Kotlin Object Multiplatform Mapper (KOMM)

The Kotlin Object Multiplatform Mapper provides you a possibility to generate (via KSP) extension function to map one object to another.

• Features
• Default plugins
• Usage
  • Add
    • JVM project
    • Multiplatform project
  • Simple mapping
  • Configuration
    • Disable AutoCast
    • Change Convert Function Name
  • @MapName
  • @MapConverter
  • @MapDefault
  • @NullSubstitute
    • Allow Not-Null Assertion
  • Multi Sources
• Plugins
  • Iterable Plugin - Collections Mapping
    • Add
      • JVM project
      • Multiplatform project
    • Allow NotNullAssertion
    • NullSubstitute
  • Exposed Plugin - ResultRow Mapping
    • Add
    • Usage

---

Features

• Supports KSP Multiplatform
• Maps as constructor parameters as well as public properties with setter
• Supports properties types cast
• Supports Java objects get* functions
• Supports multi source classes with separated configurations
• Has next properties annotations:
  • Specify mapping from property with different name
  • Specify a converter to map data from source unusual way
  • Specify a resolver to map default values into properties
  • Specify null substitute to map nullable properties into not-nullable
• Support extension via plugins

Default plugins

• Iterable Plugin:
  • Support collections mapping with different types of elements

Usage

Add with Gradle

JVM Project

plugins {
    id("com.google.devtools.ksp") version "2.0.20-1.0.25"
}

val kommVersion = "0.20.2"

depensencies {
    implementation("com.ucasoft.komm:komm-annotations:$kommVersion")
    ksp("com.ucasoft.komm:komm-processor:$kommVersion")
}

Multiplatform Project

plugins {
    id("com.google.devtools.ksp") version "2.0.20-1.0.25"
}

val kommVersion = "0.20.2"

kotlin {
    jvm {
        withJava()
    }
    js(IR) {
        nodejs()
    }
    // Add other platforms
    sourceSets {
        val commonMain by getting {
            dependencies {
                implementation("com.ucasoft.komm:komm-annotations:$kommVersion")
            }
        }
        val jvmMain by getting
        val jsMain by getting
        // Init other sourceSets
    }
}

dependencies {
    add("kspJvm", "com.ucasoft.komm:komm-processor:$kommVersion")
    add("kspJs", "com.ucasoft.komm:komm-processor:$kommVersion")
    // Add other platforms like `kspAndroidNativeX64`, `kspLinuxX64`, `kspMingwX64` etc.
}

Simple Mapping

Classes declaration

class SourceObject {

    val id = 150

    val intToString = 300

    val stringToInt = "250"
}

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    val id: Int,
    val stringToInt: Int
) {
    var intToString: String = ""
}

or

@KOMMMap(to = [DestinationObject::class])
class SourceObject {

    val id = 150

    val intToString = 300

    val stringToInt = "250"
}

data class DestinationObject(
    val id: Int,
    val stringToInt: Int
) {
    var intToString: String = ""
}

Generated extension function

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    id = id,
    stringToInt = stringToInt.toInt()
).also { 
    it.intToString = intToString.toString()
}

Mapping Configuration

Disable AutoCast

Classes declaration

@KOMMMap(
    from = [SourceObject::class],
    config = MapConfiguration(
        tryAutoCast = false
    )
)
data class DestinationObject(
    val id: Int,
    val stringToInt: Int
) {
    var intToString: String = ""
}

Generation result

e: [ksp] com.ucasoft.komm.processor.exceptions.KOMMCastException: AutoCast is turned off! You have to use @MapConvert annotation to cast (stringToInt: Int) from (stringToInt: String)

Change Convert Function Name

Classes declaration

@KOMMMap(
    from = [SourceObject::class],
    config = MapConfiguration(
        convertFunctionName = "convertToDestination"
    )
)
data class DestinationObject(
    val id: Int,
    val stringToInt: Int
) {
    var intToString: String = ""
}

