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Filters

 
sitaram irrinki
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while i am working with FILTERS in java,

1) Is it compulsary to have a servlet when working with filter and

2) if i want to call a specific servlet using filters then how should we proceed.

please explain me with an example if possible along with deployment descriptor
 
Scheepers de Bruin
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No it's not mandatory to have a servlet in order to use a filter.

Say we have a filter:
<filter>
<filter-name>security</filter-name>
<filter-class>za.co.security.SecurityFilter</filter-class>
</filter>

<filter-mapping>
<filter-name>security</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>

This will filter ALL requests received, irrespective of the resource requested. Images, pages, stylesheets, the works.

I'm not entirely sure what you ment by calling a servlet using a filter, but I suspect you either want to redirect to the servlet url, or request a servlet resource while processing a user request.

1) Redirecting:
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException
{
response.sendRedirect("/myservletUrl.jsp");
return;
}

2) Requesting a servlet:
{
java.net.URL url = new java.net.URL("htpp://myserver/myServlet.go");
InputStream myStream = url.openStream();
//Code to read servlets' response from the myStream InputStream
}
 
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