java Filter过滤器

web.xml的配置

<init-para>里存放：过滤器初始化时要调用的值

<diapatcher>里存放：请求方式

<url-pattern>过滤条件
 sessionKey = filterConfig.getInitParameter("checkSessionKey"); 

<filter>
    <display-name>UserFilter</display-name>
    <filter-name>UserFilter</filter-name>
    <filter-class>com.cn.servlet.UserFilter</filter-class>
    <init-param>
    	<param-name>checkSessionKey</param-name>
    	<param-value>ss</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>UserFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
  </filter-mapping>