Welcome to Exposed, an ORM framework for Kotlin.

Exposed is a lightweight SQL library on top of JDBC driver for Kotlin language. Exposed has two flavors of database access: typesafe SQL wrapping DSL and lightweight Data Access Objects (DAO).

With Exposed you can have two levels of databases Access. You would like to use exposed because the database access includes wrapping DSL and a lightweight data access object. Also, our official mascot is Cuttlefish, which is well known for its outstanding mimicry ability that enables it to blend seamlessly in any environment. Similar to our mascot, Exposed can be used to mimic a variety of database engines and help you build applications without dependencies on any specific database engine and switch between them with very little or no changes.

Supported Databases

• (Also, PostgreSQL using the pgjdbc-ng JDBC driver)
• 
• 
• 
• H2
• Oracle
• SQL Server

Links

Currently, Exposed is available for maven/gradle builds. Check the Maven Central and read (Getting started) to get an insight on setting up Exposed.

For more information visit the links below:

• Wiki with examples and docs
• Roadmap to see what's coming next
• Change log of improvements and bug fixes
• Slack Channel
  
  

Community

Do you have questions? Feel free to ask and join our project conversation at our #exposed channel on kotlinlang.slack.com.

Pull requests

We actively welcome your pull requests. However, linking your work to an existing issue is preferred.

• Fork the repo and create your branch from main.
• Name your branch something that is descriptive to the work you are doing. i.e. adds-new-thing.
• If you've added code that should be tested, add tests and ensure the test suite passes.
• Make sure you address any lint warnings.
• If you make the existing code better, please let us know in your PR description.

Examples

SQL DSL

import org.jetbrains.exposed.sql.*
import org.jetbrains.exposed.sql.transactions.transaction

object Users : Table() {
    val id = varchar("id", 10) // Column<String>
    val name = varchar("name", length = 50) // Column<String>
    val cityId = (integer("city_id") references Cities.id).nullable() // Column<Int?>

    override val primaryKey = PrimaryKey(id, name = "PK_User_ID") // name is optional here
}

object Cities : Table() {
    val id = integer("id").autoIncrement() // Column<Int>
    val name = varchar("name", 50) // Column<String>

    override val primaryKey = PrimaryKey(id, name = "PK_Cities_ID")
}

fun main() {
    Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver", user = "root", password = "")

    transaction {
        addLogger(StdOutSqlLogger)

        SchemaUtils.create (Cities, Users)

        val saintPetersburgId = Cities.insert {
            it[name] = "St. Petersburg"
        } get Cities.id

        val munichId = Cities.insert {
            it[name] = "Munich"
        } get Cities.id

        val pragueId = Cities.insert {
            it.update(name, stringLiteral("   Prague   ").trim().substring(1, 2))
        }[Cities.id]

        val pragueName = Cities.select { Cities.id eq pragueId }.single()[Cities.name]
        assertEquals(pragueName, "Pr")

        Users.insert {
            it[id] = "andrey"
            it[name] = "Andrey"
            it[Users.cityId] = saintPetersburgId
        }

        Users.insert {
            it[id] = "sergey"
            it[name] = "Sergey"
            it[Users.cityId] = munichId
        }

        Users.insert {
            it[id] = "eugene"
            it[name] = "Eugene"
            it[Users.cityId] = munichId
        }

        Users.insert {
            it[id] = "alex"
            it[name] = "Alex"
            it[Users.cityId] = null
        }

        Users.insert {
            it[id] = "smth"
            it[name] = "Something"
            it[Users.cityId] = null
        }

        Users.update({ Users.id eq "alex"}) {
            it[name] = "Alexey"
        }

        Users.deleteWhere{ Users.name like "%thing"}

        println("All cities:")

        for (city in Cities.selectAll()) {
            println("${city[Cities.id]}: ${city[Cities.name]}")
        }

        println("Manual join:")
        (Users innerJoin Cities).slice(Users.name, Cities.name).
            select {(Users.id.eq("andrey") or Users.name.eq("Sergey")) and
                    Users.id.eq("sergey") and Users.cityId.eq(Cities.id)}.forEach {
            println("${it[Users.name]} lives in ${it[Cities.name]}")
        }

        println("Join with foreign key:")


        (Users innerJoin Cities).slice(Users.name, Users.cityId, Cities.name).
                select { Cities.name.eq("St. Petersburg") or Users.cityId.isNull()}.forEach {
            if (it[Users.cityId] != null) {
                println("${it[Users.name]} lives in ${it[Cities.name]}")
            }
            else {
                println("${it[Users.name]} lives nowhere")
            }
        }

        println("Functions and group by:")

        ((Cities innerJoin Users).slice(Cities.name, Users.id.count()).selectAll().groupBy(Cities.name)).forEach {
            val cityName = it[Cities.name]
            val userCount = it[Users.id.count()]

            if (userCount > 0) {
                println("$userCount user(s) live(s) in $cityName")
            } else {
                println("Nobody lives in $cityName")
            }
        }

        SchemaUtils.drop (Users, Cities)
    }
}

Generated SQL:

