How to do URL decoding in Java?

Question

In Java, I want to convert this:

https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest_type

To this:

https://mywebsite/docs/english/site/mybook.do&request_type

This is what I have so far:

class StringUTF 
{
    public static void main(String[] args) 
    {
        try{
            String url = 
               "https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do" +
               "%3Frequest_type%3D%26type%3Dprivate";

            System.out.println(url+"Hello World!------->" +
                new String(url.getBytes("UTF-8"),"ASCII"));
        }
        catch(Exception E){
        }
    }
}

But it doesn't work right. What are these %3A and %2F formats called and how do I convert them?

Answer 1

import java.io.UnsupportedEncodingException;
import java.net.URISyntaxException;

public class URLDecoding { 

    String decoded = "";

    public String decodeMethod(String url) throws UnsupportedEncodingException
    {
        decoded = java.net.URLDecoder.decode(url, "UTF-8"); 
        return  decoded;
//"You should use java.net.URI to do this, as the URLDecoder class does x-www-form-urlencoded decoding which is wrong (despite the name, it's for form data)."
    }

    public String getPathMethod(String url) throws URISyntaxException 
    {
        decoded = new java.net.URI(url).getPath();  
        return  decoded; 
    }

    public static void main(String[] args) throws UnsupportedEncodingException, URISyntaxException 
    {
        System.out.println(" Here is your Decoded url with decode method : "+ new URLDecoding().decodeMethod("https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest_type")); 
        System.out.println("Here is your Decoded url with getPath method : "+ new URLDecoding().getPathMethod("https%3A%2F%2Fmywebsite%2Fdocs%2Fenglish%2Fsite%2Fmybook.do%3Frequest")); 

    } 

}

You can select your method wisely :)

Answer 2

This does not have anything to do with character encodings such as UTF-8 or ASCII. The string you have there is URL encoded. This kind of encoding is something entirely different than character encoding.

Try something like this:

String result = java.net.URLDecoder.decode(url, "UTF-8");

Note that a character encoding (such as UTF-8 or ASCII) is what determines the mapping of characters to raw bytes. For a good intro to character encodings, see this article.

Answer 3

I use apache commons

String decodedUrl = new URLCodec().decode(url);

The default charset is UTF-8

Answer 4

Just using URLDecoder.decode once won't be enough .

For example :

Because the same URL can be encoded multiple times, we need to decode it until the URL cannnot be decoded further. For example, "video%252Fmp4" is the result of two encodings. Upon decoding it once, we get "video%2Fmp4". Now the URL needs to be further decoded so that we get "video/mp4", which is the result.

Here is the code that works for all such cases :

public static String decode(String url)  
      {  
                try {  
                     String prevURL="";  
                     String decodeURL=url;  
                     while(!prevURL.equals(decodeURL))  
                     {  
                          prevURL=decodeURL;  
                          decodeURL=URLDecoder.decode( decodeURL, "UTF-8" );  
                     }  
                     return decodeURL;  
                } catch (UnsupportedEncodingException e) {  
                     return "Issue while decoding" +e.getMessage();  
                }  
      }

Answer 5

%3A and %2F are URL encoded characters. Use this java code to convert them back into : and /

String decoded = java.net.URLDecoder.decode(url, "UTF-8");

Answer 6

 try {
        String result = URLDecoder.decode(urlString, "UTF-8");
    } catch (UnsupportedEncodingException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }