Servlet that generates Captcha image.
Let's see how our Captcha application works.
Working of the application
- captcha.jsp: This page contains the captcha image and one text field.
- User reads the image text and then enters in the "Code" text field. After entering the value in the text field, user clicks on the "Verify" command button.
- Then our Struts 2 action validates the user input and the session Captcha value. If user enters the correct image code in the text filed, then action forward to the "success.jsp" page. Otherwise, it gives an error and go to again the "captcha.jsp".
Index page
In the index.html we have added a link to captcha.jsp. User can click on this link to go to the captcha form.
| <html> <head> <title>Capcha Validation</title> <style> a:link{ color:red; text-decoration:underline; } a:visited{ color:red; text-decoration:underline; } a:hover{ color:green; text-decoration:none; } a:active{ color:red; text-decoration:underline; } </style> </head> <body> <table> <tr><td><a href="captcha.jsp">Captcha Application</a></td></tr> </table> </body> </html> |
2. Captcha Page
The GUI of the application consists of Captcha page (captcha.jsp).
The captcha.jsp is used to display the valid code and a text box.
<%@ taglib prefix="s" uri="/struts-tags" %>The GUI of the application consists of Captcha page (captcha.jsp).
The captcha.jsp is used to display the valid code and a text box.
<html>
<head>
<title>Capcha Validation</title>
<style>
.errorMessage {
color: red;
font-size: 0.8em;
}
.label {
color:#000000;
}
</style>
</head>
<body>
<table>
<tr>
<td>
<h1>Captcha Validation</h1>
<s:form action="doCaptcha" method="POST">
<s:actionerror />
<img src="Captcha.jpg" border="0">
<s:textfield label="Code" name="j_captcha_response" size="20" maxlength="10"/>
<s:submit value="Verify" align="center" />
</s:form>
</td>
</tr>
</table>
</body>
</html>
The code :
<s:actionerror />
<s:actionerror />
displays action errors and field validation errors.
The code <s:form action="doLogin" method="POST"> generates the html form for the application.
The code :
The code :
<img src="Captcha.jpg" border="0">
<s:textfield label="Code" name="j_captcha_response" size="20" maxlength="10"/>
<s:textfield label="Code" name="j_captcha_response" size="20" maxlength="10"/>
The submit button is generated through <s:submit value="Verify" align="center" /> code.
3. Servlet Class
Develop a Servlet class "RoseIndiaCaptcha.java" to create a Captcha image. Here is the code ofRoseIndiaCaptcha.java Servlet class:
Develop a Servlet class "RoseIndiaCaptcha.java" to create a Captcha image. Here is the code ofRoseIndiaCaptcha.java Servlet class:
package com.roseindiaCaptcha.servlet;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import javax.servlet.http.*;
import javax.servlet.*;
import java.io.*;
import java.awt.*;
import java.util.*;
import java.awt.font.TextAttribute;
public class RoseIndiaCaptcha extends HttpServlet {
private int height=0;
private int width=0;
public static final String CAPTCHA_KEY = "captcha_key_name";
public void init(ServletConfig config) throws ServletException {
super.init(config);
height=Integer.parseInt(getServletConfig().getInitParameter("height"));
width=Integer.parseInt(getServletConfig().getInitParameter("width"));
}
protected void doGet(HttpServletRequest req, HttpServletResponse response)
throws IOException, ServletException {
//Expire response
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
response.setHeader("Pragma", "no-cache");
response.setDateHeader("Max-Age", 0);
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics2D graphics2D = image.createGraphics();
Hashtable map = new Hashtable();
Random r = new Random();
String token = Long.toString(Math.abs(r.nextLong()), 36);
String ch = token.substring(0,6);
Color c = new Color(0.6662f, 0.4569f, 0.3232f);
GradientPaint gp = new GradientPaint(30, 30, c, 15, 25, Color.white, true);
graphics2D.setPaint(gp);
Font font=new Font("Verdana", Font.CENTER_BASELINE , 26);
graphics2D.setFont(font);
graphics2D.drawString(ch,2,20);
graphics2D.dispose();
HttpSession session = req.getSession(true);
session.setAttribute(CAPTCHA_KEY,ch);
OutputStream outputStream = response.getOutputStream();
ImageIO.write(image, "jpeg", outputStream);
outputStream.close();
}
}
4.Mapping for Servlet class in web.xml
<servlet>
<servlet-name>Captcha</servlet-name>
<display-name>Captcha</display-name>
<servlet-class>com.roseindiaCaptcha.servlet.RoseIndiaCaptcha</servlet-class>
<init-param>
<description>passing height</description>
<param-name>height</param-name>
<param-value>30</param-value>
</init-param>
<init-param>
<description>passing height</description>
<param-name>width</param-name>
<param-value>120</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Captcha</servlet-name>
<url-pattern>/Captcha.jpg</url-pattern>
</servlet-mapping>
<servlet-name>Captcha</servlet-name>
<display-name>Captcha</display-name>
<servlet-class>com.roseindiaCaptcha.servlet.RoseIndiaCaptcha</servlet-class>
<init-param>
<description>passing height</description>
<param-name>height</param-name>
<param-value>30</param-value>
</init-param>
<init-param>
<description>passing height</description>
<param-name>width</param-name>
<param-value>120</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Captcha</servlet-name>
<url-pattern>/Captcha.jpg</url-pattern>
</servlet-mapping>
5.Success page
After successful validation page transfer to the "success.page"
| <html> <head> <title>Capcha Validation</title> </head> <body> <table><tr><td><h1>You are Succesfully Validate</h1></td></tr></table> </body> </html> |
6.Developing Action Class
Now let's develop the action class to handle the Captcha validation request.
Now let's develop the action class to handle the Captcha validation request.
The code String c= (String)session.getAttribute(RoseIndiaCaptcha.CAPTCHA_KEY) is used to get the Captcha value stored in session and then validate it with the user input. Here is the code of the Action class.
package com.roseindiaCaptcha.action;
import com.opensymphony.xwork2.ActionSupport;
import java.util.Date;
import javax.servlet.http.*;
import javax.servlet.*;
import com.opensymphony.xwork2.ActionContext;
import com.roseindiaCaptcha.servlet.*;
public class CaptchaAction extends ActionSupport {
public String execute() throws Exception {
HttpServletRequest request = (HttpServletRequest)
ActionContext.getContext().get(org.apache.struts2.StrutsStatics.HTTP_REQUEST);
Boolean isResponseCorrect = Boolean.FALSE;
javax.servlet.http.HttpSession session = request.getSession();
String parm = request.getParameter("j_captcha_response");
String c= (String)session.getAttribute(RoseIndiaCaptcha.CAPTCHA_KEY) ;
if(!parm.equals(c) ){
addActionError("Invalid Code! Please try again!");
return ERROR;
}else{
return SUCCESS;
}
}
}
7.Configuring action mapping (in struts.xml) Now we will create action mapping in the struts.xml file. Here is the code to be added in the struts.xml:<action name="doCaptcha" class="com.roseindiaCaptcha.action.CaptchaAction"><result name="error">captcha.jsp</result><result>success.jsp</result></action>In the above mapping the action "doCaptcha" is used to validates the user using action class (CaptchaAction.java).
