Kotlin 网络编程

HTTP 请求

使用 HttpURLConnection

import java.net.HttpURLConnection
import java.net.URL

fun main() {
    val url = URL("https://api.example.com/data")
    val connection = url.openConnection() as HttpURLConnection
    
    connection.requestMethod = "GET"
    connection.setRequestProperty("Accept", "application/json")
    
    if (connection.responseCode == 200) {
        val response = connection.inputStream.bufferedReader().readText()
        println(response)
    }
    
    connection.disconnect()
}

使用 khttp 库

// build.gradle.kts
dependencies {
    implementation("khttp:khttp:0.1.0")
}

import khttp.get

fun main() {
    val response = get("https://api.example.com/users")
    println(response.statusCode)
    println(response.jsonObject)
}

使用 Fuel 库

// build.gradle.kts
dependencies {
    implementation("com.github.kittinunf.fuel:fuel:2.3.1")
}

import com.github.kittinunf.fuel.httpGet

fun main() {
    "https://api.example.com/users".httpGet().response { _, _, result ->
        val (data, _) = result
        println(String(data!!))
    }
}

JSON 解析

使用 Gson

// build.gradle.kts
dependencies {
    implementation("com.google.code.gson:gson:2.10.1")
}

import com.google.gson.Gson

data class User(val name: String, val age: Int)

fun main() {
    val gson = Gson()
    
    // JSON 转对象
    val json = """{"name": "Tom", "age": 25}"""
    val user = gson.fromJson(json, User::class.java)
    
    // 对象转 JSON
    val newJson = gson.toJson(User("Jerry", 30))
    println(newJson)
}

使用 kotlinx.serialization

// build.gradle.kts
plugins {
    kotlin("jvm") version "1.9.22"
    kotlin("plugin.serialization") version "1.9.22"
}

dependencies {
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-json:1.6.2")
}

import kotlinx.serialization.*

@Serializable
data class User(val name: String, val age: Int)

fun main() {
    // JSON 转对象
    val user = Json.decodeFromString<User>("""{"name": "Tom", "age": 25}""")
    
    // 对象转 JSON
    val json = Json.encodeToString(User("Jerry", 30))
    println(json)
}

使用协程

import kotlinx.coroutines.*
import java.net.HttpURLConnection
import java.net.URL

suspend fun fetchData(url: String): String = withContext(Dispatchers.IO) {
    val connection = URL(url).openConnection() as HttpURLConnection
    try {
        connection.responseCode
        connection.inputStream.bufferedReader().readText()
    } finally {
        connection.disconnect()
    }
}

fun main() = runBlocking {
    val data = fetchData("https://api.example.com/data")
    println(data)
}