kaptcha验证码组件使用简介

Kaptcha是一个基于SimpleCaptcha的验证码开源项目。

官网地址:http://code.google.com/p/kaptcha/

 

kaptcha的使用比较方便,只需添加jar包依赖之后简单地配置就可以使用了。kaptcha所有配置都可以通过web.xml来完成,如果你的项目中使用了Spring MVC,那么则有另外的一种方式来实现。

 

一、简单的jsp-servlet项目

1.添加jar包依赖

如果你使用maven来统一管理jar包,则在工程的pom.xml中添加dependency

<!-- kaptcha -->
<dependency>
	<groupId>com.google.code.kaptcha</groupId>
	<artifactId>kaptcha</artifactId>
	<version>2.3.2</version>
</dependency>

如果是非maven管理的项目,则直接在官网下载kaptcha的jar包,然后添加到项目lib库中,下载地址:http://code.google.com/p/kaptcha/downloads/list

 

 

2.配置web.xml

上面说了,kaptcha都是在web.xml中配置,我们必须在web.xml中配置kaptcha的servlet,具体如下:

<servlet>
	<servlet-name>Kaptcha</servlet-name>
	<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
	<servlet-name>Kaptcha</servlet-name>
	<url-pattern>/kaptcha.jpg</url-pattern>
</servlet-mapping>

其中servlet的url-pattern可以自定义。

 

kaptcha所有的参数都有默认的配置,如果我们不显示配置的话,会采取默认的配置。

如果要显示配置kaptcha,在配置kaptcha对应的Servlet时,在init-param增加响应的参数配置即可。示例如下:

<servlet>
	<servlet-name>Kaptcha</servlet-name>
	<servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
	<init-param>
		<param-name>kaptcha.image.width</param-name>
		<param-value>200</param-value>
		<description>Width in pixels of the kaptcha image.</description>
	</init-param>
	<init-param>
		<param-name>kaptcha.image.height</param-name>
		<param-value>50</param-value>
		<description>Height in pixels of the kaptcha image.</description>
	</init-param>
	<init-param>
		<param-name>kaptcha.textproducer.char.length</param-name>
		<param-value>4</param-value>
		<description>The number of characters to display.</description>
	</init-param>
	<init-param>
		<param-name>kaptcha.noise.impl</param-name>
		<param-value>com.google.code.kaptcha.impl.NoNoise</param-value>
		<description>The noise producer.</description>
	</init-param>
</servlet>

具体的配置参数参见:http://code.google.com/p/kaptcha/wiki/ConfigParameters

 

3.页面调用

<form action="submit.action">
	<input type="text" name="kaptcha" value="" /><img src="kaptcha.jpg" />
</form>

 

4.在submit的action方法中进行验证码校验

//从session中取出servlet生成的验证码text值
String kaptchaExpected = (String)request.getSession().getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
//获取用户页面输入的验证码
String kaptchaReceived = request.getParameter("kaptcha");
//校验验证码是否正确
if (kaptchaReceived == null || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)){
	setError("kaptcha", "Invalid validation code.");
}

注:确保JDK设置了 -Djava.awt.headless=true

 

5.实现页面验证码刷新

<img src="kaptcha.jpg" width="200" id="kaptchaImage" title="看不清,点击换一张" />
<script type="text/javascript">
	$(function() {
		$('#kaptchaImage').click(function() {$(this).attr('src','kaptcha.jpg?' + Math.floor(Math.random() * 100));});
	});
</script>
<br /><small>看不清,点击换一张</small>

注:为了避免浏览器的缓存,可以在验证码请求url后添加随机数

 

二、Spring mvc项目中使用kaptcha

1.添加captchaProducer bean定义

<!-- 配置kaptcha验证码 -->
<bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
	<property name="config">
		<bean class="com.google.code.kaptcha.util.Config">
			<constructor-arg type="java.util.Properties">
				<props>
					<prop key="kaptcha.image.width">100</prop>
					<prop key="kaptcha.image.height">50</prop>
					<prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoise</prop>
					<prop key="kaptcha.textproducer.char.string">0123456789abcdefghijklmnopqrstuvwxyz</prop>
					<prop key="kaptcha.textproducer.char.length">4</prop>
				</props>
			</constructor-arg>
		</bean>
	</property>
</bean>

2.生成验证码的Controller

import java.awt.image.BufferedImage;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

import com.google.code.kaptcha.Constants;
import com.google.code.kaptcha.Producer;

/**
 * ClassName: CaptchaImageCreateController <br/>
 * Function: 生成验证码Controller. <br/>
 * date: 2013-12-10 上午11:37:42 <br/>
 *
 * @author [email protected]
 */
@Controller
public class CaptchaImageCreateController {
	private Producer captchaProducer = null;

	@Autowired
	public void setCaptchaProducer(Producer captchaProducer){
		this.captchaProducer = captchaProducer;
	}

	@RequestMapping("/kaptcha.jpg")
	public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception{
		// Set to expire far in the past.
		response.setDateHeader("Expires", 0);
		// Set standard HTTP/1.1 no-cache headers.
		response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
		// Set IE extended HTTP/1.1 no-cache headers (use addHeader).
		response.addHeader("Cache-Control", "post-check=0, pre-check=0");
		// Set standard HTTP/1.0 no-cache header.
		response.setHeader("Pragma", "no-cache");

		// return a jpeg
		response.setContentType("image/jpeg");

		// create the text for the image
		String capText = captchaProducer.createText();

		// store the text in the session
		request.getSession().setAttribute(Constants.KAPTCHA_SESSION_KEY, capText);

		// create the image with the text
		BufferedImage bi = captchaProducer.createImage(capText);

		ServletOutputStream out = response.getOutputStream();

		// write the data out
		ImageIO.write(bi, "jpg", out);
		try {
			out.flush();
		} finally {
			out.close();
		}
		return null;
	}
}

 

3.校验用户输入的Controller

/**
 * ClassName: LoginController <br/>
 * Function: 登录Controller. <br/>
 * date: 2013-12-10 上午11:41:43 <br/>
 *
 * @author [email protected]
 */
@Controller
@RequestMapping("/login")
public class LoginController {

	/**
	 * loginCheck:ajax异步校验登录请求. <br/>
	 *
	 * @author [email protected]
	 * @param request
	 * @param username 用户名
	 * @param password 密码
	 * @param kaptchaReceived 验证码
	 * @return 校验结果
	 * @since 2013-12-10
	 */
	@RequestMapping(value = "check", method = RequestMethod.POST)
	@ResponseBody
	public String loginCheck(HttpServletRequest request,
			@RequestParam(value = "username", required = true) String username,
			@RequestParam(value = "password", required = true) String password,
			@RequestParam(value = "kaptcha", required = true) String kaptchaReceived){
		//用户输入的验证码的值
		String kaptchaExpected = (String) request.getSession().getAttribute(
				com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
		//校验验证码是否正确
		if (kaptchaReceived == null || !kaptchaReceived.equals(kaptchaExpected)) {
			return "kaptcha_error";//返回验证码错误
		}
		//校验用户名密码
		// ……
		// ……
		return "success"; //校验通过返回成功
	}
}

 

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