How do I obtaion annotations at runtime using reflection?

This example demonstrate how to obtaion annotations of a class and methods. We use the reflection API to get class and method information from where we can read information about annotation attached to the class or the method.

package org.kodejava.example.annotation;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

@HelloAnno(value = "Hello", greetTo = "Universe")
public class GettingAnnotation {
    public static void main(String[] args) {
        GettingAnnotation demo = new GettingAnnotation();

        Class clazz = demo.getClass();
        Annotation[] annotations = clazz.getAnnotations();
        for (Annotation anno : annotations) {
            System.out.println("Annotation Type: " + anno.annotationType());
        }

        HelloAnno anno = (HelloAnno) clazz.getAnnotation(HelloAnno.class);
        System.out.println("Anno Value  : " + anno.value());
        System.out.println("Anno GreetTo: " + anno.greetTo());

        try {
            Method m = clazz.getMethod("sayHi");

            anno = m.getAnnotation(HelloAnno.class);
            System.out.println("Anno Value  : " + anno.value());
            System.out.println("Anno GreetTo: " + anno.greetTo());
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }

        demo.sayHello();
    }

    @HelloAnno(value = "Hi", greetTo = "Alice")
    public void sayHi() {
    }

    @HelloAnno(value = "Hello", greetTo = "Bob")
    public void sayHello() {
        try {
            Method m = getClass().getMethod("sayHello");
            HelloAnno anno = m.getAnnotation(HelloAnno.class);

            System.out.println(anno.value() + " " + anno.greetTo());
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }
    }
}

You can find the HelloAnno annotation that we use above on the following example: How do I create a simple annotation?.

The result of our program is:

Annotation Type: interface org.kodejava.example.annotation.HelloAnno
Anno Value  : Hello
Anno GreetTo: Universe
Anno Value  : Hi
Anno GreetTo: Alice
Hello Bob

Wayan Saryada

Programmer, runner, recreational diver, currently living in the island of Bali, Indonesia. Mostly programming in Java, creating web based application with Spring Framework, Hibernate / JPA.

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