Mappie

Mappie is a Kotlin Multiplatform compiler plugin which generates code to simplify developing object mapping code. Writing object mapping code is often a mind-numbing and error-prone task. Reducing this development effort will lead to a more pleasant programming experience, and less risk of bugs.

Mappie offers the following advantages:

• All code is generated at compile-time, without the need for any reflection at runtime. Making the generated code have the same runtime performance as if one would write the object mapping code manually.
• You write Kotlin code instead of String references, allowing your IDE to support you with automatic refactorings and auto-complete.
• Fully designed with Kotlin in mind, making the code idiomatic and completely type-safe.
• Mappie is easy to use and infers as much as possible.
• Flawless compatibility with other platforms, such as Java types.
• Error messages are informative and suggest concrete actions.

Visit the project documentation for more in-depth information.

Example

The following snippet provides a minimal peek into the idiomatic style of Mappie. Suppose we have the data class Person which we want to map to the data class PersonDto

data class Person(
    val name: String, 
    val surname: String,
    val age: Int,
)

data class PersonDto(
    val name: String, 
    val age: Int, 
)

We can achieve generating such a mapper using the following object mapper.

object PersonToPersonDtoMapper : ObjectMappie<Person, PersonDto>() {
    override fun map(from: Person) = mapping {
        to::name fromValue "${from.name} ${from.surname}"
    }
}

Usage

Mappie can be used via Gradle and Maven.

Gradle

Mappie can be used via Gradle, it can be applied by adding the following snippet to your build.gradle.kts file.

plugins {
    id("tech.mappie.plugin") version "version"
}

For more details, visit the gradle setup documentation.

Maven

Mappie can be used via Maven, it can be applied by adding the following snippet to your pom.xml file.

...
<plugin>
    <groupId>org.jetbrains.kotlin</groupId>
    <artifactId>kotlin-maven-plugin</artifactId>
    <version>...</version>

    <configuration>
        <compilerPlugins>
            <compilerPlugin>mappie</compilerPlugin>
        </compilerPlugins>
        <pluginOptions>
            ...
        </pluginOptions>
    </configuration>
    <dependencies>
        <dependency>
            <groupId>tech.mappie</groupId>
            <artifactId>mappie-maven-plugin</artifactId>
            <version>version</version>
        </dependency>
    </dependencies>
</plugin>
...

We must also add the mappie-api dependency. For example, for the JVM

<dependency>
    <groupId>tech.mappie</groupId>
    <artifactId>mappie-api-jvm</artifactId>
    <version>version</version>
</dependency>

For more details, visit the maven setup documentation.