JarCastingKomapper: Kotlin SQL Mapper
Komapper is a simple database access library for Kotlin 1.5 and later.
For more documentation, go to our site: https://www.komapper.org/docs/.
Features
- compile-time code generation using Kotlin Symbol Processing API
- annotation-free data models
- value class support
- immutable and composable queries
- upsert (insert-or-update) query support
Examples
Data model and mapping definition
// Data model: this class doesn't require any annotations.
data class Address(
val id: Int = 0,
val street: String,
val version: Int = 0,
val createdAt: LocalDateTime? = null,
val updatedAt: LocalDateTime? = null,
)
// Mapping definition: this class maps the ADDRESS table and the Address class.
@KmEntityDef(Address::class)
data class AddressDef(
@KmId @KmAutoIncrement @KmColumn(name = "ADDRESS_ID")
val id: Nothing,
@KmVersion val version: Nothing,
@KmCreatedAt val createdAt: Nothing,
@KmUpdatedAt val updatedAt: Nothing,
) {
companion object
}
Entity DSL
Select
// get a generated metamodel
val a = AddressDef.meta
// select all
EntityDsl.from(a)
// select by id
EntityDsl.from(a).first { a.id eq 1 }
// select by multiple conditions
EntityDsl.from(a).where {
a.street like "A%"
a.createdAt greater LocalDateTime.of(2020, 1, 1, 0, 0)
}.orderBy(a.id)
val e = EmployeeDef.meta
val d = DepartmentDef.meta
// select using join operations
EntityDsl.from(e)
.innerJoin(a) { e.addressId eq a.id }
.leftJoin(d) { e.departmentId eq d.id }
.where { d.location eq "TOKYO" }
.orderBy(e.id)
.associate(e, a) { employee, address -> employee.copy(address = address) }
.associate(e, d) { employee, department -> employee.copy(department = department) }
Insert
val a = AddressDef.meta
// insert single entity
EntityDsl.insert(a).single(Address(street = "STREET A"))
// insert multiple entities at once
EntityDsl.insert(a).multiple(
Address(street = "STREET A"),
Address(street = "STREET B"),
)
// insert or update single entity
EntityDsl.insert(a)
.onDuplicateKeyUpdate(a.street)
.single(Address(street = "STREET A"))
Update
val a = AddressDef.meta
val address = ...
// update single entity
EntityDsl.update(a).single(address)
Delete
val a = AddressDef.meta
val address = ...
// delete single entity
EntityDsl.delete(a).single(address)
SQL DSL
Select
val e = EmployeeDef.meta
val d = DepartmentDef.meta
// union
val q1 = SqlDsl.from(e).select(e.name)
val q2 = SqlDsl.from(d).select(d.name)
val unionQuery = q1 union q2
// group by and having
SqlDsl.from(e)
.groupBy(e.departmentId)
.having { count(e.id) greaterEq 4 }
.orderBy(e.departmentId)
.select(e.departmentId, count(e.id))
Insert
val a = AddressDef.meta
SqlDsl.insert(a).values {
a.street set "STREET 16"
a.version set 0
a.createdAt set LocalDateTime.now()
a.updatedAt set LocalDateTime.now()
}
Update
val a = AddressDef.meta
SqlDsl.update(a).set {
a.street set "STREET X"
a.version set (a.version + 10)
}.where {
a.id eq 1
}
Delete
val a = AddressDef.meta
SqlDsl.delete(a).where {
a.id inList listOf(1, 2, 3)
}
