Kaptcha is an open-source project that builds upon the SimpleCaptcha verification code system. It offers a more user-friendly approach, allowing developers to easily integrate it into their projects by simply adding the JAR dependency and making basic configurations. All Kaptcha settings can be managed through the `web.xml` file. If your project uses Spring MVC, there's an alternative configuration method available.
To start using Kaptcha in a simple JSP-Servlet project, follow these steps:
1. **Add JAR Dependencies**
If you're using Maven to manage dependencies, add the following to your `pom.xml` file:
```xml
com.google.code.kaptcha
kaptcha
2.3.2
```
For non-Maven projects, download the Kaptcha JAR from the official website and add it to your project's library folder.
2. **Configure web.xml**
You need to define the Kaptcha servlet in your `web.xml`. Here's a sample configuration:
```xml
Kaptcha
com.google.code.kaptcha.servlet.KaptchaServlet
kaptcha.image.width
200
Width in pixels of the Kaptcha image.
kaptcha.image.height
50
Height in pixels of the Kaptcha image.
kaptcha.textproducer.char.length
4
The number of characters to display.
kaptcha.noise.impl
com.google.code.kaptcha.impl.NoNoise
The noise producer.
Kaptcha
/kaptcha.jpg
```
The `url-pattern` can be customized based on your needs. If no custom parameters are set, default values will be used.
3. **Display the Image on the Page**
In your HTML form, include the Kaptcha image using the following code:
```html
```
4. **Verify the Code in the Submit Action**
In your Java backend (e.g., in a Struts or Spring MVC action), retrieve the generated Kaptcha text from the session and compare it with the user input:
```java
String kaptchaExpected = (String) request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
String kaptchaReceived = request.getParameter("kaptcha");
if (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)) {
// Handle invalid CAPTCHA
setError("kaptcha", "Invalid validation code.");
}
```
Make sure to set the `-Djava.awt.headless=true` flag in your JVM options, as Kaptcha requires a graphical environment for image generation.
By following these steps, you can effectively integrate Kaptcha into your web application, ensuring secure and easy-to-use CAPTCHA functionality.
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