CODEWITHSUNDEEP
javareflection
cat916
cat916

Reputation: 1361

Java reflection derived class

This is my scenario "I have a abstract class. There are many derived classed extending this abstract class with the use of annotations. In addition, I have a method of abstract class, that was reflected all notations in one particular derived class". 

// Here's a definition of annotation
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface SampleAnnotation {
   int sample();
}

public abstract class A { 

 // Here's a method to reflect all annotations
 // in particular derived class like B or C
 @Override
 public void foo() {

 }}

public class B extends A {
  @SampleAnnotation (sample = 1)
  public void step1() {}

  @SampleAnnotation (sample = 2)
  public void step2() {}

}

public class C extends A {
  @SampleAnnotation (sample = 1)
  public void step1() {}

  @Sample (stage = 2)
  public void step2() {}
}

How can I use java reflection to reflect all the annotations in specific derived class like B or C ?

Upvotes: 3

Views: 1325

Answers (2)

Konrad Reiche
Konrad Reiche

Reputation: 29493

It depends:

  1. Do you want to get all method annotations of a concrete class
  2. Do you want to get all method annotations of all concrete classes

The first one can be achieved with a method implementation of foo like this:

public void foo() {
     for (Method method : this.getClass().getDeclaredMethods()) {
          for (Annotation a : method.getAnnotations()) {
              // do something with a
          }
     }
}

Then you can invoke foo from your concrete class, for instance:

new B().foo();

For the second case you will need to do class path scanning as Peter Lawrey has pointed out.

Upvotes: 1

Peter Lawrey
Peter Lawrey

Reputation: 533492

Perhaps what you have in mind is this Reflections library.

Using Reflections you can query your metadata such as:

  • get all subtypes of some type
  • get all types/methods/fields annotated with some annotation, w/o annotation parameters matching
  • get all resources matching matching a regular expression

Upvotes: 3

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