visitfilter.java

一本jsp自学教材

package test;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.*;
import java.util.Date;

public final class VisitFilter implements Filter
 {
   private FilterConfig filterConfig = null;
   private String CharSetting="";
   public void init(FilterConfig filterConfig) throws ServletException
    {
	this.filterConfig = filterConfig;
        //获取初始化参数
        this.CharSetting = filterConfig.getInitParameter("CharSetting");
    }   
    public void doFilter(ServletRequest request, 
                         ServletResponse response,
                         FilterChain chain)
	throws IOException, ServletException 
    {
         HttpServletRequest req=(HttpServletRequest)request;
        //对请求重新编码
	req.setCharacterEncoding(CharSetting);	
        Date date=new Date();
        String datetime=date.toLocaleString();
        //向日志文件写入访问信息	
	filterConfig.getServletContext().log
	    (datetime+ "用户访问的URL: "+req.getRequestURL());
        //通过，继续处理。
        chain.doFilter(request,response);
    }
    public void destroy() 
    {
        this.CharSetting = null;
        this.filterConfig = null;
    }
}