filter 的使用执行过程 和 listener 监听器的使用

 <filter>
    <description>使用tomcat自带过滤器</description>
    <filter-name>LoginFilter</filter-name>
    <filter-class>org.apache.catalina.filters.SetCharacterEncodingFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>LoginFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>