Why do we use web xml

Question

What is the use of web xml and why do we use    lt filter gt           lt filter-name gt wicket mysticpaste lt  filter-name gt           lt filter-class gt org apache wicket protocol http WicketFilter lt  filter-class gt           lt init-param gt               lt param-name gt applicationClassName lt  param-name gt               lt param-value gt com mysticcoders WicketApplication lt  param-value gt           lt  init-param gt       lt  filter gt     lt filter-mapping gt     lt filter-name gt wicket mysticpaste lt  filter-name gt       lt url-pattern gt    lt  url-pattern gt    lt  filter-mapping gt    What does this filer and filermapping do

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It s the default configuration for a Java web application  it s required   WicketFilter   is applied to every HTTP request that s sent to this web app

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The web xml file is the deployment descriptor for a Servlet-based Java web application  which most Java web apps are   Among other things  it declares which Servlets exist and which URLs they handle    The part you cite defines a Servlet Filter  Servlet filters can do all kinds of preprocessing on requests  Your specific example is a filter had the Wicket framework uses as its entry point for all requests because filters are in some way more powerful than Servlets

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Servlet to be accessible from a browser  then must tell the servlet container what servlets to deploy  and what URL s to map the servlets to  This is done in the web xml file of your Java web application   use web xml in servlet    lt servlet gt       lt description gt  lt  description gt       lt display-name gt servlet class name lt  display-name gt       lt servlet-name gt servlet class name lt  servlet-name gt       lt servlet-class gt servlet package name servlet class name lt  servlet-class gt   lt  servlet gt   lt servlet-mapping gt       lt servlet-name gt servlet class name lt  servlet-name gt       lt url-pattern gt  servlet class name lt  url-pattern gt   lt  servlet-mapping gt    manly use web xml for servlet mapping

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Web xml is called as deployment descriptor file  and its is is an XML file that contains information on the configuration of the web application  including the configuration of servlets

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Generally speaking  this is the configuration file of web applications in java  It instructs the servlet container  tomcat for ex   which classes to load  what parameters to set in the context  and how to intercept requests coming from browsers   There you specify    what servlets  and filters  you want to use and what URLs you want to map them to listeners - classes that are notified when some events happen  context starts  session created  etc  configuration parameters  context-params  error pages  welcome files security constraints    In servlet 3 0 many of the web xml parts are optional  These configurations can be done via annotations   WebServlet   WebListener

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It says all the requests to go through WicketFilter    Also  if you use   wicket WicketApplication for application level settings  Like URL patterns and things that are true at app level    This is what you need really  http   wicket apache org learn examples helloworld html

[java] Why do we use web.xml?

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