How to make Filter getting called only once for every User

[Ravi Kiran Va]

Hi , i have a filter configured as shown below inside my web.xml file ,

<filter> 
		<filter-name>UTFilter</filter-name> 
		<filter-class>com.common.util.UTFilter</filter-class> 
	</filter> 
	
	<filter-mapping> 
		<filter-name>UTF8Filter</filter-name> 
		<url-pattern>/*</url-pattern> 
	</filter-mapping> 

I see that this Filter is being called for every request and response .

Actually , my requirement is that , the Filter servlet should be called only once for every user log in .

Please help as how can i do this ??

Thanks .

[Paul Sturrock]

Filters are called for every request made to the filtered resource - that is their purpose, there is no way to declaretively specify a filter for the first request by a client and ignore all others. The logic you write in your filter can do what it likes though.

[Ravi Kiran Va]

Thank you very much .

[Radovan Vukovic]

Ravi Kiran Va wrote:
Actually , my requirement is that , the Filter servlet should be called only once for every user log in .

Do this means that you have some kind login transaction (servlet or whatever )?
If it’s so I think that you can map this for some specific servlet

<filter-mapping>   
          <filter-name>UTF8Filter</filter-name>   
          <url-pattern>/login</url-pattern>   
</filter-mapping> 

Before couple of years I was working with acegi security and should be that acegi filter chain proxy is defined on similar way

It’s just idea could be that am wrong

[Paul Sturrock]

Why use a filter at all when the action maps to a distinct Servlet? What does this give you that you can't do directly in the Servlet?

[Ravi Kiran Va]

Why use a filter at all when the action maps to a distinct Servlet? What does this give you that you can't do directly in the Servlet?

In my case it is something related to setting the character set to UTF-8 .

As per your previous answer

"The logic you write in your filter can do what it likes though."

You mean to use in this way inside doFilter()

if(somecondition)
{
}
else
{
chaain.doFilter(req,res);
}

}

Please correct me if i am wrong . Thanks in advance .

[Paul Sturrock]

In my case it is something related to setting the character set to UTF-8 .

Is that safe? Why do that rather than setting the content-type header? And why set the character set just for a single request - surely if you are doing it at all you need it for all requests?

[Todd Buell]

Could you just set a session attribute as an indicator that the filter has been executed for this user's session. If it's not present, execute the filter code, set the value then continue on. If the session value is present this session must have already executed so short-circuit any processing and just continue.

example:

 
private static final String FLAG = "FLAG";

public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) ...
{
    HttpSession session = ((HttpServletRequest)request).getSession();
    String flag = session.getAttribute(FLAG);
    if(flag != null) {
        // do processing
        session.setAttribute(FLAG, FLAG);
    }
    chain.doFilter(request, response);
}