refererfilter.java

这个weblogging 设计得比较精巧

package org.roller.presentation.filters;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.roller.model.RefererManager;
import org.roller.presentation.RollerContext;
import org.roller.presentation.RollerRequest;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;



/**
 * Keep track of referers.
 * 
 * @web.filter name="RefererFilter"
 * *web.filter-mapping url-pattern="/page/*"
 * 
 * @author David M. Johnson
 */
public class RefererFilter implements Filter
{
    private FilterConfig   mFilterConfig = null;
    private static Log mLogger = 
        LogFactory.getFactory().getInstance(RefererFilter.class);
   
    /**
     * destroy
     */
    public void destroy()
    {
    }

    /**
     * doFilter
     */
    public void doFilter(
        ServletRequest req, ServletResponse res, FilterChain chain)
        throws IOException, ServletException
    {
        HttpServletRequest request = (HttpServletRequest)req;
        boolean isRefSpammer = false;       
        try
        {
            RollerRequest rreq = RollerRequest.getRollerRequest(request);
            RollerContext rctx = RollerContext.getRollerContext(
                mFilterConfig.getServletContext());
            
            if ( rreq.getUser() != null )
            {
                String userName = rreq.getUser().getUserName();                
                
                // Base page URLs, with and without www.
                String basePageUrlWWW = 
                    rctx.getAbsoluteContextUrl(request)+"/page/"+userName;                        
                String basePageUrl = basePageUrlWWW;          
                if ( basePageUrlWWW.startsWith("http://www.") )
                {
                    // chop off the http://www.
                    basePageUrl = "http://"+basePageUrlWWW.substring(11);
                }
                                 
                // Base comment URLs, with and without www.  
                String baseCommentsUrlWWW = 
                    rctx.getAbsoluteContextUrl(request)+"/comments/"+userName;   
                String baseCommentsUrl = baseCommentsUrlWWW;          
                if ( baseCommentsUrlWWW.startsWith("http://www.") )
                {
                    // chop off the http://www.
                    baseCommentsUrl= "http://"+baseCommentsUrlWWW.substring(11);
                }
                
                // Don't process hits from same user's blogs as referers by
                // ignoring Don't process referer from pages that start with base URLs. 
                String referer = request.getHeader("Referer");               
                if (  referer==null ||
                      ( 
                         !referer.startsWith( basePageUrl ) 
                      && !referer.startsWith( basePageUrlWWW )
                      && !referer.startsWith( baseCommentsUrl )
                      && !referer.startsWith( baseCommentsUrlWWW )
                      )
                   )
                {
                    RefererManager refMgr = 
                        rreq.getRoller().getRefererManager();
                    isRefSpammer = refMgr.processRequest(rreq);
                }
                else
                {
                    if (mLogger.isDebugEnabled())
                    {
                        mLogger.debug("Ignoring referer="+referer);
                    }
                }
            }
        }
        catch (Exception e)
        {
            mLogger.error("Processing referer",e);
        }
        
        if (isRefSpammer)
        {
            HttpServletResponse response = (HttpServletResponse)res;
            response.sendError(HttpServletResponse.SC_FORBIDDEN);            
        }
        else
        {
            chain.doFilter(req, res);
        }
    }

    /**
     * init
     */
    public void init(FilterConfig filterConfig) throws ServletException
    {
        mFilterConfig = filterConfig;
    }
}