「Server-Side Kotlin Study #1」の発表資料です https://server-sider-kotlin.connpass.com/event/210853/

1. 100%KotlinのORM
Ktormを試してみた
（Exposedとの⽐較アリ）
Server-Side Kotlin Study #1
2021/05/12
1

2. ⾃⼰紹介
塚本啓太
株式会社イエソドエンジニア
KotlinとTypeScriptが⼤好きだけど、
たまにvalとconstを間違える。
Twitter: @tsukakei1012
GitHub: tsukakei
2

3. 会社紹介
株式会社イエソド
SaaS統制プラットフォーム
『YESOD』
⼈・組織・情報と
SaaSをシームレスに
管理するためのSaaS
https://www.yesod.co/
KotlinとTypeScriptで
できています 3

4. 今⽇話すこと
Ktormの紹介
Exposedとの⽐較
4

5. とは
100%Kotlinの軽量ORM
ConfigファイルもXMLもサードパーティ依存もなく軽量で使いやす
い
強く型付けされたSQL DSL
柔軟なクエリ、適度な粒度で思った通りのSQLが書ける
filter や map のようなKotlin nativeの感覚で書けるAPIを提供
拡張可能なデザイン
https://www.ktorm.org/
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6. あれ、でもExposedは？？
6

7. とは
JetBrains製の100% Kotlin ORM
JetBrains製という絶対正義感
アイコンは
Ktorm同様に軽量さと型付けを特徴としている
https://github.com/JetBrains/Exposed
Google TrendsではExposedの圧勝
https://kotlin.libhunt.com/compare-exposed-vs-ktorm
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8. せっかくなので⽐較してみましょう
レポジトリを⽤意しました
https://github.com/tsukakei/KotlinOrmSample
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9. ダウンロード⽅法
Ktorm
implementation("org.ktorm:ktorm-core:3.3.0")
Exposed
implementation("org.jetbrains.exposed", "exposed-core", "0.31.1")
implementation("org.jetbrains.exposed", "exposed-dao", "0.31.1")
implementation("org.jetbrains.exposed", "exposed-jdbc", "0.31.1")
implementation("org.jetbrains.exposed", "exposed-jodatime", "0.31.1")
implementation("mysql", "mysql-connector-java", "8.0.24")
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10. DBへの接続とトランザクション
DBへの接続(基本項⽬はほぼ同じ、オプションが異なる)
// ktrom
val database = Database.connect("jdbc:mysql://localhost:3306/sample_db", user = "root", password = "root")
// exposed
val database = Database.connect("jdbc:mysql://localhost:3306/sample_db", user = "root", password = "root")
トランザクション
// ktrom
database.useTransaction { }
// exposed
transaction(database) { }
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11. DSLの⽐較
テーブル定義
各種SQL
SELECT
AGGREGATION, UNION, JOIN
INSERT, UPDATE, DELETE
レポジトリ
https://github.com/tsukakei/KotlinOrmSample
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12. テーブル定義（SQL）
CREATE TABLE t_department(
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(128) NOT NULL,
location VARCHAR(128) NOT NULL
);
CREATE TABLE t_employee(
id INT NOT NULL PRIMARY KEY AUTO_INCREMENT,
name VARCHAR(128) NOT NULL,
job VARCHAR(128) NOT NULL,
hire_date DATE NOT NULL,
salary BIGINT NOT NULL,
department_id INT NOT NULL
);
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13. テーブル定義（Ktorm）
object KtormDepartments : Table<Department>("t_department") {
val id = int("id").primaryKey().bindTo { it.id }
val name = varchar("name").bindTo { it.name }
val location = varchar("location").bindTo { it.location }
}
object KtormEmployees : Table<Employee>("t_employee") {
val id = int("id").primaryKey().bindTo { it.id }
val name = varchar("name").bindTo { it.name }
val job = varchar("job").bindTo { it.job }
val hireDate = date("hire_date").bindTo { it.hireDate }
val salary = long("salary").bindTo { it.salary }
val departmentId = int("department_id").references(KtormDepartments) { it.department }
}
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14. テーブル定義（Exposed）
object ExposedDepartments : IntIdTable("t_department") {
val name = varchar("name", 50)
val location = varchar("location", 50)
}
object ExposedEmployees : IntIdTable("t_employee") {
val name = varchar("name", 50)
val job = varchar("job", 50).nullable()
val hireDate = date("hire_date")
val salary = long("salary")
val departmentId = reference("department_id", ExposedDepartments.id)
}
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15. SELECT
// Ktorm
database
.from(KtormEmployees)
.select(KtormEmployees.name)
.where { (KtormEmployees.departmentId notEq 4) and (KtormEmployees.name like "%郎%") }
// Exposed
ExposedEmployees
.slice(ExposedEmployees.name)
.select { (ExposedEmployees.departmentId eq 1) and (ExposedEmployees.name like "%郎%") }
SQL: SELECT t_employee.`name` FROM t_employee WHERE (t_employee.department_id = 1) AND (t_employee.`name` LIKE '%郎%')
Ktorm: SQLそのまんま
Exposed: selectにwhere式を渡す& sliceで取得したい列を指定 15

