Servlet过滤器和监听器配置范例

 1 <filter>
 2     <filter-name>charset</filter-name>
 3     <filter-class>org.guangsoft.filter.CharsetFilter</filter-class>
 4     <init-param>
 5         <param-name>encoding</param-name>
 6         <param-value>utf-8</param-value>
 7     </init-param>
 8 </filter>
 9 
10 <filter-mapping>
11         <filter-name>encoding</filter-name>
12     <url-pattern>/*</url-pattern>
13 </filter-mapping>
14 
15 Filter:
16     package org.guangsoft.filter;
17 
18 public class CharsetFilter implements Filter 
19 {
20     private String encoding;
21     public void init(FilterConfig filterconfig) throws ServletException 
22     {
23         this.encoding = filterconfig.getInitParameter("endcoding");
24     }
25     public void doFilter(ServletRequest req, ServletResponse resp,
26             FilterChain chain) throws IOException, ServletException 
27     {
28         req.setCharacterEncoding(encoding);
29         chain.doFilter(req, resp);
30     }
31     public void destroy() 
32     {
33     }
34 }
35         

Web.xml:
    <listener>
        <listener-class>org.guangsoft.listener.CountListener</listener-class>
</listener>
Listener:
public class CountListener implements HttpSessionListener 
{
    private ServletContext sc = null;
    public void sessionCreated(HttpSessionEvent se) 
　　{
        this.sc = se.getSession().getServletContext();
        Integer i = (Integer) this.sc.getAttribute("online");
        if (i == null)
            i = new Integer(0);
        i = new Integer((i.intValue()) + 1);
        this.sc.setAttribute("online", i);
    }
    public void sessionDestroyed(HttpSessionEvent httpsessionevent) 
　　{
        Integer i = (Integer) this.sc.getAttribute("online");
        if (i == null)
            i = new Integer(1);
        i = new Integer((i.intValue()) - 1);
        this.sc.setAttribute("online", i);
    }
}