
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24. Avanserte strukturer
val persons = List(Person("Per"), Person("Pål"), Person("Espen"))
val (lucky, unlucky) = persons.partition(_.name == "Espen")
val fullnames = persons.map(_.name + " Askeladd")
for (n <- fullnames) {
println(n)
}
© Mesan AS

25. Avanserte strukturer
val persons = List(Person("Per"), Person("Pål"), Person("Espen"))
val (lucky, unlucky) = persons.partition(_.name == "Espen")
• Scala collections er val fullnames = persons.map(_.name + " Askeladd")
kraftig kost for (n <- fullnames) {
println(n)
}
© Mesan AS

26. Avanserte strukturer
val persons = List(Person("Per"), Person("Pål"), Person("Espen"))
val (lucky, unlucky) = persons.partition(_.name == "Espen")
• Scala collections er val fullnames = persons.map(_.name + " Askeladd")
kraftig kost for (n <- fullnames) {
println(n)
}
• Tuppler val navn = ("Trond Marius", "Øvstetun")
© Mesan AS

27. Avanserte strukturer
val persons = List(Person("Per"), Person("Pål"), Person("Espen"))
val (lucky, unlucky) = persons.partition(_.name == "Espen")
• Scala collections er val fullnames = persons.map(_.name + " Askeladd")
kraftig kost for (n <- fullnames) {
println(n)
}
• Tuppler val navn = ("Trond Marius", "Øvstetun")
case class MyVal(s:String)
def myMatch(n:Any) : String = {
n match {
• Pattern matching case 1 => "ONE"
case n:Int if n < 10 => "low..."
ruler! case n:Int if n > 10 => "high!"
case p:Person => "a person: " + p.firstname
case MyVal(s) => s
}
}
© Mesan AS

28. Objekter? Funksjoner?
• Høyereordens funksjoner – gjenbruk og abstraksjon
• Immutable datastrukturer – sikkerhet
• case class ‐> copy(...)
• Minimalisere API og API‐bruk, spesialisere tjenester
• Klar og konsistent kode
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29. The selling point
“Slapp av – Alle java‐biblioteker og APIer
fungerer med Scala!”
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30. The selling point
“Slapp av – Alle java‐biblioteker og APIer
fungerer med Scala!”
Men er det så enkelt?
© Mesan AS

31. En typisk applikasjon
Brukergrensesnitt
Visningslogikk
Forretningslogikk
Data aksess
DB
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32. En typisk applikasjon
Brukergrensesnitt
Visningslogikk
Domene Forretningslogikk
Data aksess
DB
© Mesan AS

33. En typisk java-
HTML / Javascript
Spring MVC
@Controller
@Entity
JPA Spring
@Service
Spring / JPA
@Repository
DB
© Mesan AS

34. En enkel datamodell
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

35. JPA
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

36. Vi mapper en sang
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

37. Vi mapper en sang
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

38. Vi mapper en sang
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

39. Vi mapper en sang
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song(@Id @GeneratedValue(strategy = GenerationType.IDENTITY) var id:Int,
var name:String, var duration:Int, var tracknumber:Int)
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

40. Vi mapper en sang
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song(var id:Int, var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song(@Id @GeneratedValue(strategy = GenerationType.IDENTITY) var id:Int,
var name:String, var duration:Int, var tracknumber:Int)
@Entity
class Song {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var name : String = _
var duration : Int = _
var tracknumber : Int = _
}
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

41. Et album
@Entity
class Album {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var name : String = _
@Temporal(value = TemporalType.DATE)
var release : Date = _
var rating : Int = _
}
Album
name : String
release : Date
rating : Option[Int]
1
*
«enumeration»
Artist
Genre
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

42. Et album
@Entity
class Album {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var name : String = _
@Temporal(value = TemporalType.DATE)
var release : Date = _
var rating : Int = _
}
Album
– med sanger name : String
release : Date
rating : Option[Int]
1
import java.util.{List => jList}
@OneToMany(orphanRemoval = true)
@JoinColumn(name = "album_id")
@OrderBy("tracknumber") *
«enumeration»
Genre
Artist var songs : jList[Song] = _
Song
Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
name : String
duration : Int
*
* Song
trackNumber : Int
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

43. Artister
@Entity
class Artist {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var name : String = _
var biography : String = _
@Temporal(value = TemporalType.DATE)
var founded : Date = _
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

44. @Entity
Artister
class Artist {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var name : String = _
var biography : String = _
@Temporal(value = TemporalType.DATE)
var founded : Date = _
}
@OneToMany(orphanRemoval = true,
cascade = Array(CascadeType.ALL))
@JoinColumn(name = "artist_id")
var albums : jList[Album] = _
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

