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Introduction to ServletConfig interface

When the Web Container initializes a servlet, it creates a ServletConfig object for the servlet. ServletConfig object is used to pass information to a servlet during initialization by getting configuration information from web.xml(Deployment Descriptor).


Methods of ServletConfig

  • String getInitParameter(String name): returns a String value initialized parameter, or NULL if the parameter does not exist.
  • Enumeration getInitParameterNames(): returns the names of the servlet's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the servlet has no initialization parameters.
  • ServletContext getServletContext(): returns a reference to the ServletContext
  • String getServletName(): returns the name of the servlet instance

How to Initialize a Servlet inside web.xml

In the Deployment Descriptor(web.xml) file,

how to initialize a servlet using deployment descriptor

Or, Inside the Servlet class, using following code,


 ServletConfig sc = getServletConfig();
 out.println(sc.getInitParameter("email"));

Example demonstrating usage of ServletConfig

web.xml

<web-app...>
   <servlet>
      <servlet-name>check</servlet-name>
      <servlet-class>MyServlet</servlet-class>
      <init-param>
            <param-name>email</param-name>
            <param-value>we@studytonight.com</param-value>
      </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>check</servlet-name>
        <url-pattern>/check</url-pattern>
    </servlet-mapping>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
     </welcome-file-list>   
</web-app>

MyServlet class :

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class MyServlet extends HttpServlet {

  protected void doGet(HttpServletRequest request, HttpServletResponse response)
         throws ServletException, IOException {
       
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        ServletConfig sc = getServletConfig();
        out.println(sc.getInitParameter("email")); 
    }
}