ServletConfig interface:

For each servlet, an instance of this interface is created by the container. With the help of this instance, information can be fetched from the configuration file (web.xml).

Advantage:

You don't need need to do changes in the servlet if any modifications are required. The configuration file can be updated and the changes will be reflected in the particular servlet. e.g. Database information can be kept in the configuration file, and if there is a migration to a new database, then you need to do the changes only in the web.xml file and it will be automatically reflected in the required servlet.

Get ServletConfig Object:

getServletConfig() This method of the interface is used to obtain the instance of ServletConfig.

To the value of the particular parameter we make use of the following methods:

1) public String getInitParameter(String name):Fetch the value for the given name.
2) public Enumeration getInitParameterNames():Fetch an enumeration of all the parameter names.

Example:

web.xml - In this file we specify the parameters.

  <servlet>  
    <servlet-name>Demo</servlet-name>  
    <servlet-class>Demp</servlet-class>  

    <init-param>  
    <param-name>name</param-name>  
    <param-value>Roth</param-value>  
    </init-param>  
   <init-param>  
    <param-name>password</param-name>  
    <param-value>Roth</param-value>  
    </init-param>  

    </servlet>  

    <servlet-mapping>  
    <servlet-name>Demo</servlet-name>  
    <url-pattern>/demo</url-pattern>  
    </servlet-mapping>  

    </web-app>  

Demo.java - Servlet used to fetch init parameters

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

public class Demo extends HttpServlet {  
public void doGet(HttpServletRequest request, HttpServletResponse response)  
    throws ServletException, IOException {  

    response.setContentType("text/html");  
    PrintWriter out = response.getWriter();  

    ServletConfig config=getServletConfig();  // getting the interface object
    String name=config.getInitParameter("name"); //fetching the name from the configuration file i.e. Roth
    String password=config.getInitParameter("password");//fetching the password from the configuration file i.e Roth
    out.print("Name is: "+name);    // This will print Roth in the output
    out.close();  
    }  

}