45. @Entity
Artister
class Artist {
«enumeration»
@Id Genre
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _ Rock
var name : String = _ Pop
var biography : String = _ Classic
@Temporal(value = TemporalType.DATE) Blues
var founded : Date = _ Rap
}
HipHop
Alternative
@OneToMany(orphanRemoval = true,
cascade = Array(CascadeType.ALL))
@JoinColumn(name = "artist_id")
var albums : jList[Album] = _
object Genre extends Enumeration {
type Genre = Value
val Rock = Value(1)
val Pop = Value(2)
val Classic = Value(3)
val Blues = Value(4)
val Rap = Value(5)
val HipHop = Value(6)
val Alternative = Value(7)
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

46. @Entity
Artister
class Artist {
«enumeration»
@Id Genre
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _ Rock
var name : String = _ Pop
var biography : String = _ Classic
@Temporal(value = TemporalType.DATE) Blues
var founded : Date = _ Rap
}
HipHop
Alternative
@OneToMany(orphanRemoval = true,
cascade = Array(CascadeType.ALL))
@JoinColumn(name = "artist_id")
var albums : jList[Album] = _
object Genre extends Enumeration {
type Genre = Value
@Enumerated
var maingenre : Genre = Genre.Rock val Rock = Value(1)
val Pop = Value(2)
val Classic = Value(3)
val Blues = Value(4)
val Rap = Value(5)
val HipHop = Value(6)
val Alternative = Value(7)
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

47. @Entity
Artister
class Artist {
«enumeration»
@Id Genre
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _ Rock
var name : String = _ Pop
var biography : String = _ Classic
@Temporal(value = TemporalType.DATE) Blues
var founded : Date = _ Rap
}
HipHop
Alternative
@OneToMany(orphanRemoval = true,
cascade = Array(CascadeType.ALL))
@JoinColumn(name = "artist_id")
var albums : jList[Album] = _
object Genre extends Enumeration {
@Converter(name = "GenreConverter", type Genre = Value
converterClass = classOf[GenreConverter])
@Convert("GenreConverter") val Rock = Value(1)
var maingenre : Genre = Genre.Rock val Pop = Value(2)
val Classic = Value(3)
val Blues = Value(4)
val Rap = Value(5)
val HipHop = Value(6)
val Alternative = Value(7)
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

48. Artister med personer
@Entity
class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var firstname : String = _
var lastname : String = _
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

49. Artister med personer
@Entity
class Artist {
@Entity
@Id class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var id : Int = _
var name : String = _
var firstname : String = _
var biography : String = _
var lastname : String = _
@Temporal(value = TemporalType.DATE)
}
var founded : Date = _
}
Artist
Person
name : String
*
biography : Text firstname : String
*
«enumeration»
Genre
Artist
name : String
Album mainGenre : Genre lastname : String
Rock 1
Pop
Classic
biography : Text
mainGenre : Genre
founded : Date
*
name : String
release : Date
rating : Option[Int]
founded : Date biography : Text
Blues
Rap
HipHop
Alternative
split : Option[Date]
*
1 split : Option[Date]
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

50. Artister med personer
@Entity
class Artist {
@Entity
@Id class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var id : Int = _
var name : String = _
var firstname : String = _
var biography : String = _
var lastname : String = _
@Temporal(value = TemporalType.DATE)
}
var founded : Date = _
}
@ManyToMany
@JoinTable(name = "person_artist",
joinColumns = Array(new JoinColumn(name = "artist_id")),
inverseJoinColumns = Array(new JoinColumn(name = "person_id")))
var persons : jList[Person] = _
Artist
Person
name : String
*
biography : Text firstname : String
*
«enumeration»
Genre
Artist
name : String
Album mainGenre : Genre lastname : String
Rock 1
Pop
Classic
biography : Text
mainGenre : Genre
founded : Date
*
name : String
release : Date
rating : Option[Int]
founded : Date biography : Text
Blues
Rap
HipHop
Alternative
split : Option[Date]
*
1 split : Option[Date]
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

