JAVA EXAMPLE PROGRAMS

JAVA EXAMPLE PROGRAMS

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How to assign default values to custom annotations?


Description:

  • We can assign default values to annotation members. These values will be return incase if you didn't provide any values to the annotation members.
  • We can assign default values by using default clause during members declarations. Make sure that the default values are same type as members.
  • Below example shows how to assign default vlaues to annotation members.


Code:
package com.java2novice.annotations;

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


@Retention(RetentionPolicy.RUNTIME)
@interface MyAnnot{
	
	String key() default "site";
	String value() default "java2novice.com";
}

public class MyAnnotDefaultValues {

	@MyAnnot()
	public void myAnnotationTestMethod(){
		
		try {
			Class<? extends MyAnnotDefaultValues> cls = this.getClass();
			Method mth = cls.getMethod("myAnnotationTestMethod");
			MyAnnot myAnno = mth.getAnnotation(MyAnnot.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[]){
		
		MyAnnotDefaultValues mat = new MyAnnotDefaultValues();
		mat.myAnnotationTestMethod();
	}
}

Output:
key: site
value: java2novice.com
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Knowledge Centre
doPost Vs doGet methods
doGet() method is used to get information, while doPost() method is used for posting information. doGet() requests can't send large amount of information and is limited to 240-255 characters. However, doPost()requests passes all of its data, of unlimited length. A doGet() request is appended to the request URL in a query string and this allows the exchange is visible to the client, whereas a doPost() request passes directly over the socket connection as part of its HTTP request body and the exchange are invisible to the client.
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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].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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