adlinkrotatorservlet.java

JAVA在线商店带JSP的

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;
    }
}