51. Artister med personer
@Entity
class Artist {
@Entity
@Id class Person {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
var id : Int = _
var name : String = _
var firstname : String = _
var biography : String = _
var lastname : String = _
@Temporal(value = TemporalType.DATE)
}
var founded : Date = _
}
@ManyToMany
@JoinTable(name = "person_artist",
@ManyToMany(mappedBy = "persons")
joinColumns = Array(new JoinColumn(name = "artist_id")),
inverseJoinColumns = Array(new JoinColumn(name = "person_id"))) var artists : jList[Artist] = _
var persons : jList[Person] = _
Artist
Person
name : String
*
biography : Text firstname : String
*
«enumeration»
Genre
Artist
name : String
Album mainGenre : Genre lastname : String
Rock 1
Pop
Classic
biography : Text
mainGenre : Genre
founded : Date
*
name : String
release : Date
rating : Option[Int]
founded : Date biography : Text
Blues
Rap
HipHop
Alternative
split : Option[Date]
*
1 split : Option[Date]
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

52. Opplevelsen så langt
• java collections
• ikkeno Option‐støtte
• Plagsom Enum
• Mer klønete bruk av annoteringer
© Mesan AS

53. Opplevelsen så langt
• java collections
• ikkeno Option‐støtte
• Plagsom Enum
• Mer klønete bruk av annoteringer
• Føles ikke veldig “Scalash”
© Mesan AS

54. Opplevelsen så langt
• java collections
• ikkeno Option‐støtte
• Plagsom Enum
• Mer klønete bruk av annoteringer
• Føles ikke veldig “Scalash”
• Javel, men vi prøver videre og bruker entitetene...
© Mesan AS

55. Insert
def createArtist(em:EntityManager) {
val a = new Artist
a.name = "Pink Floyd"
a.biography = "bla bla bla"
a.founded = "1965-01-20"
a.maingenre = Genre.Alternative
em.persist(a)
}
© Mesan AS

56. Insert
def createAlbum(em:EntityManager) {
def createArtist(em:EntityManager) {
val tool = em.find(classOf[Artist], 1001)
val a = new Artist
a.name = "Pink Floyd"
val album = new Album
a.biography = "bla bla bla"
album.name = "New one"
a.founded = "1965-01-20"
album.release = new Date()
a.maingenre = Genre.Alternative
album.rating = 5
em.persist(a)
tool.albums.add(album)
}
}
© Mesan AS

57. Selects
def findArtist(em:EntityManager) = {
val tool:Artist = em.find(classOf[Artist], 1001)
tool
}
def findArtistByName(em:EntityManager) = {
val q = em.createQuery("SELECT a FROM Artist a WHERE a.name = :name", classOf[Artist])
q.setParameter("name", "Tool")
val artist = q.getSingleResult
artist
}
def countArtists(em:EntityManager) = {
val q = em.createQuery("SELECT COUNT(a) FROM Artist a", classOf[Long])
val artistCount = q.getSingleResult
artistCount
}
def findArtists(em:EntityManager) = {
val q = em.createQuery("SELECT a FROM Artist a WHERE size(a.albums) > 4", classOf[Artist])
q.getResultList
}
© Mesan AS

58. Update
def updateRating(em:EntityManager) {
val tool = em.find(classOf[Artist], 1001)
def updateArtist(em:EntityManager) {
for (i <- 0 until tool.albums.size) {
val tool = em.find(classOf[Artist], 1001)
val album = tool.albums.get(0)
tool.name = "Updated..."
album.rating = 5
}
}
}
def updateRatingByQuery(em:EntityManager) {
val q = em.createQuery("""
UPDATE Album a SET rating = 5 WHERE a.id in
(SELECT album.id FROM Artist art JOIN art.albums album
WHERE art.id = :id)
""")
q.setParameter("id", 1001)
val up = q.executeUpdate() // up => 4
}
© Mesan AS

59. Hva kan vi forbedre?
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

60. Hva kan vi forbedre?
trait WithID {
• Traits FTW! @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
}
@Entity
class Song extends WithID {
var name : String = _
var duration : Int = _
var tracknumber : Int = _
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

61. Hva kan vi forbedre?
trait WithID {
• Traits FTW! @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
var id : Int = _
}
@Entity
class Song extends WithID {
var name : String = _
var duration : Int = _
var tracknumber : Int = _
}
class Album extends WithID {
var songs : jList[Song] = _
• Scala Collections def duration : Int = {
import scala.collection.JavaConversions._
songs.foldLeft(0)(_ + _.duration)
}
}
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

62. ScalaEntityManager
• Wrapper rundt EntityManager
• I samme stil som RichInt, StringOps etc
© Mesan AS

63. ScalaEntityManager
• Wrapper rundt EntityManager
• I samme stil som RichInt, StringOps etc
public interface EntityManager {
public <T> T find(Class<T> entityClass, Object primaryKey);
public Query createQuery(String qlString); trait ScalaEntityManager {
public <T> TypedQuery<T> createQuery(String qlString, def find[A](clazz: Class[A], id: Any) : Option[A]
Class<T> resultClass); def def createQuery[A](queryString: String) : ScalaQuery[A]
} }
public interface Query { class ScalaQuery[A] {
public List getResultList(); def findAll : Seq[A]
Object getSingleResult(); def getResultList() : Seq[A]
Query setParameter(String name, Object value); def findOne : Option[A]
} def setParams(params : Pair[String,Any]*)
public interface TypedQuery<X> extends Query { }
X getSingleResult();
java.util.List<X> getResultList();
}
© Mesan AS