Generated extension function

fun SourceObject.convertToDestination(): DestinationObject = DestinationObject(
    id = id,
    stringToInt = stringToInt.toInt()
).also { 
    it.intToString = intToString.toString()
}

@MapName annotation

Classes declaration

class SourceObject {
    //...
    val userName = "user"
}

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    //...
    @MapName("userName")
    val name: String
) {
    var intToString: String = ""
}

or

@KOMMMap(to = [DestinationObject::class])
class SourceObject {
    //...
    @MapName("name")
    val userName = "user"
}

data class DestinationObject(
    //...
    val name: String
) {
    var intToString: String = ""
}

Generated extension function

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    //...
    name = userName
).also { 
    it.intToString = intToString.toString()
}

Use Converter

Converter declaration

class CostConverter(source: SourceObject) : KOMMConverter<SourceObject, Double, String>(source) {

    override fun convert(sourceMember: Double) = "$sourceMember ${source.currency}"
}

Classes declaration

class SourceObject {
    //...
    val cost = 499.99
}

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    //...
    @MapConvert<SourceObject, CostConverter>(CostConverter::class)
    val cost: String
) {
    //...
    @MapConvert<SourceObject, CostConverter>(CostConverter::class, "cost")
    var otherCost: String = ""
}

Generated extension function

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    //...
    cost = CostConverter(this).convert(cost)
).also { 
    //...
    it.otherCost = CostConverter(this).convert(cost)
}

Use Resolver

Resolver declaration

class DateResolver(destination: DestinationObject?) : KOMMResolver<DestinationObject, Date>(destination) {
    
    override fun resolve(): Date = Date.from(Instant.now())
}

Classes declaration

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    //...
    @MapDefault<DateResolver>(DateResolver::class)
    val activeDate: Date
) {
    //...
    @MapDefault<DateResolver>(DateResolver::class)
    var otherDate: Date = Date.from(Instant.now())
}

Generated extension function

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    //...
    activeDate = DateResolver(null).resolve()
).also { 
    //...
    it.otherDate = DateResolver(it).resolve()
}

Use NullSubstitute

Mapping configuration

Classes declaration

@KOMMMap(
    from = [SourceObject::class],
    config = MapConfiguration(
      allowNotNullAssertion = true
    )
)
data class DestinationObject(
    val id: Int
)
data class SourceObject(
    val id: Int?
)

Generated extension function

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    id = id!!
)

Otherwise

e: [ksp] com.ucasoft.komm.processor.exceptions.KOMMCastException: Auto Not-Null Assertion is not allowed! You have to use @NullSubstitute annotation for id property.

Resolver declaration

class IntResolver(destination: DestinationObject?): KOMMResolver<DestinationObject, Int>(destination) {

    override fun resolve() = 1
}

Classes declaration Map From

@KOMMMap(
    from = [SourceObject::class]
)
data class DestinationObject(
    @NullSubatitute(MapDefault(IntResolver::class))
    val id: Int
) {
    @NullSubatitute(MapDefault(IntResolver::class), "id")
    var otherId: Int = 0
}

Generated extension function for Map From

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    id = id ?: IntResolver(null).resolve()
).also {
    it.otherId = id ?: IntResolver(it).resolve()
}

Classes declaration Map To

@KOMMMap(
    to = [DestinationObject::class]
)
data class SourceObject(
    @NullSubatitute(MapDefault(IntResolver::class))
    val id: Int?
) 

Generated extension function for Map To

fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    id = id ?: IntResolver(null).resolve()
)

Multi Sources Support

Classes declaration

@KOMMMap(
    from = [FirstSourceObject::class, SecondSourceObject::class]
)
data class DestinationObject(
    @NullSubatitute(MapDefault(IntResolver::class), [FirstSourceObject::class])
    @MapName("userId", [SecondSourceObject::class])
    val id: Int
) {
    @NullSubatitute(MapDefault(IntResolver::class), "id", [FirstSourceObject::class])
    var otherId: Int = 0
}

data class FirstSourceObject(
  val id: Int?
)

data class SecondSourceObject(
    val userId: Int
)

in case, different sources should be configured different:

