ServletConfig Interface

A ServletConfig is generated by the Web Container for each and every servlet. This Object can be made use to get Configuration data from web.xml file.

If the configuration information is changed from the web.xml file, we don’t require to change the servlet. So, it is effortless to manage the web application if any defined content is amended from time to time.

Benefits of ServletConfig

The most important advantage of servletconfig is that there is no need to edit the file if information is changed from the web.xml file.

Ways of ServletConfig interface are:

• public String getInitParameter(String name): Come back to the parameter value for the defined parameter name.
• public Enumeration getInitParameterNames(): Come back an enumeration of all the starting parameters names
• public String getServletName(): Come back the name of the servlet
• public ServletContext getServletContext(): Come back of an object of the servlet Context

How to get the object ServletConfig

1. getServletConfig() method of Servlet interface comes back the object of ServletConfig.

Syntax of getServletConfig() method

public ServletConfig getServletConfig();  

Example of getServletConfig() method

ServletConfig config=getServletConfig();  
//Now we can call the methods of ServletConfig interface  

Syntax to give the initialization Parameter for a Servlet:

The init param sub-element of the servlet is used to define the initialization parameter of the servlet.

<web-app>  
  <servlet>  
    ......    
    <init-param>  
      <param-name>parametername</param-name>  
      <param-value>parametervalue</param-value>  
    </init-param>  
    ......  
  </servlet>  
</web-app> 

Example of ServletConfig to get initialization Parameter

We are getting the one initialization parameter from the web.xml file and printing this information in the servlet. In the below given example let’s see how.

DemoServlet.java

import java.io.*;  
import javax.servlet.*;  
import javax.servlet.http.*;  
public class DemoServlet extends HttpServlet {  
public void doGet(HttpServletRequest request, HttpServletResponse response)  
    throws ServletException, IOException {  
    response.setContentType("text/html");  
    PrintWriter out = response.getWriter();       
    ServletConfig config=getServletConfig();  
    String driver=config.getInitParameter("driver");  
    out.print("Driver is: "+driver);         
    out.close();  
    }  
}  

Web.xml

<web-app>  
<servlet>  
<servlet-name>DemoServlet</servlet-name>  
<servlet-class>DemoServlet</servlet-class>  
<init-param>  
<param-name>driver</param-name>  
<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>  
</init-param>    
</servlet>  
<servlet-mapping>  
<servlet-name>DemoServlet</servlet-name>  
<url-pattern>/servlet1</url-pattern>  
</servlet-mapping>   
</web-app>  

Example of servletconfig to get all the initialization parameters:

We are Getting all the initialization parameters from the web.xml file and printing this information in Servlet, In the below given example.

DemoServlet.java

import java.io.IOException;  
import java.io.PrintWriter;  
import java.util.Enumeration;  

import javax.servlet.ServletConfig;  
import javax.servlet.ServletException;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  

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

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

    ServletConfig config=getServletConfig();  
    Enumeration<String> e=config.getInitParameterNames();        

    String str="";  
    while(e.hasMoreElements()){  
    str=e.nextElement();  
    out.print("<br>Name: "+str);  
    out.print(" value: "+config.getInitParameter(str));  
    }           
    out.close();  
}  

}  

Web.xml

<web-app>  
<servlet>  
<servlet-name>DemoServlet</servlet-name>  
<servlet-class>DemoServlet</servlet-class>  

<init-param>  
<param-name>username</param-name>  
<param-value>system</param-value>  
</init-param>   

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

</servlet>  
  
<servlet-mapping>  
<servlet-name>DemoServlet</servlet-name>  
<url-pattern>/servlet1</url-pattern>  
</servlet-mapping>  

</web-app>