Servlet Context

  • Defined in,

  javax.servlet.ServletContext (i/f)
  • Instance of ServletContext interface's implementation class is created by the container at the application deployment time.

  • Only one instance is created per web application.

  • NOTE : The ServletContext object is contained within the ServletConfig object, which the WC provides to the servlet once the servlet is initialized.

  • Usages

    • Server side logging.

        //Interface ServletContext
        public void log(String mesg)
    • To create context scoped (Application scoped) attributes.

        public void setAttribute(String name,Object val)

      NOTE : Access them always in thread safe manner. as they are mutable as it is a server side object.

  • To access global scoped (application scoped) attributes use,

     //Interface ServletContext
      Object getAttribute(String name)
  • To add context scoped attributes

      void setAttribute(String name, Object object)
  • web.xml tags to create context parameters, no annotations available

<context-param>
  <param-name>name</param-name>
  <param-value>value</param-value>
</context-param>
  • To access these parameters in a Servlet once the Servlet instance has initialized i.e init() method has been called.

  1. Get ServletContext

    • API of GenericServlet

  public ServletContext getServletContext() //method inherited from GenericServlet
  1. ServletContext API String getInitparameter(String paramName) : returns the parameter value. eg : ctx param name : user_name value : abc In the Servlet : getServletContext().getInitparameter("user_name") ---abc

5.4 Creating request dispatcher H.W

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