@KOMMMap(
    from = [FirstSourceObject::class],
    config = MapConfiguration(
        allowNotNullAssertion = true
    )
)
@KOMMMap(
    from = [SecondSourceObject::class]
)
data class DestinationObject(
  @NullSubatitute(MapDefault(IntResolver::class), [FirstSourceObject::class])
  @MapName("userId", [SecondSourceObject::class])
  val id: Int
) {
  @NullSubatitute(MapDefault(IntResolver::class), "id", [FirstSourceObject::class])
  var otherId: Int = 0
}

Generated extension functions

fun FirstSourceObject.toDestinationObject(): DestinationObject = DestinationObject(
    id = id ?: IntResolver(null).resolve()
).also {
    it.otherId = id ?: IntResolver(it).resolve()
}

fun SecondSourceObject.toDestinationObject(): DestinationObject = DestinationObject(
  id = userId
)

Plugins

Iterable Plugin - Collections Mapping

Add with Gradle

JVM Project

plugins {
    id("com.google.devtools.ksp") version "2.0.20-1.0.25"
}

val kommVersion = "0.20.2"

depensencies {
    implementation("com.ucasoft.komm:komm-annotations:$kommVersion")
    ksp("com.ucasoft.komm:komm-processor:$kommVersion")
    ksp("com.ucasoft.komm:komm-plugins-iterable:$kommVersion")
}

Multiplatform Project

plugins {
    id("com.google.devtools.ksp") version "2.0.20-1.0.25"
}

val kommVersion = "0.20.2"

//...

dependencies {
    add("kspJvm", "com.ucasoft.komm:komm-plugins-iterable:$kommVersion")
    add("kspJvm", "com.ucasoft.komm:komm-processor:$kommVersion")
    add("kspJs", "com.ucasoft.komm:komm-plugins-iterable:$kommVersion")
    add("kspJs", "com.ucasoft.komm:komm-processor:$kommVersion")
    // Add other platforms like `kspAndroidNativeX64`, `kspLinuxX64`, `kspMingwX64` etc.
}

Allow NotNullAssertion

Classes declaration

class SourceObject {
    val intList: List<Int>? = listOf(1, 2, 3)
}

@KOMMMap(from = [SourceObject::class], config = MapConfiguration(allowNotNullAssertion = true))
data class DestinationObject(
    @MapName("intList")
    val stringList: MutableList<String>
)

Generated extension function

public fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
	stringList = intList!!.map { it.toString() }.toMutableList()
)

NullSubstitute

Classes declaration

class SourceObject {
    val intList: List<Int>? = listOf(1, 2, 3)
}

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    @NullSubstitute(MapDefault(StringListResolver::class), "intList")
    val stringList: MutableList<String>
)

Generated extension function

public fun SourceObject.toDestinationObject(): DestinationObject = DestinationObject(
	stringList = intList?.map { it.toString() }?.toMutableList() ?: StringListResolver(null).resolve()
)

Exposed Plugin - ResultRow Mapping

Add with Gradle

JVM Project

plugins {
    id("com.google.devtools.ksp") version "2.0.20-1.0.25"
}

val kommVersion = "0.20.2"

depensencies {
    implementation("com.ucasoft.komm:komm-annotations:$kommVersion")
    ksp("com.ucasoft.komm:komm-processor:$kommVersion")
    ksp("com.ucasoft.komm:komm-plugins-exposed:$kommVersion")
}

Usage

Classes declaration

object SourceObject: Table() {
    val id = integer("id").autoIncrement()
    val name = varchar("name", 255)
    val age = integer("age")

    override val primaryKey = PrimaryKey(id)
}

@KOMMMap(from = [SourceObject::class])
data class DestinationObject(
    val id: Int,
    val name: String,
    val age: Int
)

Generated extension function

public fun ResultRow.toDestinationObject(): DestinationObject = DestinationObject(
    id = this[SourceObject.id],
    name = this[SourceObject.name],
    age = this[SourceObject.age]
)