<filter>
        <filter-name>SessionValidFilter</filter-name>
        <filter-class>web.filter.SessionValidFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>SessionValidFilter</filter-name>
        <url-pattern>/jsp/*</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>SessionValidFilter</filter-name>
        <url-pattern>*.do</url-pattern>
    </filter-mapping>
    <filter-mapping>
        <filter-name>SessionValidFilter</filter-name>
        <url-pattern>/servlet/*</url-pattern>
    </filter-mapping>

------解决方案--------------------
写个类，继承Filter。

然后在web.xml里面添加拦截

XML code

    <filter>
        <filter-name>filter名</filter-name>
        <filter-class>你的filter类路径</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>filter名</filter-name>
        <url-pattern>你要拦截的路径，如：/*</url-pattern>
    </filter-mapping>