kaptcha验证码组件使用简介

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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

<dependency>
    <groupId>com.google.code.kaptchagroupId>
    <artifactId>kaptchaartifactId>
    <version>2.3.2version>
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>Kaptchaservlet-name>
    <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
servlet>
<servlet-mapping>
    <servlet-name>Kaptchaservlet-name>
    <url-pattern>/kaptcha.jpgurl-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>Kaptchaservlet-name>
    <servlet-class>com.google.code.kaptcha.servlet.KaptchaServletservlet-class>
    <init-param>
        <param-name>kaptcha.image.widthparam-name>
        <param-value>200param-value>
        <description>Width in pixels of the kaptcha image.description>
    init-param>
    <init-param>
        <param-name>kaptcha.image.heightparam-name>
        <param-value>50param-value>
        <description>Height in pixels of the kaptcha image.description>
    init-param>
    <init-param>
        <param-name>kaptcha.textproducer.char.lengthparam-name>
        <param-value>4param-value>
        <description>The number of characters to display.description>
    init-param>
    <init-param>
        <param-name>kaptcha.noise.implparam-name>
        <param-value>com.google.code.kaptcha.impl.NoNoiseparam-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

<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">100prop>
                    <prop key="kaptcha.image.height">50prop>
                    <prop key="kaptcha.noise.impl">com.google.code.kaptcha.impl.NoNoiseprop>
                    <prop key="kaptcha.textproducer.char.string">0123456789abcdefghijklmnopqrstuvwxyzprop>
                    <prop key="kaptcha.textproducer.char.length">4prop>
                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
 * Function: 生成验证码Controller.
 * date: 2013-12-10 上午11:37:42
 *
 * @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
 * Function: 登录Controller.
 * date: 2013-12-10 上午11:41:43
 *
 * @author [email protected]
 */
@Controller
@RequestMapping("/login")
public class LoginController {

    /**
     * loginCheck:ajax异步校验登录请求.
     *
     * @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
    }
}