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:

| Database | version | JDBC support | R2DBC support | |--------------------|---------|:------------:|:-------------:| | H2 Database | 2.3.232 | v | v | | MariaDB | 10.6.3 | v | v | | MySQL v5.x | 5.7.44 | v | v | | MySQL v8.x | 8.0.25 | v | v | | Oracle Database XE | 18.4.0 | v | v | | PostgreSQL | 12.9 | v | v | | SQL Server | 2019 | v | (unstable) |

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 "2.2.21"
    id("com.google.devtools.ksp") version "2.3.0"
}

val komapperVersion = "6.0.0"

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

| Kotlin and KSP version | Komapper version | KSP2 support? | JRE min version | Gradle min version | |:-----------------------|:-----------------|---------------|:----------------|--------------------| | 1.9.24-1.0.20 | 1.18.1 - 2.x | No | 11 | 6.8.3 | | 2.0.21-1.0.28 | 2.x - 5.x | Yes | 11 | 7.6.4 | | 2.1.21-2.0.2 | 5.x | Yes | 11 | 7.6.4 | | 2.2.20-2.0.3 | 5.x | Yes | 11 | 7.6.4 | | 2.3.0 | 5.x | Yes | 11 | 7.6.4 |

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

Financial Contributors

Support Komapper's development on Open Collective.

Organizations

Individuals

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