Mapstruct + Lombok together not compiling: unknown property in result type

java

lombok

mapstruct

annotation-processing

byAnton Shumikhin·Feb 28, 2025

Let's get Lombok and MapStruct in line to avoid those pesky compilation errors. Your mission, if you choose to accept it, is to give your maven-compiler-plugin The Order:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.8.1</version>
            <configuration>
                <annotationProcessorPaths>
                    <!-- Lombok first, because it can't wait -->
                    <path>
                        <groupId>org.projectlombok</groupId>
                        <artifactId>lombok</artifactId>
                        <version>LATEST_LOMBOK_VERSION</version>
                    </path>
                    <!-- Then MapStruct, because it's patient -->
                    <path>
                        <groupId>org.mapstruct</groupId>
                        <artifactId>mapstruct-processor</artifactId>
                        <version>LATEST_MAPSTRUCT_VERSION</version>
                    </path>
                </annotationProcessorPaths>
                <!-- Because we care about compatibility -->
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
    </plugins>
</build>

Don't forget to replace LATEST_LOMBOK_VERSION and LATEST_MAPSTRUCT_VERSION with your current versions. This strategy ensures Lombok's eager code generation finishes before MapStruct—и voilà, no more unknown property errors.

Harmonizing Lombok and MapStruct: Configurations and setups

Maven and Gradle: The dynamic duo

With Maven, you should add the lombok-mapstruct-binding; it's the peace treaty for Lombok version 1.18.16 and above. Who knew it was that easy to solve interoperability issues?

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok-mapstruct-binding</artifactId>
    <version>0.2.0</version>
    <scope>provided</scope> <!-- Because we're generous -->
</dependency>

For those of you who are on team Gradle, here's your playbook:

annotationProcessor 'org.projectlombok:lombok:latest' // First in, first out.
compileOnly 'org.projectlombok:lombok:latest' // Keeps it light.
annotationProcessor 'org.mapstruct:mapstruct-processor:latest' // Patience is a virtue.

Again, replace latest with the latest versions. We don't want you living in the past.

IntelliJ: The master of ceremony

Even IntelliJ has a role to play. Enable its annotation processing by:

Exploring Settings / Preferences.
Treading the path to Build, Execution, Deployment > Compiler > Annotation Processors.
Embracing the Enable annotation processing.

You might have to make sure the source and target are set to Java 8 or your respective version in IntelliJ's settings. An educated IDE equals a smooth compilation process.

Pragmatic guide: Unlocking a seamless integration

Conflict resolution

You may get your hands dirty when smoothing out:

Delombok. Don't create pandemonium by stripping out Lombok annotations before MapStruct can see them.
Rely on @Getter and @Setter when necessary instead of @Data. It minimums magic but puts you on the driver's seat.
Keep @MapperConfig at bay with MapStruct when it cross paths with Lombok.

Under the hood

To play Sherlock, inspect the generated implementations post a clean build:

Check if all Lombok generated methods are in the brigade.
Ensure MapStruct's masterpieces have the desired mappings.

Maven setting

Set your project's source and encoding to UTF-8 to ward off any "lost in translation" issues.

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <!-- because UTF-8 is cufflinks, others are sleeve buttons-->
</properties>