Add database migrations and user table / migration

README.md

@@ -1,5 +1,27 @@
 # Boruto
 
+## Database
+
+The server runs database migrations before Javalin starts.
+
+By default, it connects to:
+
+```text
+jdbc:postgresql://localhost:5432/boruto
+username: boruto
+password: boruto
+```
+
+Override those values with:
+
+- `DATABASE_URL` or `JDBC_DATABASE_URL`
+- `DATABASE_USERNAME`, `POSTGRES_USER`, or `DB_USER`
+- `DATABASE_PASSWORD`, `POSTGRES_PASSWORD`, or `DB_PASSWORD`
+
+Migrations are classes in `dev.mduchene.database.migrations`. The migration
+runner discovers classes in that package and runs unapplied migrations ordered by
+class name.
+
 ## Documentation
 
 - [SQL Builder](docs/sql-builder.md)

pom.xml

@@ -97,6 +97,12 @@
             <artifactId>javalin</artifactId>
             <version>7.2.2</version>
         </dependency>
+
+        <dependency>
+            <groupId>org.postgresql</groupId>
+            <artifactId>postgresql</artifactId>
+            <version>42.7.11</version>
+        </dependency>
     </dependencies>
 
-</project>
+</project>

src/main/kotlin/Main.kt

@@ -1,9 +1,15 @@
 package dev.mduchene
 
+import dev.mduchene.database.DatabaseConfig
+import dev.mduchene.database.migration.DatabaseMigrator
 import io.javalin.Javalin
 
 fun main() {
-  val app = Javalin.create { config ->
+  DatabaseConfig.fromEnvironment().openConnection().use { connection ->
+    DatabaseMigrator("dev.mduchene.database.migrations").migrate(connection)
+  }
+
+  Javalin.create { config ->
     config.routes.get("/") { ctx -> ctx.result("Hello World") }
   }.start(7070)
-}
+}

src/main/kotlin/dev/mduchene/database/DatabaseConfig.kt

@@ -0,0 +1,42 @@
+package dev.mduchene.database
+
+import java.sql.Connection
+import java.sql.DriverManager
+
+data class DatabaseConfig(
+  val jdbcUrl: String,
+  val username: String,
+  val password: String,
+) {
+  fun openConnection(): Connection =
+    DriverManager.getConnection(jdbcUrl, username, password)
+
+  companion object {
+    fun fromEnvironment(environment: Map<String, String> = System.getenv()): DatabaseConfig =
+      DatabaseConfig(
+        jdbcUrl = environment.firstPresent(
+          "DATABASE_URL",
+          "JDBC_DATABASE_URL",
+          defaultValue = "jdbc:postgresql://localhost:5432/boruto",
+        ),
+        username = environment.firstPresent(
+          "DATABASE_USERNAME",
+          "POSTGRES_USER",
+          "DB_USER",
+          defaultValue = "root",
+        ),
+        password = environment.firstPresent(
+          "DATABASE_PASSWORD",
+          "POSTGRES_PASSWORD",
+          "DB_PASSWORD",
+          defaultValue = "root",
+        ),
+      )
+  }
+}
+
+private fun Map<String, String>.firstPresent(
+  vararg keys: String,
+  defaultValue: String,
+): String =
+  keys.firstNotNullOfOrNull { key -> this[key]?.takeIf(String::isNotBlank) } ?: defaultValue

src/main/kotlin/dev/mduchene/database/migration/DatabaseMigration.kt

@@ -0,0 +1,10 @@
+package dev.mduchene.database.migration
+
+import java.sql.Connection
+
+interface DatabaseMigration {
+  val name: String
+    get() = javaClass.simpleName
+
+  fun migrate(connection: Connection)
+}

