import  java.io.IOException;
import  java.util.ArrayList;
import  java.util.Random;

import  javax.servlet.ServletException;
import  javax.servlet.http.HttpServlet;
import  javax.servlet.http.HttpServletRequest;
import  javax.servlet.http.HttpServletResponse;

import  net.sf.json.JSONSerializer;


public   class  TagCloudAction  extends  HttpServlet  {


     private   static  String cache  =   "" ;
     /** */ /**
     * 
      */
     private   static   final   long  serialVersionUID  =   - 7031695721764039045L ;

    @Override
     protected   void  doGet(HttpServletRequest req, HttpServletResponse resp)
             throws  ServletException, IOException  {
        resp.setHeader(  " Pragma " ,  " no-cache "  );
        resp.addHeader(  " Cache-Control " ,  " must-revalidate "  );
        resp.addHeader(  " Cache-Control " ,  " no-cache "  );
        resp.addHeader(  " Cache-Control " ,  " no-store "  );
        resp.setDateHeader( " Expires " ,  0 );
        resp.setContentType( " text/xml " );
        resp.setCharacterEncoding( " UTF-8 " );
         if (cache.isEmpty())
         {
            cache  =  getTagCloudJSONString();
        }
        resp.getOutputStream().write(cache.getBytes( " UTF-8 " ));
        resp.flushBuffer();
    }
    
     private  String getTagCloudJSONString()
     {
        Category c  =   new  Category( " Name " , " This is comments " , 10 );
        c.setCategoryID( 10 );
         // System.out.println( JSONSerializer.toJSON(c).toString() );
         // System.out.println( JSONSerializer.toJSON(c).toString(2) );
        
        ArrayList < Category >  categoriesList  =   new  ArrayList < Category > ();
        Random r  =   new  Random();
        String[] tags  =   new  String[] {
                 " JAVA " , " Groovy " , " Servlet " , " J2EE " , " JSP " , " J2SE "
                , " JSON " , " AJAX " , " CaiClient " , " .NET " , " C# " , " Perl " ,
                 " Python " , " Rails " , " Ruby " , " Boss " , " Nokia " , " GPhone " , " iPhone "
                , " HiPhone " , " Ericsson " , " Semens " , " Novels " , " 春天 " , " 夏天 " , " 秋天 " , " 冬天 " , " 节日快乐 " ,
                 " 破釜沉舟 " , " 瑞星杀毒 " , " 奶粉事故 "
                , " 奥运会 " , " Grails " , " Google " , " Baidu " , " XiaoNei " ,
                 " 开心网 " , " 校内网 " , " 海内网 " , " 都是垃圾 " , " 萨达姆 " , " PK " , " 网摘 "
        } ;
         int  len  =  tags.length - 1 ;
         for  ( int  i  =   0 ; i  <   100 ; i ++ )  {
            Category item  =   new  Category(tags[r.nextInt(len)], " This is comments for  " + i,r.nextInt( 100 ));
            item.setCategoryID(i);
            categoriesList.add(item);
        }
        
        System.err.println( JSONSerializer.toJSON(categoriesList).toString() );
         // System.err.println( JSONSerializer.toJSON(categoriesList).toString(2) );
        
         return  JSONSerializer.toJSON(categoriesList).toString( 2 );
    }

}

<! DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd" >
< html >
< head >
< meta  http-equiv ="Content-Type"  content ="text/html; charset=UTF-8" >
< title > Tag Cloud </ title >
< script  type ="text/javascript"  src ="json2.js" ></ script >
< script  type ="text/javascript"  src ="tagcloud.js" ></ script >
< link  rel =StyleSheet  type ="text/css"  href ="tagCloud.css" >
</ head >
< body >
< p > Version.1 use raw XMLHttpRequest to get JSON data from a Servlet. </ p >
< input  id ="btn_getTagCloud1"  type ="button"  value ="Get tag cloud style1"
    onclick ="getTagCloud();"   />
< div  id ="tagcloud" ></ div >

< input  id ="btn_getTagCloud2"  type ="button"  value ="Get tag cloud style2"
    onclick ="getTagCloud2();"   />
< div  id ="tagcloudwithstyle2" ></ div >
</ body >
</ html >