64. Deler av veien, men...
© Mesan AS

65. Deler av veien, men...
• Føler at noe ikke stemmer her
© Mesan AS

66. Deler av veien, men...
• Føler at noe ikke stemmer her
• Får ikke utnyttet mulighetene i språket
© Mesan AS

67. Deler av veien, men...
• Føler at noe ikke stemmer her
• Får ikke utnyttet mulighetene i språket
• Hvorfor bruke Scala i det hele tatt?
© Mesan AS

68. Uklarheter
• Tung mental modell
Id Name Location
• Object Relational Impedence Mismatch
1 Mesan Oslo
2 NTNU Trondheim
3 NITH Oslo
Company
name : String 4 NFR Oslo
location : String
5 Sintef Trondheim
• Transaksjoner *
Person
firstname : String
lastname : String
Id
1
Firstname
John
Lastname
Doe
Company
1
2 Jane Doe 1
3 Peter Peterson 2
• Hva endres? Når skrives det til base?
4 Marky Mark 3
5 John Johnson 2
• Database‐struktur styrt av JPA?
• Skjønner man datamodellen? Eller må man lese JPA‐
koden for å henge med?
• Velge “eiende” side i relasjoner
© Mesan AS

69. • Trainwrecks / lasting av “hele” basen
• Traversering av objektmodell
vs Forretningsprosesser
• Uthenting av små datasett V1 V2 V3 V4 V5 V6 V7 V8 V9
F1 F2 F3 F4 F5 F6 F7
Artist
Album
name : String
1
biography : Text name : String
mainGenre : Genre
*
release : Date T1 T2 T3 T4 T5 T6
founded : Date rating : Option[Int]
split : Option[Date]
1
*
*
* Song
DB
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

70. Alternativer
© Mesan AS

71. JDBC
Rykk tilbake til start!
Ingen hindringer, ingen begrensinger
All makt
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

72. JDBC
• Direkte integrasjon mot databasen
• Ingen avhengigheter, fundamentalt i Java SE
• Grunnlaget for alle abstraksjoner
© Mesan AS

73. Modell
• Frie tøyler!
import Genre._
class Artist(val name: String, val biography: String,
val founded: Date, val split: Option[Date],
val mainGenre: Genre, val albums: List[Album] = Nil, val persons: List[Person] = Nil)
class Album(val name: String, val release: Date, val rating: Int,
val songs: List[Song] = Nil)
class Song(val name: String, val duration: Int, val tracknumber: Int)
class Person(val firstname: String, val lastname: String,
val biography: String)
«enumeration»
Artist
Genre Album
name : String
Rock 1
biography : Text name : String
Pop *
Classic mainGenre : Genre release : Date
Blues founded : Date rating : Option[Int]
Rap split : Option[Date]
1
HipHop
Alternative *
*
* Song
name : String
Person duration : Int
firstname : String trackNumber : Int
lastname : String
biography : Text
© Mesan AS

74. Insert
def con: Connection
def insertArtist {
val in = "INSERT INTO ARTISTS(name, biography, founded, maingenre) VALUES (?,?,?,?)"
val ps = con.prepareStatement(in)
ps.setString(1, "Tool")
ps.setString(2, "bla bla bla...")
ps.setDate(3, Date.valueOf("1990-01-02"))
ps.setInt(4, Genre.Rock.id)
ps.executeUpdate()
}
Artist
name : String
biography : Text
mainGenre : Genre
founded : Date
split : Option[Date]
© Mesan AS

75. Insert
def con: Connection
def insertArtist {
val in = "INSERT INTO ARTISTS(name, biography, founded, maingenre) VALUES (?,?,?,?)"
val ps = con.prepareStatement(in)
ps.setString(1, "Tool")
ps.setString(2, "bla bla bla...")
ps.setDate(3, Date.valueOf("1990-01-02"))
ps.setInt(4, Genre.Rock.id)
ps.executeUpdate()
}
def insertAlbum {
val in = "INSERT INTO ALBUMS(name, release, rating, artist_id) VALUES (?,?,?,?)"
val ps = con.prepareStatement(in)
ps.setString(1, "New one")
ps.setDate(2, Date.valueOf("2011-09-07"))
ps.setInt(3, 3)
ps.setInt(4, 1001)
Artist
ps.executeUpdate() name : String
} biography : Text
mainGenre : Genre
founded : Date
split : Option[Date]
© Mesan AS

