Komapper: Kotlin ORM for JDBC and R2DBC

Komapper is an ORM library for server-side Kotlin.

For more documentation, go to our site:

• https://www.komapper.org/docs/

Features

Highlighted

• Support for both JDBC and R2DBC
• Code generation at compile-time using Kotlin Symbol Processing API
• Immutable and composable queries
• Support for Kotlin value classes
• Easy Spring Boot integration

Experimental

• Quarkus integration
• Transaction management using context receivers

Prerequisite

• Kotlin 1.9.24 or later
• JRE 11 or later
• Gradle 6.8.3 or later

Supported Databases

Komapper is tested with the following databases:

Supported connectivity types:

• JDBC 4.3
• R2DBC 1.0.0

Installation

Add the following code to the Gradle build script (gradle.build.kts).

plugins {
    kotlin("jvm") version "2.1.10"
    id("com.google.devtools.ksp") version "2.1.10-1.0.31"
}
val komapperVersion = "5.2.1"
dependencies {
    platform("org.komapper:komapper-platform:$komapperVersion").let {
        implementation(it)
        ksp(it)
    }
    implementation("org.komapper:komapper-starter-jdbc")
    implementation("org.komapper:komapper-dialect-h2-jdbc")
    ksp("org.komapper:komapper-processor")
}

See also Quickstart for more details:

• https://www.komapper.org/docs/quickstart/

Sample code

To get complete code, go to our example repository.

Entity class definition

@KomapperEntity
data class Address(
    @KomapperId
    @KomapperAutoIncrement
    @KomapperColumn(name = "ADDRESS_ID")
    val id: Int = 0,
    val street: String,
    @KomapperVersion
    val version: Int = 0,
    @KomapperCreatedAt
    val createdAt: LocalDateTime? = null,
    @KomapperUpdatedAt
    val updatedAt: LocalDateTime? = null,
)

Connecting with JDBC

fun main() {
    // create a Database instance
    val db = JdbcDatabase("jdbc:h2:mem:example;DB_CLOSE_DELAY=-1")
    // get a metamodel
    val a = Meta.address
    // execute simple operations in a transaction
    db.withTransaction {
        // create a schema
        db.runQuery {
            QueryDsl.create(a)
        }
        // INSERT
        val newAddress = db.runQuery {
            QueryDsl.insert(a).single(Address(street = "street A"))
        }
        // SELECT
        val address = db.runQuery {
            QueryDsl.from(a).where { a.id eq newAddress.id }.first()
        }
    }
}

Connecting with R2DBC

suspend fun main() {
    // create a Database instance
    val db = R2dbcDatabase("r2dbc:h2:mem:///example;DB_CLOSE_DELAY=-1")
    // get a metamodel
    val a = Meta.address
    // execute simple operations in a transaction
    db.withTransaction {
        // create a schema
        db.runQuery {
            QueryDsl.create(a)
        }
        // INSERT
        val newAddress = db.runQuery {
            QueryDsl.insert(a).single(Address(street = "street A"))
        }
        // SELECT
        val address = db.runQuery {
            QueryDsl.from(a).where { a.id eq newAddress.id }.first()
        }
    }
}

Design Policy

See DESIGN_DOC for the design policy of this project.

Compatibility Matrix

Compatibility testing is performed in the komapper/compatibility-test repository.

Backers

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