Hello r2dbc with Kotlin - mike-neckのブログ

リアクティブな感じで RDB に接続できるやつ。内容的にはバファさんのブログの下位互換未満。

bufferings.hatenablog.com

準備1

使ったデータベースは postgres で、docker で用意した。とりあえず、こんな感じのテーブルを作っておく。

create table users(
  id bigint not null primary key ,
  name varchar(31) not null unique ,
  created timestamp not null 
);

ついでにデータを入れておく

insert into users (id, name, created)
values (1, 'test-user', '2019-01-01 10:00:00'),
       (2, 'test-admin', '2019-01-15 10:00:00'),
       (3, 'test-owner', '2019-02-01 10:00:00'),
       (4, 'test-guest', '2019-02-15 10:00:00');

準備2

gradle は次のような感じ(Kotlin)

import java.net.URI

plugins {
    id("org.jetbrains.kotlin.jvm").version("1.3.20")
}

repositories {
    jcenter()
    mavenCentral()
    maven {
        url = URI.create("https://repo.spring.io/libs-milestone/")
    }
}
dependencies {
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-reactor:1.1.1")

    implementation("io.projectreactor:reactor-core:3.2.6.RELEASE")
    implementation(group = "io.r2dbc", name = "r2dbc-postgresql", version = "1.0.0.M7")

    testImplementation("org.junit.jupiter:junit-jupiter:5.4.0")
    testImplementation("org.jetbrains.kotlin:kotlin-test-junit5:1.3.21")
    testImplementation("io.projectreactor:reactor-test:3.2.6.RELEASE")
}

ちょっと動かす

テストデータは入っているので、クエリーを投げるところです

@Test
fun noKoroutine() {
  val options = ConnectionFactoryOptions.builder()
      .option(ConnectionFactoryOptions.DRIVER, "postgresql")
      .option(ConnectionFactoryOptions.HOST, "localhost")
      .option(ConnectionFactoryOptions.PORT, 5432)
      .option(ConnectionFactoryOptions.USER, "postgres-user")
      .option(ConnectionFactoryOptions.PASSWORD, "postgres-pass")
      .option(ConnectionFactoryOptions.DATABASE, "postgres")
      .build()
  val connectionFactory: ConnectionFactory = ConnectionFactories.get(options)
  val conn = Mono.from(connectionFactory.create())
  val users = conn.flatMapMany { connection ->
    connection.createStatement(
        //language=SQL
        "SELECT u.id, u.name, u.created FROM users AS u WHERE u.name = $1")
        .bind("$1", "test-user")
        .execute() }
      .flatMap { result ->
        result.map { row, meta ->
          val name = row.get("name", String::class.javaObjectType)
          val id = row.get("id", Long::class.javaObjectType)
          val created = row.get("created", Instant::class.java)
          return@map if (created != null && name != null && id != null) User(id, name, created)
          else null
        }
      }
      .filter { it != null }
      .cast(User::class.java)
  runBlocking {
    users.buffer().consumeEach {
      println(it)
    }
  }
}

実行結果

f:id:mike_neck:20190317201815p:plain

番外編

Kotlin-Coroutine を使うといい感じのコードになるのかと思ったけど、

// GlobalScope.flux 内
val result = connection.createStatement(
        //language=SQL
        "SELECT u.id, u.name, u.created FROM users AS u WHERE u.name = $1")
        .bind("$1", "test-user")
        .execute()
        .awaitSingle()

result.map { row, _ ->
    val name = row.get("name", String::class.javaObjectType)
    val id = row.get("id", Long::class.javaObjectType)
    val created = row.get("created", Instant::class.java)
    return@map if (created != null && name != null && id != null) User(id, name, created)
    else null
}.consumeEach { if (it != null) channel.offer(it) }