buildship-annotation-processing

This is an example of a working annotation processing with a Gradle build on Eclipse and VSCode.

Background

I have a project which requires Lombok and Mapstruct. Both leverages Gradle's annotationProcessor. I also was using Spring Boot which demostrated more issues with this. Using IntelliJ IDEA I am able to import a project leveraging this without any issues. However, the same could not be said with Eclipse and VSCode.

Upon running a Java main or test class, Spring produce the following error:

***************************
APPLICATION FAILED TO START
***************************

Description:

Parameter 0 of constructor in com.pattycake.example.MyApplication required a bean of type 'com.pattycake.example.core.BuildingMapper' that could not be found.

VSCode uses Buildship is used under the hood according to vscode-java issue 1039. Buildship has open issue 329 to support annotation processing. This explains why Eclipse and VSCode demostrated the same behavior.

Work around

I've added the following to build.gradle.

plugins {
  id "com.diffplug.eclipse.apt" version "3.30.0"
}

subprojects {
    apply plugin: 'com.diffplug.eclipse.apt'

    eclipse {
        classpath {
            file.beforeMerged { cp ->
                cp.entries.add( new org.gradle.plugins.ide.eclipse.model.SourceFolder('.apt_generated', null) )
            }
        }
    }
}

Then run

gradlew eclipseJdtApt eclipseFactorypath eclipseJdt

In Eclipse, I imported the project as a Gradle project. In VSCode, I open the folder into a new window.