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Servlet Init parameters and ServletConfig interface

Init parameters:

Init parameters refers to the initialization parameters of a servlet or filter. attribute is used to define a init parameter. attribute has two main sub attributes and . The contains the name of the parameter and contains the value of the parameter.

ServletConfig interface:

ServletConfig interface is used to access the init parameters.

Methods of ServletConfig interface:

1. getInitParameter(String name): Returns the value of the specified parameter if parameter exist otherwise return null.

Syntax: public String getInitParameter(String name)

2. getInitParameterNames(): Returns the names of init parameters as Enumeration if servlet has init parameters otherwise returns an empty Enumeration.

Syntax: public Enumeration getInitParameterNames()

3. getServletContext():Returns an instance of ServletContext.

Syntax: public ServletContext getServletContext()

4. getServletName():Returns the name of the servlet.

Syntax: public String getServletName()

Example:

InitParamExample.java

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * This class is used to show the use of init parameters.
 * @author javatutorialpoint
 */
public class InitParamExample extends HttpServlet {
 private static final long serialVersionUID = 1L;
 
        //no-argument constructor
        public InitParamExample() {
 
        }
 
      protected void doGet(HttpServletRequest request, 
  HttpServletResponse response)
           throws ServletException, IOException {
 response.setContentType("text/html"); 
     PrintWriter out = response.getWriter();
     //get ServletConfig object.
     ServletConfig config=getServletConfig(); 
     //get init parameter from ServletConfig object.
     String appUser = config.getInitParameter("appUser");
 
     out.print("
Application User: "
 + appUser + "

"); out.close(); } }

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">
 
<servlet>
    <servlet-name>InitParamExample</servlet-name>
    <servlet-class>
     com.javawithease.business.InitParamExample
    </servlet-class>
    <init-param>
     <param-name>appUser</param-name>
     <param-value>jai</param-value>
    </init-param>
  </servlet>
 
  <servlet-mapping>
    <servlet-name>InitParamExample</servlet-name>
    <url-pattern>/InitParamExample</url-pattern>
  </servlet-mapping>
 
</web-app>