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Why does GenericServlet implements ServletConfig?

Faisal Ahmad
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Joined: Aug 31, 2006
Posts: 355

I've beginner level of Servlet/JSP knowledge.

Is it right to say, a servlet that we write IS-A ServletConfig? Further, why a servlet has to implement ServletConfig interface? It gets an object of ServletConfig through its init method. Which means, a servlet HAS-A ServletConfig. In spite of this, why it implements ServletConfig interface?
bhanu chowdary
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Joined: Mar 09, 2010
Posts: 256
Faisal,

why a servlet has to implement ServletConfig interface?


Servlet Please go through the Servlet interface. I dont think there is any hard coded rule saying that a servlet has to implement ServletConfig. Moreover the servletConfig object is made by the container and passed to the init(servletConfig) in your servlet.
Faisal Ahmad
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Joined: Aug 31, 2006
Posts: 355

Servlet interface doesn't implement ServletConfig. But, why does GenericServlet? Already it HAS-A ServletConfig! In spite of this, what is the purpose of implementing a ServletConfig? I find it difficult to agree with this sentence: "A servlet IS-A ServletConfig". It's confusing.
Faisal Ahmad
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Joined: Aug 31, 2006
Posts: 355

Moderators!

I want to rename the title of this thread to "Why does GenericServlet implements ServletConfig?"

Could you please help? Thanks!
Milan Sutaria
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Joined: Jul 10, 2008
Posts: 122
Even I am preparing for SCWCD and am curious to know. If a servlet IS-A servletConfig why does the container has to pass a servletConfig to servlet:init(ServletConfig)?
(this is altogether a different question from the original)
Thanks for your thoughts


SCJP 6 83%
Working on SCWCD/OCPJWCD
Ulf Dittmer
Marshal

Joined: Mar 22, 2005
Posts: 42913
    
  68
You need to differentiate between Servlet and GenericServlet. Servlet (which is an interface) does not implement ServletConfig, whereas GenericServlet (an actual class) does. It's perfectly possible (although very uncommon) for a servlet to implement Servlet instead of extending GenericServlet or HttpServlet.

As a bit of a history lesson (for those who have not been using the Servlet API for a dozen years or so...), GenericServlet originally did not implement ServletConfig; that was something that got added later as a convenience. So the ServletConfig object passed in via the init method was the one you had to use.
Milan Sutaria
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Joined: Jul 10, 2008
Posts: 122
Thanks Ulf
 
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subject: Why does GenericServlet implements ServletConfig?