Java: How to Encode or Decode URL String Or Form Parameter

In Java Examples, when using the GET method, parameter names and their values get submitted on the URL string after a question mark. Different parameter name/value pairs are separated by ampersands.

Usually, parameters are accessed from a request in an already decoded format (via request.getParameter()), so no decoding is necessary.

However, occasionally certain situations arise where you need to decode a string that has been URL encoded (for instance, by the URLEncoder.encode(String s, String encoding) method or the javascript escape() function).

Java code:

package crunchify.com.tutorials;

import java.net.URLDecoder;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

/**
 * @author crunchify.com
 * 
 */

public class CrunchifyEncodeDecodeExample {

	public static void main(String[] args) throws Exception {

		String crunchifyValue1 = "This is a simple Example from Crunchify";
		
		// Use StandardCharsets
		String ecodedValue1 = URLEncoder.encode(crunchifyValue1, StandardCharsets.UTF_8.name());
		String decodedValue1 = URLDecoder.decode(ecodedValue1, StandardCharsets.UTF_8.name());
		System.out.println("crunchifyValue1 after encoding => " + ecodedValue1);
		System.out.println("crunchifyValue1 after decoding (Original Value): => " + decodedValue1);

		String crunchifyValue2 = "Hello There, We started accepting Guest-Posts on Crunchify...";
		
		// Or directly provide UTF-8 
		String encodedValue2 = URLEncoder.encode(crunchifyValue2, "UTF-8");
		String decodedValue2 = URLDecoder.decode(encodedValue2, "UTF-8");
		System.out.println("\ncrunchifyValue2 after encoding => " + encodedValue2);
		System.out.println("crunchifyValue2 after decoding (Original Value) => " + decodedValue2);

	}
}

Other must read:

• Java Tutorial: How to Create RESTful Java Client using Apache HttpClient – Example
• How to use AJAX, jQuery in Spring Web MVC (.jsp) – Example

Console Output:

crunchifyValue1 after encoding => This+is+a+simple+Example+from+Crunchify
crunchifyValue1 after decoding (Original Value): => This is a simple Example from Crunchify

crunchifyValue2 after encoding => Hello+There%2C+We+started+accepting+Guest-Posts+on+Crunchify...
crunchifyValue2 after decoding (Original Value) => Hello There, We started accepting Guest-Posts on Crunchify...

URL encoding is required much more often than URL decoding, since decoding usually takes place automatically during calls the request.getParameter().

However, it is good to know that URLDecoder.decode() exists for the occasional situation where it is needed.