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Categories: Servlets. No Comments on Retrieving Parameters in Servlets
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It is common in web applications to pass data or parameters from one to another page. To retrieve the values of various elements in a HTML form or from another page, we can use the following methods which are available in HttpServletRequest object:

  • String getParameter(String  name)
  • Enumeration getParameterNames()
  • String[] getParamterValues(String  name)

 

Following example demonstrates retrieving data from a login page to a servlet:

 

login.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login</title>
</head>
<body>
	<form action="auth.html" method="get">
		Username: <input type="text" name="txtuser" /><br />
		Password: <input type="password" name="txtpass" /><br />
		<input type="submit" value="Submit" />
		<input type="reset" value="Clear" />
	</form>
</body>
</html>

 

web.xml


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<?xml version="1.0" encoding="UTF-8"?>
<web-app>
  <servlet>
    <servlet-name>Authenticate</servlet-name>
    <servlet-class>Authenticate</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>Authenticate</servlet-name>
    <url-pattern>/auth.html</url-pattern>
  </servlet-mapping>
</web-app>

 

Authenticate.java

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Authenticate
 */
public class Authenticate extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public Authenticate() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse 		response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) 	throws ServletException, IOException {
		String username = request.getParameter("txtuser");
		String password = request.getParameter("txtpass");
		if(username.equals("vishnu") && password.equals("college"))
		{
			response.getWriter().print("Valid user!");
		}
		else
		{
			response.getWriter().print("Bad username or password");
		}
	}
}

 

In the above example we are retrieving the data from login page using the getParameter() method.

 

Video: Retrieving Parameters

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Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.

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