受邀至 Kotlin Night Taipei 分享如何以 Ktor 這套 100% 用 Kotlin 打造的框架快速開發 Web 應用，包括網頁及 API 兩種方式，以及如何整合 Exposed SQL Library 做出 CRUD 各種功能。

1. Ktor
Web
—
(Shengyou Fan)
Kotlin Night Taipei
2019/12/13

2. —
• Developer Advocate
• Backend Developer
• Open Source Community Organizer

3. Kotlin https://youtu.be/hg8oYJ8Ez8s
• General-purpose
• Static typing
• OOP + FP
• Developed by
JetBrains
• Open Source
(Apache 2.0)
https://kotlinlang.org/
Kotlin
—

4. Kotlin
—
Browser
Kotlin/JS
Server
Kotlin/JVM
iOS
Kotlin/Native
Android
Kotlin/JVM

5. Kotlin Web
—
Server
Database
Client
Kotlin/JVM

6. Ktor
—
https://ktor.io/
• Web Framework
• Asynchronous
• Servers + Clients
• Developed by
JetBrains
• Open Source
(Apache 2.0)

7. Ktor Application
—
Client
Ktor App
HTTP Server
Feature
Feature
Feature

8. Routing
—
routing {
}

9. HTTP Method
—
routing {
get("/") {
}
}

10. Call
—
routing {
get("/") {
call.
}
}

11. Hello, world
—
routing {
get("/") {
call.respondText("Hello, world")
}
}

12. —
routing {
get("/") {
call.respondText(
"Hello, world",
ContentType.Text.Plain,
HttpStatusCode.OK
)
}
}

13. HTML respond
—
install(FreeMarker) {
templateLoader = ClassTemplateLoader(
this::class.java.classLoader,
"templates"
)
}
get("/") {
// ...
call.respond(
FreeMarkerContent(
"*.ftl",
mapOf("..." to ...)
)
)
}

14. JSON respond
—
install(ContentNegotiation) {
jackson {
}
}
get("/api/v1/books") {
val book = BookRespond("...")
call.respond(
mapOf("book" to book)
)
}
data class BookRespond (
val title: String,
val isbn: String,
)

15. Exposed
—
// gradle.properties
exposed_version=0.17.7
mysql_connector_version=5.1.46
// build.gradle
dependencies {
//...
implementation "org.jetbrains.exposed:exposed:$ver"
implementation "mysql:mysql-connector-java:$ver"
}

16. MySQL
—
version: "2"
services:
database:
image: mysql:5.7
ports:
- "...:3306"
environment:
MYSQL_ROOT_PASSWORD: ...
MYSQL_DATABASE: ...
command: ...

17. —
object Books : Table() {
val id: Column<Int> = integer("id")
.autoIncrement()
.primaryKey()
val title: Column<String> = varchar("title", 255)
val isbn: Column<String> = varchar("isbn", 13)
val publishedAt: Column<DateTime> = datetime("...")
}
object Books : IntIdTable() {
val title = varchar("title", 255)
val isbn = varchar("isbn", 13)
val publishedAt = datetime("...")
}

18. DAO
—
class Book(id: EntityID<Int>) : IntEntity(id) {
companion object : IntEntityClass<Book>(Books)
var title by Books.title
var isbn by Books.isbn
var publishedAt by Books.publishedAt
}

19. —
Database.connect(
url = "...",
driver = "com.mysql.jdbc.Driver",
user = "...",
password = "..."
)

20. —
transaction {
// ...
SchemaUtils.drop(…)
// ...
SchemaUtils.create(...)
}

21. // create
Book.new {
title = ...
}
// read
Book.all()
Book.find { ... }
.sortedBy { it.id }
// update
val book = Book.findById(...)
if (book != null) {
book.title = ...
}
// delete
val book = Book.findById(1)
book?.delete()
CRUD (DAO)
—

22. —
• Ktor
• Application Call Request & Response
• Routing
• Template (HTML)
• API (JSON)
• Exposed DB

23. —
Talking Kotlin http://talkingkotlin.com/ktor-with-ryan-harter/
FreeMarker https://freemarker.apache.org/docs/dgui_quickstart.htmlKtor https://ktor.io/servers/index.html
KotlinConf https://youtu.be/V4PS3IjIzlw

24. ktor.guide
Ktor
—

25. Web
(Shengyou)
shengyou.fan@jetbrains.com
Q&A
—
Ktor