The all-open plugin for Gradle can be used as follows:

buildscript {
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-allopen:$kotlin_version"
    }
}
apply plugin: "kotlin-allopen"

We have to add the plugin artifact in the buildscript dependencies section of the Gradle file. We can also enable the all-open plugin using the plugins section, as follows:

plugins {
   id "org.jetbrains.kotlin.plugin.allopen" version "1.2.41"
 }

Following this, we can specify a list of annotations that will make our classes open and accessible:

allOpen {
    annotation("javax.ejb.Stateless")
 } 

We can specify multiple annotations using the annotations section in the allOpen plugin:

 allOpen {
     annotations("javax.ejb.Stateless",
     "javax.inject.Inject")
 }

We can then define custom annotations. The all-open compiler plugin is used to open the classes that are annotated with the custom annotations:

allOpen {
    annotation("org.rao.kotlin.javaee.Annotation")
}


@org.rao.kolin.javaee.Annotation
annotation class MyAnnotation

@MyAnnotation
class  Person{ }

Now, the Person class will be open.

The MyAnnotation class is annotated with a meta-annotation—@org.rao.kolin.javaee.Annotation. It is now an all-open plugin annotation that can be used in other classes to make them open and accessible.