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Kraft

Compile-time mapper generation for Kotlin Multiplatform.

Kraft is a KSP-based annotation processor that generates type-safe extension functions to map between data classes. No reflection, no runtime overhead — just clean, generated Kotlin code.

Features

  • Annotation-driven — @MapConfig, @MapFrom, or @MapTo to declare mappings
  • Property matching — same-name properties mapped automatically
  • Field renaming — @MapField or @FieldMapping for cross-name mapping
  • Nested objects — auto-detected when types differ, with implicit child mapper generation; use @MapField / FieldMapping for renamed pairs (@MapNested is deprecated)
  • Collections — List<T> and Set<T> with nested element mapping
  • Enum mapping — @MapEnum with auto-matching and custom entry pairs
  • Custom converters — @MapUsing for property-source or whole-source transformations
  • Global converters — @KraftConverter on a top-level extension is auto-discovered across the module and the classpath, with @OptIn markers propagated onto the generated mapper
  • Reverse mapping — @MapReverse generates the inverse mapper automatically
  • Layer-aware aliases — register Dto / Domain / Entity sides via Gradle to emit short .toDomain() / .toEntity() extensions alongside the verbose mappers
  • Ignore rules — @MapIgnore and @MapIgnoreField with directional control
  • Plugin SPI — implement MapperGeneratorProvider to plug in your own code generator
  • Kotlin Multiplatform — annotations work on JVM, iOS, JS, and WasmJs

Quick Start

JVM / Android:

// build.gradle.kts
plugins {
    id("com.google.devtools.ksp") version "2.3.3"
}

dependencies {
    implementation("com.blu3berry.kraft:kraft-annotations:<version>")
    ksp("com.blu3berry.kraft:kraft-ksp:<version>")
}

Kotlin Multiplatform:

// build.gradle.kts
plugins {
    id("com.google.devtools.ksp") version "2.3.3"
}

kotlin {
    sourceSets {
        commonMain.dependencies {
            implementation("com.blu3berry.kraft:kraft-annotations:<version>")
        }
    }
}

dependencies {
    add("kspCommonMainMetadata", "com.blu3berry.kraft:kraft-ksp:<version>")
}

See Getting Started for full installation details.

data class User(val id: Int, val name: String, val email: String)
data class UserDto(val id: Int, val name: String, val email: String)

@MapConfig(source = User::class, target = UserDto::class)
object UserMapper

// Generated: fun User.toUserDto(): UserDto

Documentation