When surfing the internet and casually viewing the source of your favourite sites [as you do :) ] you may notice some CSS links with query strings.

<link rel="stylesheet" href="sources/css/basic.css?pr=452343223" type="text/css" media="all" />

This may seem pretty pointless as the webserver will ignore any parameters and continue to read the CSS file's contents as normal.

So what is the purpose of the query string on a CSS link?

It's actually a pretty simple hack. If you change the query string every time the style sheet is changed it will force the client's browser to reload the CSS file from the server - removing the possibility of the client using an out of date cached version. This then ensures that the webpage is rendered with the most up to date CSS after each release.

The tutorial also provides some examples of CSS, HTML & googles Gson Jar files that convert Java Objects into their JSON representation. Making it easy for Javascript to parse the response data.

Obviously I would not recommend using this word for word in production as I did not include XSS security such as striping tags and escaping output. Here is a great XSS cheat sheet from OWASP.

import java.util.Map;
import java.util.TreeMap;

/**
 * 
Simple first level JavaScript Object Notation Map converter
 * 
http://www.philipstarritt.com
 * @version 1.0
 * @author Philip Starritt
 * @since 2013/04/15 22:25
 */
public class JavaSon {

	/**
	 * 
Will convert a Java Map into JSON format that can be easily used in AJAX calls.
	 * 
String, Integer & Boolean will be printed in JSON expected format.
	 * 
Other objects (Arrays/Lists/Objects etc) will .toString() so it's best to override.
	 * 
This method can be further extended to include nested arrays & Objects in the 
     *    JavaScript Object Notation.
	 * @param map
	 * @return String in JSON  
	 */
	public static String toJson(Map map){
		return (map != null && !map.isEmpty()) ? parse(map) : null;
	}

	private static String parse(Map map) {
		int counter = 0;
		StringBuilder stringBuilder = new StringBuilder("{\n");
		for (Map.Entry mapEntry : map.entrySet()) {
		    stringBuilder.append("\t\"" + mapEntry.getKey() + "\":");
		    String className = mapEntry.getValue().getClass().getSimpleName();
		    if(className.equals(Boolean.class.getSimpleName()) ||
		       className.equals(Integer.class.getSimpleName())){
		    	stringBuilder.append("" + mapEntry.getValue() + "");
		    }
		    else{
		    	stringBuilder.append("\"" + mapEntry.getValue() + "\"");
		    }
			if((map.size() - counter) != 1){
				stringBuilder.append(",\n");
			}
			counter++;
		}
		return stringBuilder.append("\n}").toString();
	}
	
	/**
	 * 
Main
	 */
	public static void main(String...args){
		Map  map = new TreeMap();
		map.put("1 - first", 2);
		map.put("2 - second", "dfdf");
		map.put("3 - third", true);
		map.put("last", new Integer(4));
		System.out.println(JavaSon.toJson(map));
		
		/*
		 * OUTPUT 
		 * 
		 * 	{
		 *		"1 - first":2,
		 *		"2 - second":"dfdf",
		 *		"3 - third":true,
		 * 		"last":4
		 *	}
		 * 
		 */
	}
}

On Thursday I will add a another code example on how to use jQuery/Javascript AJAX calls on a Java servlet and access the JSON formatted response data.

cya!

I hope this comes in handy for someone.

public static int divide(int a, int b){  
    	if(b == 0){
            return 0;
    	}
    	else if(a < b){
            return 0;
    	}
        else if(b == 1){
            return a;
        }
    	else{
            return add(1, divide(sub(a,b),b));
    	}
}