public void init(FilterConfig config) throws ServletException {
        this.filterConfig = config;
        this.encoding = filterConfig.getInitParameter("encoding");  //从web.xml文件中读取encoding的值
        String value = filterConfig.getInitParameter("ignore");     //从web.xml文件中读取ignore的值
        //以下三种情况均为忽略大小写
        if (value == null)
            this.ignore = true;
        else if (value.equalsIgnoreCase("true"))
            this.ignore = true;
        else if (value.equalsIgnoreCase("yes"))
            this.ignore = true;
        else
            this.ignore = false;
    }