Kotlin support¶
Contents
Doma supports Kotlin 1.4.0 or later.
Best practices¶
Here are some recommended methods, such as defining classes and building them with Kotlin.
Entity classes¶
- Define as a plain class
- Specify a
Metamodel
annotation to themetamodel
element of@Entity
@Entity(metamodel = Metamodel())
class Person : AbstractPerson() {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
var id: Int = -1
var name: Name? = null
var age: Int? = -1
var address: Address? = null
@Column(name = "DEPARTMENT_ID")
var departmentId: Int = -1
@Version
var version: Int = -1
}
Domain classes¶
- Define as a data class
- Define only one constructor
- Define only one property whose name is
value
in the constructor - Use val for the property definition
@Domain(valueType = String::class)
data class Name(val value: String)
Embeddable classes¶
- Define as a data class
- Define only one constructor
- Define properties only in the constructor
- Use val for the property definitions
@Embeddable
data class Address(val city: String, val street: String)
Dao interfaces¶
- Specify a SQL template to
@org.seasar.doma.Sql
- Use
org.seasar.doma.jdbc.Result
as the return type of@Delete
,@Insert
and@Update
- Use
org.seasar.doma.jdbc.BatchResult
as the return type of@BatchDelete
,@BatchInsert
and@BatchUpdate
@Dao
interface PersonDao {
@Sql("""
select * from person where id = /*id*/0
""")
@Select
fun selectById(id: Int): Person
@Insert
fun insert(Person person): Result<Person>
}
- Use Destructuring Declarations
for
org.seasar.doma.jdbc.Result
andorg.seasar.doma.jdbc.BatchResult
val dao: PersonDao = ...
val person = Person(name = Name("Jhon"), address = Address(city = "Tokyo", street = "Yaesu"))
val (newPerson, count) = dao.insert(person)
Kotlin specific Criteria API¶
Note
Prefer the Kotlin specific Criteria API to DAO interfaces.
Doma provides Kotlin specific Criteria API, KEntityql
and KNativeQl
DSLs.
They are very similar with the Entityql
and NativeQl
DSLs, which are described in Criteria API.
The biggest feature of the KEntityql
and KNativeQl
DSLs is simplicity.
For example, when you use KEntityql
, you have to accept a lambda parameter in a WHERE expression as follows:
val entityql = Entityql(config)
val e = Employee_()
val list = entityql
.from(e)
.where { c ->
c.eq(e.departmentId, 2)
c.isNotNull(e.managerId)
c.or {
c.gt(e.salary, Salary("1000"))
c.lt(e.salary, Salary("2000"))
}
}
.fetch()
The lambda parameter c
is a bit annoying.
On the other hand, when you use KEntityql
, the parameter is gone.
val entityql = KEntityql(config)
val e = Employee_()
val list = entityql
.from(e)
.where {
eq(e.departmentId, 2)
isNotNull(e.managerId)
or {
gt(e.salary, Salary("1000"))
lt(e.salary, Salary("2000"))
}
}
.fetch()
You can see a lot of sample code here.
The KEntityql
and KNativeQl
DSLs are included in doma-kotlin.jar.
Note that you should depend on doma-kotlin instead of doma-core in your build script.
You can write build.gradle.kts as follows:
dependencies {
implementation("org.seasar.doma:doma-kotlin:2.47.1")
}
Code Generation¶
Use Doma CodeGen Plugin. This plugin support Kotlin code generation.
Using kapt in Gradle¶
Annotation processors are supported in Kotlin with the kapt compiler plugin.
Add the dependencies using the kapt and implementation configuration in your dependencies block. For example, you can write build.gradle.kts as follows:
dependencies {
kapt("org.seasar.doma:doma-processor:2.47.1")
implementation("org.seasar.doma:doma-kotlin:2.47.1")
}
To simplify your build script, we recommend you use the Doma Compile Plugin: