JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

Publish Your Article Here

How to get annotations at runtime using java reflection?


Description:

  • Incase if any annotation is specifies its retention policy as RUNTIME, then those annotations can be queried at runtime by any java program.
  • Below example code shows how to query an annotation values during runtime using java reflection.


Code:
package com.java2novice.annotations;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Method;

@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnotation{
	
	String key();
	String value();
}

public class MyAnnotationTest {

	@MyAnnotation(key="site", value="java2novice.com")
	public void myAnnotationTestMethod(){
		
		try {
			Class<? extends MyAnnotationTest> cls = this.getClass();
			Method mth = cls.getMethod("myAnnotationTestMethod");
			MyAnnotation myAnno = mth.getAnnotation(MyAnnotation.class);
			System.out.println("key: "+myAnno.key());
			System.out.println("value: "+myAnno.value());
		} catch (SecurityException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (NoSuchMethodException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public static void main(String a[]){
		
		MyAnnotationTest mat = new MyAnnotationTest();
		mat.myAnnotationTestMethod();
	}
}

Output:
key: site
value: java2novice.com
<< Previous Program | Next Program >>

List Of All Annotation (Metadata) Programs:

  1. How to create basic custom annotation?
  2. What is Retention policy in java annotations?
  3. How to get annotations at runtime using java reflection?
  4. How to get all annotations from a class?
  5. How to assign default values to custom annotations?
  6. What is marker annotation and how to process it at runtime?
  7. Built-in Java Annotations: @Deprecated example
  8. Built-in Java Annotations: @Override example
  9. Built-in Java Annotations: @SuppressWarnings example
  10. What is single member annotation and how to process it?
Knowledge Centre
String Vs StringBuffer
We know that String is immutable object. We can not change the value of a String object once it is initiated. If we try to change the value of the existing String object then it creates new object rather than changing the value of the existing object. So incase, we are going to do more modificatios on String, then use StringBuffer. StringBuffer updates the existing objects value, rather creating new object.
Famous Quotations
Never argue with a fool, onlookers may not be able to tell the difference.
-- Mark Twain

About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

Most Visited Pages

Other Interesting Sites

Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
Privacy Policy | Copyright © 2022 by Nataraja Gootooru. All Rights Reserved.