KotlinでDBアクセス

gistfile1.kt

// 原始的でシンプルな方法

package com.taroid.sample

import java.sql.DriverManager
import java.sql.ResultSet
import java.sql.Statement
import java.sql.Connection

fun main(args: Array<String>) {
    val articles = findAllArticles()
    println(articles)
}

fun findAllArticles(): List<Article> {
    var conn: Connection? = null
    var statement: Statement? = null
    var resultSet: ResultSet? = null

    val articleListBuilder = ImmutableArrayListBuilder<Article>()

    try {
        conn = DriverManager.getConnection("jdbc:postgresql://localhost/sample")
        statement = conn?.createStatement()
        resultSet = statement?.executeQuery("select * from articles")
        while(resultSet?.next() ?: false) {
            articleListBuilder.add(Article(
                    resultSet!!.getLong(1),
                    resultSet!!.getString(2)!!,
                    resultSet!!.getString(3) ?: "",
                    resultSet!!.getString(4)!!
            ))
        }
    } finally {
        resultSet?.close()
        statement?.close()
        conn?.close()
    }

    return articleListBuilder.build()
}

data class Article(
        val id: Long,
        val title: String,
        val author: String,
        val content: String
)

gistfile2.kt

// kotlin.jdbcライブラリを使った方法

package com.taroid.sample

import kotlin.jdbc.getConnection
import kotlin.jdbc.use
import kotlin.jdbc.useSql
import kotlin.jdbc.iterator

fun main(args: Array<String>) {
    val articles = findAllArticles()
    println(articles)
}

fun findAllArticles(): List<Article> {
    val articleListBuilder = ImmutableArrayListBuilder<Article>()

    getConnection("jdbc:postgresql://localhost/sample").use {

        // useSql -> use にリネーム予定
        it.createStatement()?.useSql {
            it.executeQuery("select * from articles").use {
                it.iterator().forEach {
                    articleListBuilder.add(Article(
                        it.getLong(1),
                        it.getString(2)!!,
                        it.getString(3) ?: "",
                        it.getString(4)!!
                    ))
                }
            }
        }
    }

    return articleListBuilder.build()
}

data class Article(
        val id: Long,
        val title: String,
        val author: String,
        val content: String
)