How to setup SQLite in Kotlin? - sqlite

Question

I'm currently writing a chat application in Kotlin and want to implement authentication, by storing hashed passwords on my server in a database.
I don't have any experience with Databases, so I chose the most simple looking one I found after about 30 minutes of google search. SQLite.
Unfortunatly there isn't any real setup guide for SQLite in Kotlin.
Could someone please write a small step by step guide on how to :
install SQLite
connect to it
use it in source code(e.g. create a table with one or two values)
all in Kotlin if possible
I'm grateful for any help!

Answer 1

Here's an MWE using JDBC API on Ubuntu 20.04:
sudo apt install sqlite3
SQLITE_VERSION=`sqlite3 --version | cut -d ' ' -f 1` # 3.31.1 on Ubuntu 20.04
curl -s https://get.sdkman.io | bash
sdk i java # for JDBC
sdk i maven # for JDBC interface to SQLite (see later)
sdk i kotlin 1.4.10 # later versions are currently affected by:
# https://youtrack.jetbrains.com/issue/KT-43520
cat > demo.main.kts <<EOF
#!/usr/bin/env kotlin
# uses maven to install the dependency from maven central:
# reference: https://github.com/Kotlin/KEEP/blob/master/proposals/scripting-support.md#kotlin-main-kts
#file:DependsOn("org.xerial:sqlite-jdbc:$SQLITE_VERSION")
import java.sql.DriverManager
import java.sql.Connection
import java.sql.Statement
import java.sql.ResultSet
# creates or connects to database.sqlite3 file in the current directory:
var connection = DriverManager.getConnection("jdbc:sqlite:database.sqlite3")
var statement = connection.createStatement()
statement.executeUpdate("drop table if exists people")
statement.executeUpdate("create table people (id integer, name string)")
statement.executeUpdate("insert into people values(1, 'leo')")
statement.executeUpdate("insert into people values(2, 'yui')")
var resultSet = statement.executeQuery("select * from people")
while ( resultSet.next() ) {
println( "id = " + resultSet.getInt("id") )
println( "name = " + resultSet.getString("name") )
println()
}
connection.close()
EOF
chmod +x demo.main.kts
./demo.main.kts

Answer 2

Sqlite doesn't work with a client-server model. The datas are stored in file of your choice, so there is no installation to do.
Maybe you can look Exposed. It is a kotlin library for sql database (sqlite included).
There is a documentation here.
You just need to add the 'org.jetbrains.exposed:exposed' depedency to gradle or maven (+ the jdbc library depedency, for SQLlite it is 'org.xerial:sqlite-jdbc').

Answer 3

import com.sun.net.httpserver.HttpServer
import java.io.PrintWriter
import java.net.InetSocketAddress
import java.sql.* // Connection, DriverManager, SQLException
import java.util.Properties
/**
https://www.tutorialkart.com/kotlin/connect-to-mysql-database-from-kotlin-using-jdbc/
$ wget https://repo1.maven.org/maven2/org/xerial/sqlite-jdbc/3.27.2.1/sqlite-jdbc-3.27.2.1.jar
$ kotlinc sqws.kt; kotlin -cp ".:./sqlite-jdbc-3.27.2.1.jar" SqwsKt
Minimal embedded HTTP server in Kotlin using Java built in HttpServer
**/
fun main(args: Array<String>) {
val conn = DriverManager.getConnection( "jdbc:sqlite:./sampledb.db")
var stmt: Statement? = null
var resultset: ResultSet? = null
try {
stmt = conn.createStatement()
resultset = stmt!!.executeQuery("SELECT * FROM items;")
if (stmt.execute("SELECT * FROM items;")) {
resultset = stmt.resultSet
}
} catch (ex: SQLException) {
// handle any errors
ex.printStackTrace()
}
HttpServer.create(InetSocketAddress(8080), 0).apply {
println("browse http://localhost:8080/hello")
createContext("/hello") { http ->
http.responseHeaders.add("Content-type", "text/plain")
http.sendResponseHeaders(200, 0);
PrintWriter(http.responseBody).use { out ->
out.println( "ok")
while (resultset!!.next()) {
out.println(resultset.getString("name"))
}
}
}
start()
}
}
Please check the full documentation on Github.

Answer 4

As soon as you mention server then you are perhaps looking in the wrong direction. SQLite is intended as an embedded database, each device having it's unique database. Synchronisation between server and clients would have to be written and can be problematic, whilst there are many RDBMS's that cater for better for client-server solutions.
Have a look at Appropriate Uses For SQLite.