package shopcart.servlets;import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.http.*;import shopcart.servlets.*;import DebugLog;public class AdLinkRotatorServlet extends GenericServlet implements SingleThreadModel{	protected Vector ads;	protected int curIndex;	protected String imageURL;	protected DebugLog logger;		public void init(ServletConfig config) throws ServletException	{		String imageDirName;		String logServer;		File imageDir=null;		File adSpec=null;				super.init(config);				curIndex = 0;		ads = new Vector();		imageDirName = getInitParameter("imagedir");		imageURL = getInitParameter("imageroot");		logServer = getInitParameter("logserver");				logger = new DebugLog();		logger.logTo(logServer);				try		{    		if(imageDirName != null) imageDir = new File(imageDirName);	    		if(imageDir != null) adSpec = new File(imageDir,"ads.txt");	    		logger.log("Looking for adspec at: "+adSpec);	    		//Try to load the ads from a specification file    		if((adSpec != null)&& adSpec.exists())    		{    		    try    		    {        		    FileReader fileIn = new FileReader(adSpec);        		    BufferedReader bufIn = new BufferedReader(fileIn);    		        String curLine;    		        int index;    		        String link,fileName;    		        AdFileEntry newEntry;	            		        while((curLine = bufIn.readLine()) != null)    		        {    		            index = curLine.indexOf(" ");	                		            if(index > 0)    		            {    		                link = curLine.substring(0,index);    		                fileName = curLine.substring(index+1);	                    		                newEntry = new AdFileEntry(link,fileName);	                    		                ads.addElement(newEntry);    		            }    		        }	            		    bufIn.close();    		    }    		    catch(Exception exp)    		    {    		        logger.log("Invalid ad spec. file.");    		        ads.removeAllElements();    		    }    		}		    		//If no spec file, or a bad one, just show ads    		if((ads.size()==0)    		    && (imageDir!=null)     		    && imageDir.exists()     		    && imageDir.isDirectory())    		{        		String[] files;        		int i,max;    		    			files = imageDir.list();			    			max = files.length;			    			for(i=0;i<max;i++)    			{    				ads.addElement(new AdFileEntry(null,files[i]));    			}    		}    		else if(ads.size()==0)    		{    			logger.log("Cannot find image dir: "+imageDirName);    		}		}		catch(Exception exp)		{		    logger.log(exp);		}	}	    public void service(ServletRequest request,						ServletResponse response)						throws IOException,ServletException    {		AdFileEntry curEntry;		PrintWriter out=null;		int len;				try		{    		out = response.getWriter();    		len = ads.size();		    		if(len>0)    		{    			curEntry = (AdFileEntry) ads.elementAt(curIndex);			    			if(curEntry.link != null)    			{    		        out.print("<A HREF=\"");    		        out.print(curEntry.link);    		        out.println("\">");    			}		    		    out.print("<IMG SRC=");    		    out.print(imageURL);    		    out.print("/");    		    out.print(curEntry.fileName);    		    out.println(">");		        		    if(curEntry.link != null)    		    {    		        out.println("</A>");    		    }		    			curIndex= (curIndex+1)%len;        	}        	else        	{        	    //Print a comment to HTML for testing        	    out.println("<!--No ads.-->");        	}    	}    	catch(Exception exp)    	{    	    logger.log(exp);    	}    }}class AdFileEntry{    public String link;    public String fileName;        public AdFileEntry(String l,String file)    {        link = l;        fileName = file;    }}