On Wed, 20 Feb 2002, GuruPrasad wrote:
> Date: Wed, 20 Feb 2002 10:59:55 -0800 (PST)
> From: GuruPrasad <[EMAIL PROTECTED]>
> Reply-To: Tomcat Developers List <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
> Subject: Difference between Valve and javax.servlet.Filter?
>
> What are the difference between Valve and Filter?
>
Valves and Filters implement the same design pattern ("Chain of
Responsibility" from the GoF book), so they can be used for similar sorts
of things. However, there are a couple of key differences:
* Filters are part of the servlet spec, and therefore portable
to any Servlet 2.3 environment, while Valves are specific
to Tomcat 4.x.
* Filters have access to ServletRequest and ServletResponse objects,
and can optionally wrap them to provide modified functionality.
Valves have access to the internal Request and Response implementation
objects, which have a lot more functionality -- you can often
implement things by calling a property setter on the object directly
instead of by wrapping it.
The rule of thumb to use: if you can implement your required
functionality as a Filter or as a Valve, use a Filter to protect the
portability of your application.
> -
> Thanks,
> prasad
>
Craig
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