src/main/kotlin/dev/mduchene/database/migration/DatabaseMigrator.kt

@@ -0,0 +1,151 @@
+package dev.mduchene.database.migration
+
+import java.io.File
+import java.lang.reflect.Modifier
+import java.net.JarURLConnection
+import java.net.URL
+import java.sql.Connection
+import java.util.jar.JarFile
+
+class DatabaseMigrator(
+  private val migrationsPackage: String,
+  private val classLoader: ClassLoader = Thread.currentThread().contextClassLoader,
+) {
+  fun migrate(connection: Connection) {
+    val originalAutoCommit = connection.autoCommit
+    connection.autoCommit = false
+
+    try {
+      ensureMigrationTable(connection)
+      val appliedMigrations = appliedMigrationNames(connection)
+
+      discoverMigrations()
+        .filterNot { migration -> migration.name in appliedMigrations }
+        .forEach { migration ->
+          migration.migrate(connection)
+          recordMigration(connection, migration.name)
+          connection.commit()
+        }
+
+      connection.commit()
+    } catch (exception: Exception) {
+      connection.rollback()
+      throw exception
+    } finally {
+      connection.autoCommit = originalAutoCommit
+    }
+  }
+
+  fun discoverMigrations(): List<DatabaseMigration> =
+    classNamesInPackage()
+      .map { className -> Class.forName(className, true, classLoader) }
+      .filter { migrationClass ->
+        DatabaseMigration::class.java.isAssignableFrom(migrationClass) &&
+          !migrationClass.isInterface &&
+          !Modifier.isAbstract(migrationClass.modifiers)
+      }
+      .map { migrationClass ->
+        migrationClass.getDeclaredConstructor().newInstance() as DatabaseMigration
+      }
+      .sortedBy(DatabaseMigration::name)
+
+  private fun ensureMigrationTable(connection: Connection) {
+    connection.createStatement().use { statement ->
+      statement.executeUpdate(
+        """
+        CREATE TABLE IF NOT EXISTS schema_migrations (
+          name VARCHAR(255) PRIMARY KEY,
+          applied_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP
+        )
+        """.trimIndent(),
+      )
+    }
+  }
+
+  private fun appliedMigrationNames(connection: Connection): Set<String> =
+    connection.createStatement().use { statement ->
+      statement.executeQuery("SELECT name FROM schema_migrations").use { results ->
+        buildSet {
+          while (results.next()) {
+            add(results.getString("name"))
+          }
+        }
+      }
+    }
+
+  private fun recordMigration(
+    connection: Connection,
+    migrationName: String,
+  ) {
+    connection.prepareStatement("INSERT INTO schema_migrations (name) VALUES (?)").use { statement ->
+      statement.setString(1, migrationName)
+      statement.executeUpdate()
+    }
+  }
+
+  private fun classNamesInPackage(): List<String> {
+    val packagePath = migrationsPackage.replace('.', '/')
+    val resources = classLoader.getResources(packagePath).toList()
+
+    return resources.flatMap { resource ->
+      when (resource.protocol) {
+        "file" -> classNamesFromDirectory(resource)
+        "jar" -> classNamesFromJar(resource, packagePath)
+        else -> emptyList()
+      }
+    }.distinct()
+  }
+
+  private fun classNamesFromDirectory(resource: URL): List<String> {
+    val root = File(resource.toURI())
+
+    return root
+      .walkTopDown()
+      .filter { file -> file.isFile && file.extension == "class" && '$' !in file.name }
+      .map { file ->
+        val relativeClassName = root
+          .toPath()
+          .relativize(file.toPath())
+          .toString()
+          .removeSuffix(".class")
+          .replace(File.separatorChar, '.')
+
+        "$migrationsPackage.$relativeClassName"
+      }
+      .toList()
+  }
+
+  private fun classNamesFromJar(
+    resource: URL,
+    packagePath: String,
+  ): List<String> {
+    val connection = resource.openConnection()
+
+    return when (connection) {
+      is JarURLConnection -> classNamesFromJar(connection.jarFile, packagePath)
+      else -> emptyList()
+    }
+  }
+
+  private fun classNamesFromJar(
+    jarFile: JarFile,
+    packagePath: String,
+  ): List<String> =
+    jarFile
+      .entries()
+      .asSequence()
+      .map { entry -> entry.name }
+      .filter { name -> name.startsWith(packagePath) && name.endsWith(".class") && '$' !in name }
+      .map { name -> name.removeSuffix(".class").replace('/', '.') }
+      .toList()
+}
+
+private fun <T> java.util.Enumeration<T>.toList(): List<T> {
+  val values = mutableListOf<T>()
+
+  while (hasMoreElements()) {
+    values += nextElement()
+  }
+
+  return values
+}

src/main/kotlin/dev/mduchene/database/migrations/V001CreateUsersTable.kt

@@ -0,0 +1,22 @@
+package dev.mduchene.database.migrations
+
+import dev.mduchene.database.migration.DatabaseMigration
+import java.sql.Connection
+
+class V001CreateUsersTable : DatabaseMigration {
+  override fun migrate(connection: Connection) {
+    connection.createStatement().use { statement ->
+      statement.executeUpdate(
+        """
+        CREATE TABLE IF NOT EXISTS users (
+          id BIGINT GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
+          username VARCHAR(255) NOT NULL UNIQUE,
+          password_hash VARCHAR(255) NOT NULL,
+          created_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP,
+          updated_at TIMESTAMP WITH TIME ZONE NOT NULL DEFAULT CURRENT_TIMESTAMP
+        )
+        """.trimIndent(),
+      )
+    }
+  }
+}

src/test/kotlin/dev/mduchene/database/migration/DatabaseMigratorTest.kt

@@ -0,0 +1,18 @@
+package dev.mduchene.database.migration
+
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class DatabaseMigratorTest {
+  @Test
+  fun `discovers migrations from a package ordered by migration name`() {
+    val migrations = DatabaseMigrator("dev.mduchene.database.migration.fixture")
+      .discoverMigrations()
+      .map(DatabaseMigration::name)
+
+    assertEquals(
+      listOf("V001FirstMigration", "V002SecondMigration"),
+      migrations,
+    )
+  }
+}

src/test/kotlin/dev/mduchene/database/migration/fixture/TestMigrations.kt

@@ -0,0 +1,12 @@
+package dev.mduchene.database.migration.fixture
+
+import dev.mduchene.database.migration.DatabaseMigration
+import java.sql.Connection
+
+class V002SecondMigration : DatabaseMigration {
+  override fun migrate(connection: Connection) = Unit
+}
+
+class V001FirstMigration : DatabaseMigration {
+  override fun migrate(connection: Connection) = Unit
+}