IntelliJ: Java 標準ライブラリーで HTTP リクエスト

次のサンプルの
Java 標準ライブラリの API を使用して Kotlin で HTTP リクエストを作成する
と同じことを行いました。
Kotlin で HTTP リクエストを作成する

サーバー仕様

次のようにして、JSON が GET で取得できるとします。

http https://ekzemplaro.org/tmp/country_all.json

取得できる JSON

country_all.json

[{"id":18,"countryName":"Kenya"},
{"id":20,"countryName":"Tanzania"},
{"id":21,"countryName":"Ethiopia"},
{"id":22,"countryName":"Malawi"},
{"id":23,"countryName":"Country"},
{"id":24,"countryName":"Country"},
{"id":25,"countryName":"Kenya"},
{"id":26,"countryName":"Country"},
{"id":27,"countryName":"USA"},
{"id":28,"countryName":"USA"},
{"id":29,"countryName":"Kenya"},
{"id":30,"countryName":"Kenya"}]

プログラム

Main.kt

import java.net.HttpURLConnection
import java.net.URI

fun main(){

    val url_string = "https://ekzemplaro.org/tmp/country_all.json"
    val uri =  URI(url_string)
    val url = uri.toURL()
    val con = url.openConnection() as HttpURLConnection

    // 接続設定(ミリ秒で指定)
    con.connectTimeout = 20_000 // 20 秒
    con.readTimeout = 20_000    // 20 秒
    con.requestMethod = "GET"   // GETの場合は省略可能

    // 接続を確立
    con.connect()

    // レスポンスを取得
    val str = con.inputStream.bufferedReader(Charsets.UTF_8).use { br ->
        br.readLines().joinToString("")
    }

    // 表示
    println(str)
}

実行結果

/usr/lib/jvm/java-1.21.0-openjdk-amd64/bin/java -javaagent:/snap/intellij-idea-community/464/lib/idea_rt.jar=36781:/snap/intellij-idea-community/464/bin -Dfile.encoding=UTF-8 -Dsun.stdout.encoding=UTF-8 -Dsun.stderr.encoding=UTF-8 -classpath /home/uchida/IdeaProjects/get01/build/classes/kotlin/main:/home/uchida/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk8/1.9.0/e000bd084353d84c9e888f6fb341dc1f5b79d948/kotlin-stdlib-jdk8-1.9.0.jar:/home/uchida/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-jdk7/1.9.0/f320478990d05e0cfaadd74f9619fd6027adbf37/kotlin-stdlib-jdk7-1.9.0.jar:/home/uchida/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib/1.9.0/8ee15ef0c67dc83d874f412d84378d7f0eb50b63/kotlin-stdlib-1.9.0.jar:/home/uchida/.gradle/caches/modules-2/files-2.1/org.jetbrains.kotlin/kotlin-stdlib-common/1.9.0/cd65c21cfd1eec4d44ef09f9f52b6d9f8a720636/kotlin-stdlib-common-1.9.0.jar:/home/uchida/.gradle/caches/modules-2/files-2.1/org.jetbrains/annotations/13.0/919f0dfe192fb4e063e7dacadee7f8bb9a2672a9/annotations-13.0.jar MainKt
[{"id":18,"countryName":"Kenya"},{"id":20,"countryName":"Tanzania"},{"id":21,"countryName":"Ethiopia"},{"id":22,"countryName":"Malawi"},{"id":23,"countryName":"Country"},{"id":24,"countryName":"Country"},{"id":25,"countryName":"Kenya"},{"id":26,"countryName":"Country"},{"id":27,"countryName":"USA"},{"id":28,"countryName":"USA"},{"id":29,"countryName":"Kenya"},{"id":30,"countryName":"Kenya"}]

Process finished with exit code 0