    SQL: CREATE TABLE IF NOT EXISTS Cities (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(50) NOT NULL, CONSTRAINT PK_Cities_ID PRIMARY KEY (id))
    SQL: CREATE TABLE IF NOT EXISTS Users (id VARCHAR(10) NOT NULL, name VARCHAR(50) NOT NULL, city_id INT NULL, CONSTRAINT PK_User_ID PRIMARY KEY (id))
    SQL: ALTER TABLE Users ADD FOREIGN KEY (city_id) REFERENCES Cities(id)
    SQL: INSERT INTO Cities (name) VALUES ('St. Petersburg')
    SQL: INSERT INTO Cities (name) VALUES ('Munich')
    SQL: INSERT INTO Cities (name) VALUES ('Prague')
    SQL: INSERT INTO Users (id, name, city_id) VALUES ('andrey', 'Andrey', 1)
    SQL: INSERT INTO Users (id, name, city_id) VALUES ('sergey', 'Sergey', 2)
    SQL: INSERT INTO Users (id, name, city_id) VALUES ('eugene', 'Eugene', 2)
    SQL: INSERT INTO Users (id, name, city_id) VALUES ('alex', 'Alex', NULL)
    SQL: INSERT INTO Users (id, name, city_id) VALUES ('smth', 'Something', NULL)
    SQL: UPDATE Users SET name='Alexey' WHERE Users.id = 'alex'
    SQL: DELETE FROM Users WHERE Users.name LIKE '%thing'
    All cities:
    SQL: SELECT Cities.id, Cities.name FROM Cities
    1: St. Petersburg
    2: Munich
    3: Prague
    Manual join:
    SQL: SELECT Users.name, Cities.name FROM Users INNER JOIN Cities ON Cities.id = Users.city_id WHERE ((Users.id = 'andrey') or (Users.name = 'Sergey')) and Users.id = 'sergey' and Users.city_id = Cities.id
    Sergey lives in Munich
    Join with foreign key:
    SQL: SELECT Users.name, Users.city_id, Cities.name FROM Users INNER JOIN Cities ON Cities.id = Users.city_id WHERE (Cities.name = 'St. Petersburg') or (Users.city_id IS NULL)
    Andrey lives in St. Petersburg
    Functions and group by:
    SQL: SELECT Cities.name, COUNT(Users.id) FROM Cities INNER JOIN Users ON Cities.id = Users.city_id GROUP BY Cities.name
    1 user(s) live(s) in St. Petersburg
    2 user(s) live(s) in Munich
    SQL: DROP TABLE Users
    SQL: DROP TABLE Cities

DAO

import org.jetbrains.exposed.dao.*
import org.jetbrains.exposed.dao.id.EntityID
import org.jetbrains.exposed.dao.id.IntIdTable
import org.jetbrains.exposed.sql.*
import org.jetbrains.exposed.sql.transactions.transaction

object Users : IntIdTable() {
    val name = varchar("name", 50).index()
    val city = reference("city", Cities)
    val age = integer("age")
}

object Cities: IntIdTable() {
    val name = varchar("name", 50)
}

class User(id: EntityID<Int>) : IntEntity(id) {
    companion object : IntEntityClass<User>(Users)

    var name by Users.name
    var city by City referencedOn Users.city
    var age by Users.age
}

class City(id: EntityID<Int>) : IntEntity(id) {
    companion object : IntEntityClass<City>(Cities)

    var name by Cities.name
    val users by User referrersOn Users.city
}

fun main() {
    Database.connect("jdbc:h2:mem:test", driver = "org.h2.Driver", user = "root", password = "")

    transaction {
        addLogger(StdOutSqlLogger)

        SchemaUtils.create (Cities, Users)

        val stPete = City.new {
            name = "St. Petersburg"
        }

        val munich = City.new {
            name = "Munich"
        }

        User.new {
            name = "a"
            city = stPete
            age = 5
        }

        User.new {
            name = "b"
            city = stPete
            age = 27
        }

        User.new {
            name = "c"
            city = munich
            age = 42
        }

        println("Cities: ${City.all().joinToString {it.name}}")
        println("Users in ${stPete.name}: ${stPete.users.joinToString {it.name}}")
        println("Adults: ${User.find { Users.age greaterEq 18 }.joinToString {it.name}}")
    }
}

Generated SQL:

    SQL: CREATE TABLE IF NOT EXISTS Cities (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(50) NOT NULL, CONSTRAINT pk_Cities PRIMARY KEY (id))
    SQL: CREATE TABLE IF NOT EXISTS Users (id INT AUTO_INCREMENT NOT NULL, name VARCHAR(50) NOT NULL, city INT NOT NULL, age INT NOT NULL, CONSTRAINT pk_Users PRIMARY KEY (id))
    SQL: CREATE INDEX Users_name ON Users (name)
    SQL: ALTER TABLE Users ADD FOREIGN KEY (city) REFERENCES Cities(id)
    SQL: INSERT INTO Cities (name) VALUES ('St. Petersburg'),('Munich')
    SQL: SELECT Cities.id, Cities.name FROM Cities
    Cities: St. Petersburg, Munich
    SQL: INSERT INTO Users (name, city, age) VALUES ('a', 1, 5),('b', 1, 27),('c', 2, 42)
    SQL: SELECT Users.id, Users.name, Users.city, Users.age FROM Users WHERE Users.city = 1
    Users in St. Petersburg: a, b
    SQL: SELECT Users.id, Users.name, Users.city, Users.age FROM Users WHERE Users.age >= 18
    Adults: b, c

⚖️ LICENSE

By contributing to the Exposed project, you agree that your contributions will be licensed under Apache License, Version 2.0.