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JavaInterviewPoint

Java Development Tutorials

Get Configuration information – ServletConfig

June 5, 2015 by javainterviewpoint Leave a Comment

Each Servlet application allows you to configure and retrieve parameters via web.xml . You can specify initial parameter name/value pairs using <init-param> tag. In this example we will learn how to retrieve configuration information from the web.xml file.

To retrieve initial parameters, you need the ServletConfig object passed by the servlet container to the servlet. After you get the ServletConfig object, you can use either  getInitParameterNames and strong>getInitParameter methods.

  • The getInitParameterNames does not take an argument and returns an Enumeration containing all the parameter names in the ServletConfig object.
  • The getInitParameter takes a String containing the parameter name and returns a String containing the value of the parameter.

Since the servlet container passes a ServletConfig object to the init method, we will be writing our logic in the init() method itself. Here we will be configuring two initial parameters, the first parameter is  “admin” whose value will be “JavaInterviewPoint” and the second parameter is “admin_contact” and the value for the parameter is “123456789”. We will be implementing Servlet Interface to achieve this.

ServletConfigExample.java

Lets see the below Servlet Example which implements the Servlet Interface

package com.javainterviewpoint;

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

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class ServletConfigExample implements Servlet 
{
    public void init(ServletConfig config) throws ServletException 
    {
        Enumeration parameters = config.getInitParameterNames();
        while (parameters.hasMoreElements()) 
        {
            String parameter = (String) parameters.nextElement();
            System.out.println("Parameter name : " + parameter);
            System.out.println("Parameter value : " +
                    config.getInitParameter(parameter));
        }
    }
    public void destroy() 
    { }
    public void service(ServletRequest request, ServletResponse response)
        throws ServletException, IOException 
    { }
    public String getServletInfo() 
    { 
        return null;
    }
    public ServletConfig getServletConfig() 
    {
        return null;
    } 
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns="http://java.sun.com/xml/ns/javaee"	xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee	
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
	id="WebApp_ID" version="2.5">
     <display-name>ServletsInterfaceExample</display-name>
     <servlet>
         <servlet-name>ServletConfigExample</servlet-name>
         <servlet-class>com.javainterviewpoint.ServletConfigExample</servlet-class>
         <init-param>
              <param-name>admin</param-name>
              <param-value>JavaInterviewPoint</param-value>
         </init-param>
         <init-param>
               <param-name>admin_contact</param-name>
               <param-value>123456789</param-value>
         </init-param>
     </servlet>
     <servlet-mapping>
         <servlet-name>ServletConfigExample</servlet-name>
         <url-pattern>/ServletConfigExample</url-pattern>
     </servlet-mapping>
</web-app>

Output

To run our ServletConfigExample application hit on the below url

http://localhost:8080/ServletTutorial/ServletConfigExample

We will get the below output displayed in the browser

Parameter name : admin
Parameter value : JavaInterviewPoint
Parameter name : admin_contact
Parameter value : 123456789

Other interesting articles which you may like …

  • Difference between ServletConfig and ServletContext
  • How to change Tomcat default port from 8080 to Some Other?
  • Life Cycle of a Servlet
  • JSP Custom tags
  • Access body of Custom Tag in JSP
  • Attributes In Jsp Custom Tag
  • Running Your First Servlet Application
  • GenericServlet class
  • HttpServlet class
  • Difference Between GenericServlet and HttpServlet
  • welcome-file-list in web.xml of Servlets
  • ServletContext Interface in Servlets
  • Obtaining HTTP Request Headers from HttpServletRequest
  • ServletRequest Interface – Servlets
  • ServletResponse Interface – Servlets
  • Get Query String from Servlet Request

Filed Under: J2EE, Java, Servlets Tagged With: config, Configuration information, init-param, ServletConfig

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