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实现一个监听器接口

package com.listers;import javax.servlet.ServletContext;import javax.servlet.http.HttpSessionEvent;import javax.servlet.http.HttpSessionListener;public class lister implements HttpSessionListener {
       @Override    public void sessionCreated(HttpSessionEvent se) {
           ServletContext ctx = se.getSession().getServletContext();        Integer lister = (Integer) ctx.getAttribute("lister");        if (lister==null){
               lister = new Integer(1);        }else{
               int i = lister.intValue();            lister =new Integer(i+1);        }        ctx.setAttribute("lister",lister);    }    //销毁    @Override    public void sessionDestroyed(HttpSessionEvent se) {
           ServletContext ctx = se.getSession().getServletContext();        Integer lister = (Integer) ctx.getAttribute("lister");        if (lister==null){
               lister = new Integer(0);        }else{
               int i = lister.intValue();            lister =new Integer(i-1);        }        ctx.setAttribute("lister",lister);    }}

xml

           
    
     com.listers.lister
        
       
           
    
     1
        
   

联系

package com.file;import javax.servlet.*;import java.io.IOException;public class selvlet_file  implements Filter {
       @Override    public void init(FilterConfig filterConfig) throws ServletException {
           System.out.println("初始化板书");    }    @Override    //chain链    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
           request.setCharacterEncoding("utf-8");        response.setCharacterEncoding("utf-8");        response.setContentType("text/html;charset=UTF-8");        System.out.println( "执行前    ");        chain.doFilter(request,response);        System.out.println( "执行过后");    }//过滤销毁    @Override    public void destroy() {
           System.out.println("销毁");    }}

   
       
            
     
      filer
             
     
      com.file.selvlet_file
         
        
            
     
      filer
             
     
      /servlet/*
         
        
            
     
      com.listers.lister
         
        
            
     
      1
         
    
   

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