在這場工作坊裡，我們使用 Kotlin 以 Serverless 的方式撰寫一個 JSON API 服務，並部署到 GCP Cloud Functions 服務。本章為第三單元，帶著學員完成一個 Mock API，可以動態地回傳一定筆數的 JSON 資料。 詳細步驟可參考講義：http://bit.ly/ktsvless

1. (Shengyou Fan)
GDG Taichung
2021/04/17
Cloud Functions
Kotlin Serverless API
- Ch.3 JSON API -
Photo by Jean-Philippe Delberghe on Unsplash

2. —
• JSON Response
• Data Class
• JSON Serialization

3. —
?query=param
①
②
③
⑤
Client
FaaS
Local Development
Kotlin Functions
④

4. HTTP Request
—
GET http://localhost:8080/getfeed?limit={n}
Accept: application/json
GET http://localhost:8080/findfeed?id={id}
Accept: application/json
1. n
2. JSON
1. id
2. JSON

5. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
if ("GET" != request.method.toUpperCase()) {
with(response) {
setStatusCode(HttpURLConnection.HTTP_BAD_METHOD)
writer.write("Bad method")
}
return
}
}
}
HTTP Method
—

6. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
with(res) {
setStatusCode(HttpURLConnection.HTTP_OK)
setContentType("application/json")
writer.write("...JSON STING...")
}
}
}
JSON
—
• HTTP Status Code
• Content-Type
•

7. HTTP Response
—
{
"data": [
{
"id": ...,
"title": "...",
"author": "...",
"content": "...",
"coverUrl": "...",
"permalink": "...",
"publishedAt": "..."
},
// ...
]
}
1. n
2. JSON
3. data

8. Data Class
—
// Data Class
data class News(
val id: String,
val title: String,
val author: String,
val content: String,
val coverUrl: String?
val permalink: String,
val publishedAt: String,
)
// JSON
{
"id": 1,
"title": "...",
"author": "...",
"content": "...",
"coverUrl": "...",
"permalink": "...",
"publishedAt": “..."
}
• JSON Data Class

9. // build.gradle
plugins {
id("...kotlin.plugin.serialization") version "..."
}
dependencies {
implementation("...:kotlinx-serialization-json:$ver")
}
• Gradle Plugin
Serialization
—
•

10. // News
@Serializable
data class News(
// ...
)
Annotation
—

11. val news = (1..10).map { id ->
News(
// ...
)
}
—

12. Json.encodeToString(
mapOf("data" to news)
)
JSON
—
JSON
• List Map data
• Map JSON

13. class Handler: HttpFunction {
@Throws(IOException::class)
override fun service(req: HttpRequest, res: HttpResponse) {
val limit = request.queryParameters["limit"]?
.first()?
.toIntOrNull() ?: 10
}
}
Query
—
• HttpRequest Query
•

14. Java Faker
—
• Java Faker
// build.gradle
dependencies {
implementation("com.github.javafaker:javafaker:$ver")
}

15. val faker = Faker.instance(Locale.TRADITIONAL_CHINESE)
News(
id = ...,
title = faker.lorem().sentence(),
author = faker.name().fullName(),
content = faker.lorem().paragraph(),
coverUrl = "https://${faker.internet().url()}",
permalink = "https://${faker.internet().url()}",
publishedAt = ...,
)
—
• Faker