@ConfigurationProperties Spring Boot Configuration Annotation Processor not found in classpath

I had the same problem. I use idea 2017.2 and gradle 4.1, and some blog said you should add:

dependencies {
    optional "org.springframework.boot:spring-boot-configuration-processor"
}

But I changed it to this:

dependencies {
    compile "org.springframework.boot:spring-boot-configuration-processor"
}

And the warning is gone.

According to the Spring Boot docs, the correct configuration since Gradle 4.6 is

dependencies {
    annotationProcessor group: 'org.springframework.boot', name: 'spring-boot-configuration-processor'
    // ...
}

IntelliJ IDEA supports annotationProcessor scope since build 193.3382 (2019.3). Don't forget to enable annotation processing in IntelliJ IDEA settings.

It happens to me for two reasons in IDEA:

1. Double check if your setting is picked (enabled) in IDEA: Preferences->Annotation Processors->Enable annotation processing.
2. After update your Idea, check your plugins and update them. It happens that plugins become incompatible with your new IDEA version, so just click to update them.