MapStruct + Quarkus

This example demonstrates how easy it is to use MapStruct in a Quarkus application.

The example was basically built with the following steps:

1. Create a new Quarkus application

   mvn io.quarkus:quarkus-maven-plugin:1.0.1.Final:create \
     -DprojectGroupId=org.mapstruct.examples.quarkus \
     -DprojectArtifactId=mapstruct-examples-quarkus \
     -DclassName="org.mapstruct.example.quarkus.PersonResource" \
     -Dpath="/person" \
     -Dextensions="resteasy-jsonb"
   

2. Add mapstruct as a dependency

   <dependency>
     <groupId>org.mapstruct</groupId>
     <artifactId>mapstruct</artifactId>
     <version>${org.mapstruct.version}</version>
     <scope>provided</scope>
   </dependency>

3. Add the mapstruct-processor as a regular provided scoped dependency and not as described in the reference guide

   <dependency>
     <groupId>org.mapstruct</groupId>
     <artifactId>mapstruct-processor</artifactId>
     <version>${org.mapstruct.version}</version>
     <scope>provided</scope>
   </dependency>

4. Set CDI as the default component-model (see reference guide)

5. Define a mapper and inject it with @Inject in the service

That's it!

Native images

As MapStruct is not using reflection within the mappers native images are supported as long as CDI is used to retrieve the mappers. Just try to package your Quarkus application in a native image and feel the speed!

mvn package -Dnative

In case you prefer to use Mappers.getMapper(...) be aware that this is not automatically supported by native images. Internally the getMapper method uses reflection to retrieve the mapper implementation. This is the only place where MapStruct uses reflection and thus it causes issues with native images.

There are some workarounds by defining additional metadata used during native image creation by GraalVM. For example you can create a Feature as described here and register all you mapper implementations and their constructor(s).

For example if you just have a PersonMapper the feature might look like this:

@AutomaticFeature
class MapstructMapperFeature implements Feature {
    public void beforeAnalysis(BeforeAnalysisAccess access) {
        try {
            Class<?> mapperClass = Class.forName( "org.mapstruct.example.quarkus.mapper.PersonMapperImpl" );
            RuntimeReflection.register( mapperClass );
            RuntimeReflection.register( mapperClass.getConstructors() );
        }
        catch ( ClassNotFoundException e ) {
            throw new RuntimeException( e );
        }
    }
}

One drawback

When using the Quarkus dev mode the mapper will automatically be (re)generated in case you make change to the @Mapper annotated class. Changing a dependent class (like PersonDto in this example) will not (re)generate the mapper implementation.

As a workaround you can quit the dev-mode, recompile and start the application once again or you can make a (temporary) change to the @Mapper annotated class so that it will be picked up and a valid implementation will be generated.

Pay attention: You have to add the mapstruct-processor as described above and not using the maven-compile-plugin.