ServletContext example to get the initialization parameter from web.xml file

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class First
 */
@WebServlet("/First")
public class First extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

response.setContentType("text/html");
PrintWriter pw = response.getWriter();
ServletContext context=getServletContext();
String drivername = context.getInitParameter("dname");
pw.println("Driver Name is" +drivername);
pw.close();
}

}

web.xml

<web-app>  

  

<servlet>  

<servlet-name>First</servlet-name>  

<servlet-class>First</servlet-class>  

</servlet>  

  

<context-param>  

<param-name>dname</param-name>  

<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>  

</context-param>  

  

<servlet-mapping>  

<servlet-name>First</servlet-name>  

<url-pattern>/context</url-pattern>  

</servlet-mapping>  

  

</web-app>  

Output:-

ServletConfig example to get initialization parameter from web.xml

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class First
 */
@WebServlet("/First")
public class First extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
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>First</servlet-name>  

<servlet-class>First</servlet-class>  

  

<init-param>  

<param-name>driver</param-name>  

<param-value>sun.jdbc.odbc.JdbcOdbcDriver</param-value>  

</init-param>  

  

</servlet>  

  

<servlet-mapping>  

<servlet-name>First</servlet-name>  

<url-pattern>/servlet1</url-pattern>  

</servlet-mapping>  

  

</web-app>  

Output:-

Create a servlet example using (Implementing) Servlet interface

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class First
 */
@WebServlet("/First")
//public class First extends HttpServlet {
// private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#service(HttpServletRequest request, HttpServletResponse response)
*/
// protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
// }

//}




public class First implements Servlet{

ServletConfig con = null;

public void init(ServletConfig con){
this.con = con;
System.out.println("I am in init");
}

public void service(ServletRequest req,ServletResponse res) throws IOException,ServletException{
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.print("<html><body>");
out.print("<b>I am in Service</b>");
out.print("</html></body>");
}

public void destroy(){
System.out.println("I am in Destroy");
}
public ServletConfig getServletConfig(){return con;}
public String getServletInfo(){return "copyright 2007-1010";}
}

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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>Abc</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Output:-

First Java Servlet Program

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Hello
 */
@WebServlet("/Hello")
public class Hello extends HttpServlet {
private static final long serialVersionUID = 1L;

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub

response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.print("<html><body>");
out.print("<b>I am in Service</b>");
out.print("</html></body>");

}

}

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" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>SecondServlet</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

Output:-