Develop Reference

Java annotations logic implementation

I'm creating a java library that can be imported in multiple projects and creates a graphQL schema file with classes and queries annotated with my custom annotations.
I want that when I compile the project, the classes marked by the annotation will be added (with all their fields) into a file that will be the "schema.graphqls" file.
My question is: where I have to insert my logic implementation? Creating a method into the annotation class?
I created two custom annotations, as in the following files:
package annotations;
import java.lang.annotation.*;
#Documented
#Retention(RetentionPolicy.SOURCE)
#Target(ElementType.TYPE) //with TYPE, you can annotate class, interfaces, annotation, types or enum
public #interface GraphQLQuery {
}
GraphQLQuery.java
package annotations;
import java.lang.annotation.*;
#Documented
#Retention(RetentionPolicy.SOURCE)
#Target(ElementType.TYPE) //with TYPE, you can annotate class, interfaces, annotation, types or enum
public #interface GraphQLModel {
}
GraphQLModel.java

Quarkus tests inheritance not allowed?

Moving some common annotations from a test class to a base one just doesn't work in Quarkus, is this intended or I'm missing something?
This works:
#QuarkusTest
#TestProfile(FunctionalTestProfile.class)
class FrontendControllerTest {...}
This doesn't work:
#QuarkusTest
#TestProfile(FunctionalTestProfile.class)
public class BaseFunctionalTest {}
class FrontendControllerTest extends BaseFunctionalTest {...}
Annotations just don't get applied to child classes

The #QuarkusTest and #TestProfile annotations are not declared #Inherited, so this should not be expected to work.

Converting package level Java annotation to Kotlin

Is it possible to convert a package level Java annotation to Kotlin?
Java annotation (MyAnnotation.java):
package com.myexample.annotation;
#Retention(RUNTIME) #Target(PACKAGE)
public #interface MyAnnotation {
}
Application of annotation (package-info.java)
#MyAnnotation
package com.myexample
The following does not seem to work (although it does compile) - my annotation processor does not detected any of the classes in the package com.myexample:
MyAnnotation.kt
package com.myexample.annotation
#Target(allowedTargets = [AnnotationTarget.CLASS, AnnotationTarget.FILE])
#Retention(AnnotationRetention.SOURCE)
annotation class MyAnnotation
package-info.kt
#file:MyAnnotation
package com.myexample
import com.myexample.annotation.MyAnnotation

No, it's not currently possible. You can simply leave package-info.java as a Java file.

How annotation internally works in java

I know how to create custom annotation. But i am unable to understand how does it work internally. If i take example of spring annontation.
#PropertySource(value = { "classpath:database.properties" }).
if we see internal details of #PropertySource annotation
#Target({ java.lang.annotation.ElementType.TYPE })
#Retention(RetentionPolicy.RUNTIME)
#Documented
#Repeatable(PropertySources.class)
public #interface PropertySource {
public abstract String name();
public abstract String[] value();
public abstract boolean ignoreResourceNotFound();
}
We do not have provided any implementation here for loading property file.
Then How is it loading property file from classpath. Who is working behind the scene ?

Really simple: framework. That is. All 'custom' annotations processed by frameworks using reflection. Only small scope of annotations are processed by compiler, such as #Override, #SuppressWarnings, #Retention and so on

Can't get #Component to be inherited in Spring?

In my project there's a common base class that all client classes extend. This has an #Autowired field that needs to be injected by Hibernate. These are all grouped together in another class that has an #Autowired collection of the base class.
In order to reduce boilerplate for client code I'm trying to get #Component inherited. With #Component not doing this by default (apparently it used to though), I created this workaround annotation
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
#Component
#Inherited
public #interface InheritedComponent {
}
... and annotated the base class with it. Its not pretty but I hoped it would work. Unfortunately it didn't, which really confuses me as #Inherited should make it work
Is there any other way to get #Component inherited? Or do I just have to say that any class that extends the base class needs this boilerplate?

The problem is that the Component annotation type itself needs to be marked with #Inherited.
Your #InheritedComponent annotation type is correctly inherited by any classes that extend a superclass which is marked with #InheritedComponent - but it does not inherit #Component. This is because you have #Component on the annotation, not the parent type.
An example:
public class InheritedAnnotationTest {
#InheritedComponent
public static class BaseComponent {
}
public static class SubClass extends BaseComponent {
}
public static void main(String[] args) {
SubClass s = new SubClass();
for (Annotation a : s.getClass().getAnnotations()) {
System.out.printf("%s has annotation %s\n", s.getClass(), a);
}
}
}
Output:
class brown.annotations.InheritedAnnotationTest$SubClass has annotation #brown.annotations.InheritedComponent()
In other words, when resolving what annotations a class has, the annotations of the annotations are not resolved - they do not apply to the class, only the annotation (if that makes sense).

I've dealt with this issue by creating my own annotation (heritable) and then customizing classpath scanning:
#Target(ElementType.TYPE)
#Retention(RetentionPolicy.RUNTIME)
#Component
#Inherited
public #interface BusinessService {
}
Spring configuration look likes this:
<context:component-scan base-package="io.bar">
<context:include-filter type="annotation"
expression="io.bar.core.annotations.BusinessService" />
</context:component-scan>
from Spring doc 5.10.3 Using filters to customize scanning