How to Fix IntelliJ Annotation Processing — Lombok and MapStruct Issues

In this tutorial, you'll learn about How to Fix IntelliJ Annotation Processing. We cover key concepts, practical examples, and best practices.

The Problem

Annotation processors like Lombok and MapStruct are not working:

@Data  // Lombok annotation — not generating getters/setters
public class User {
    private String name;
}

Calling user.getName() shows "Cannot resolve symbol".

Quick Fix

Step 1: Enable annotation processing

File > Settings > Build, Execution, Deployment > Compiler > Annotation Processors

Check Enable annotation processing.

Step 2: Configure annotation processor

For Maven, the processor is auto-detected from the POM. For IntelliJ project:

Add the processor class:

Annotation Processors > Processor path: [project directory]/lib

Or use the classpath:

Annotation Processors > Obtain processors from project classpath

Step 3: Install the Lombok plugin for IntelliJ

File > Settings > Plugins > Marketplace > Search "Lombok" > Install

Then restart IntelliJ.

Step 4: Enable Lombok annotation processing

File > Settings > Build, Execution, Deployment > Compiler > Annotation Processors

Enable annotation processing and add:

Processors: lombok.launch.AnnotationProcessorHider$AnnotationProcessor

Step 5: Add Maven/Gradle dependencies

For Maven (pom.xml):

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <scope>provided</scope>
</dependency>

For MapStruct:

<dependency>
    <groupId>org.mapstruct</groupId>
    <artifactId>mapstruct-processor</artifactId>
    <scope>provided</scope>
</dependency>

Prevention

• Enable annotation processing before adding Lombok or MapStruct.
• Install the Lombok plugin from the JetBrains Marketplace.
• Keep annotation processor versions aligned with your build tool.

Common Mistakes with annotation processing

1. Forgetting deriving (Show, Eq) on custom data types needed for debugging
2. Placing the wildcard pattern first in case expressions, making all subsequent patterns unreachable
3. Using head and tail instead of pattern matching, causing runtime errors on empty lists

These mistakes appear frequently in real-world INTELLIJ code. DodaTech's contributors have identified these patterns through analysis of open-source projects and production systems.

Practice Exercise

Write a pure function that safely divides two integers using Maybe, then test it with edge cases like division by zero and negative numbers.

This exercise reinforces the concepts covered in this guide. Try implementing it before checking online solutions.

FAQ