Servlet过滤器和监听器配置范例

1，Servlet过滤器

<filter>
    <filter-name>charset</filter-name>
    <filter-class>org.guangsoft.filter.CharsetFilter</filter-class>
    <init-param>
        <param-name>encoding</param-name>
        <param-value>utf-8</param-value>
    </init-param>
</filter>

<filter-mapping>
        <filter-name>encoding</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>

Filter:
    package org.guangsoft.filter;

public class CharsetFilter implements Filter 
{
    private String encoding;
    public void init(FilterConfig filterconfig) throws ServletException 
    {
        this.encoding = filterconfig.getInitParameter("endcoding");
    }
    public void doFilter(ServletRequest req, ServletResponse resp,
            FilterChain chain) throws IOException, ServletException 
    {
        req.setCharacterEncoding(encoding);
        chain.doFilter(req, resp);
    }
    public void destroy() 
    {
    }
}
        

2,Servlet监听器

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);
    }
}