16. AGGREGATION
// Ktorm
database.from(KtormEmployees)
.select(KtormEmployees.departmentId, avg(KtormEmployees.salary))
.groupBy(KtormEmployees.departmentId)
.having { avg(KtormEmployees.salary) greater 100.0 }
// Exposed
ExposedEmployees
.slice(ExposedEmployees.departmentId, ExposedEmployees.salary.avg())
.selectAll()
.groupBy(ExposedEmployees.departmentId)
.having { ExposedEmployees.salary.avg() greater 100.0 }
SQL: SELECT t_employee.department_id, AVG(t_employee.salary) FROM t_employee
GROUP BY t_employee.department_id HAVING AVG(t_employee.salary) > 100.0 16

17. UNION
// Ktorm
database
.from(KtormEmployees)
.select(KtormEmployees.id)
.unionAll(database.from(KtormDepartments).select(KtormDepartments.id))
// Exposed
ExposedEmployees
.slice(ExposedEmployees.id)
.selectAll()
.union(ExposedDepartments.slice(ExposedDepartments.id).selectAll())
SQL: SELECT t_employee.id FROM t_employee UNION SELECT t_department.id FROM t_department
17

18. JOIN
// Ktorm
database
.from(KtormEmployees)
.leftJoin(KtormDepartments, on = KtormEmployees.departmentId eq KtormDepartments.id)
.select(KtormEmployees.name, KtormDepartments.name)
.orderBy(KtormEmployees.id.asc())
// Exposed
ExposedEmployees
.join(ExposedDepartments, JoinType.LEFT)
.slice(ExposedEmployees.name, ExposedDepartments.name)
.selectAll()
.orderBy(ExposedEmployees.id to SortOrder.ASC)
SQL: SELECT t_employee.`name`, t_department.`name` FROM t_employee
LEFT JOIN t_department ON t_department.id = t_employee.department_id ORDER BY t_employee.id ASC
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19. INSERT
database.insert(KtormEmployees) {
set(it.name, "Server-side 三郎")
set(it.job, "Fullstack")
set(it.hireDate, LocalDate.now())
set(it.salary, 10000)
set(it.departmentId, 1)
}
ExposedEmployees.insert {
it[name] = "Server-side 三郎"
it[job] = "Fullstack Engineer"
it[hireDate] = DateTime.now()
it[salary] = 10000
it[departmentId] = 1
}
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20. UPDATE & DELETE
// Ktorm
database.update(KtormEmployees) {
set(it.salary, 100)
where { it.id eq 2 }
}
database.delete(KtormEmployees) { it.id eq 4 }
// Exposed
ExposedEmployees.update({ ExposedEmployees.id eq 2 }) {
it[salary] = 100
}
ExposedEmployees.deleteWhere { ExposedEmployees.id eq 4 }
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21. DSLまとめ
KtormもExposedもメソッドチェイニングでスルスルと書ける
Ktormの⽅がよりSQLライク
Exposedはやりたいことをしたいときにドキュメントを読む必要が
あるように感じた
21

22. DAO
Entity定義
CRUD
レポジトリ
https://github.com/tsukakei/KotlinOrmSample
22

23. Entity定義（Ktorm）
interface Department : Entity<Department> {
companion object : Entity.Factory<Department>()
val id: Int
var name: String
var location: String
}
interface Employee : Entity<Employee> {
companion object : Entity.Factory<Employee>()
val id: Int
var name: String
var job: String
var hireDate: LocalDate
var salary: Long
var department: Department
}
23

24. Entity定義（Exposed）
class ExposedDepartment(id: EntityID<Int>) : IntEntity(id) {
companion object : IntEntityClass<ExposedDepartment>(ExposedDepartments)
var name by ExposedDepartments.name
var location by ExposedDepartments.location
}
class ExposedEmployee(id: EntityID<Int>) : IntEntity(id) {
companion object : IntEntityClass<ExposedEmployee>(ExposedEmployees)
var name by ExposedEmployees.name
var job by ExposedEmployees.job
var hireDate by ExposedEmployees.hireDate
var salary by ExposedEmployees.salary
var department by ExposedDepartment referencedOn ExposedEmployees.departmentId
}
24

25. CRUD (Ktorm)
// create
val department = Department {
name = "Sales"
location = "Osaka"
}
database.sequenceOf(KtormDepartments).add(department)
// update
department.run {
location = "Fukuoka"
flushChanges()
}
// read
database.sequenceOf(KtormDepartments).find { it.id eq department.id }?.also { println(it.location) }
// delete
department.delete()
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26. CRUD (Exposed)
// create
val department = ExposedDepartment.new {
name = "Sales"
location = "Osaka"
}
// update
department.location = "Fukuoka"
// read
ExposedDepartment.findById(department.id)?.also { println(it.location) }
// delete
department.delete()
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27. DAOまとめ
Ktormは少しDatabaseを意識しないといけない
その分、少し冗⻑に感じた
TableとEntityの扱い⽅が微妙に違う
ExposedはTable定義が先、Entityが後
KtormはEntityが先、Tableが後
27

28. KtormとExposedの⽐較まとめ
基本的な機能や型サポートについては⼤差ないように感じた
互いにMySQL・PostgreSQL・Oracle・SQL Serverをサポート
書き⽅やドキュメントについてはKtormの⽅が好み
しかしながら、JetBrains開発という安⼼感がExposedにはある
Exposed Ktorm
開発元 JetBrains 個⼈開発者(@vincentlauvlwj)
数 5.1K 1K弱
採⽤実績 YESOD, UPSIDER 皆無？ 28

29. We're hiring!
モダンな静的型付け⾔語で
B2B SaaSを開発したい
エンジニア募集！
https://www.wantedly.com/pr
ojects/631289
Kotlin (Ktor + Exposed)
使ってます！！
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