Filter过滤器

过滤器是什么？
是一个对象，用于对任务的过滤，这个任务可能是对一个资源的请求，也有可能是一个资源的响应。以下是filter的interface的英文源码介绍：

A filter is an object that performs filtering tasks on either the request to a resource (a servlet or static content), or on the response from a resource, or both.

过滤器用来干嘛？
1.认证过滤
2.日志和审查过滤
3.图形转换过滤
4.数据压缩过滤
5.令牌过滤
6.触发资源访问事件过滤
7.xsl转换滤过
8.多媒体类型过滤
以下是filter的interface的英文源码介绍：

** Examples that have been identified for this design are<br>    ** 1) Authentication Filters <br>    ** 2) Logging and Auditing Filters <br>    ** 3) Image conversion Filters <br>        ** 4) Data compression Filters <br>    ** 5) Encryption Filters <br>    ** 6) Tokenizing Filters <br>    ** 7) Filters that trigger resource access events <br>    ** 8) XSL/T filters <br>    ** 9) Mime-type chain Filter <br>