76. Update
def updateArtist {
val ps = con.prepareStatement("UPDATE ARTISTS SET name = ? WHERE id = ?")
ps.setString(1, "updated...")
ps.setInt(2, 1001)
ps.executeUpdate()
}
Artist
name : String
biography : Text
mainGenre : Genre
founded : Date
split : Option[Date]
© Mesan AS

77. Update
def updateArtist {
val ps = con.prepareStatement("UPDATE ARTISTS SET name = ? WHERE id = ?")
ps.setString(1, "updated...")
ps.setInt(2, 1001)
ps.executeUpdate()
}
def updateAlbums {
val ps = con.prepareStatement("UPDATE ALBUMS SET rating = ? WHERE artist_id = ?")
ps.setInt(1, 5)
ps.setInt(2, 1001)
ps.executeUpdate()
}
Artist
name : String
biography : Text
mainGenre : Genre
founded : Date
split : Option[Date]
© Mesan AS

78. Finn én (eller ingen)
def findArtist : Option[Artist] = {
st = conn.prepareStatement(
"SELECT id, name, biography, founded, split, maingenre FROM ARTISTS WHERE id=?")
st.setInt(1, 1001)
rs = st.executeQuery()
if (rs.next()) {
val id = rs.getInt(1)
val name = rs.getString(2)
val bio = rs.getString(3)
val founded = rs.getDate(4)
val split = rs.getDate(5)
val splitO = if (split != null) Some(split) else None
val gen = Genre(rs.getInt(6))
Some(new Artist(name, bio, founded, splitO, gen))
} else {
None
}
}
© Mesan AS

79. Finn mange
def findAllArtists : List[Artist] = {
var res = List[Artist]()
val st = con.prepareStatement(
"SELECT id, name, biography, founded, split, maingenre FROM ARTISTS")
val rs = st.executeQuery()
while (rs.next()) {
val name = rs.getString(2)
val bio = rs.getString(3)
val founded = rs.getDate(4)
val split = rs.getDate(5)
val splitO = if (split != null) Some(split) else None
val gen = Genre(rs.getInt(6))
val a = new Artist(name, bio, founded, splitO, gen)
res ::= a
}
res.reverse
}
© Mesan AS

80. Finn album med sanger
def findAlbum() = {
val q =
"
SELECT a.id, a.name, a.release, a.rating, s.name, s.duration, s.tracknumber
FROM Albums a JOIN Songs s ON s.album_id = a.id
WHERE a.id = ?
ORDER BY s.tracknumber ASC
"
val ps = con.prepareStatement(q)
ps.setInt(1, 1001)
val rs = ps.executeQuery()
while (rs.next) {
// extract song, add to list
val s = new Song(name, duration, tracknumber)
songs ::= a
}
// extract album from last row, add songs to artist
new Album(name, release, rating, songs)
}
© Mesan AS

81. Oppsiden
• Full kontroll på all SQL
• Hvilken SQL som kjøres
• Når den kjøres
• Full valgfrihet i modellering av data
• class, case class, Option[] etc
• Tilgang til alt vi ønsker oss
© Mesan AS

82. What´s the catch?
© Mesan AS

83. What´s the catch?
• boilerplate
© Mesan AS

84. What´s the catch?
var conn : Connection = null
• boilerplate var st : PreparedStatement = null
try {
conn = con
st = conn.prepareStatement("SQL here")
// do something SQLy
} finally {
st.close()
conn.close()
if (rs.next()) {
}
// do something with resultset
} st.setInt(1, 1)
while (rs.next()) { st.setXXX
// do something with resultset
} rs.getInt(1)
rs.getString(2)
rs.getXxx(3)
© Mesan AS

85. What´s the catch?
var conn : Connection = null
• boilerplate var st : PreparedStatement = null
try {
conn = con
st = conn.prepareStatement("SQL here")
// do something SQLy
} finally {
st.close()
conn.close()
if (rs.next()) {
}
// do something with resultset
} st.setInt(1, 1)
while (rs.next()) { st.setXXX
// do something with resultset
} rs.getInt(1)
rs.getString(2)
rs.getXxx(3)
• Lock‐in mot database‐leverandør
• Lav‐nivå API å forholde seg til
• Håndkoding av all SQL
© Mesan AS

86. RichSQL
Kan det fikses?
Klart det kan!
© Mesan AS