kaptcha生成java验证码

kaptcha工作的原理是调用 com.google.code.kaptcha.servlet.KaptchaServlet，生成一个图片。同时将生成的验证码字符串放到 HttpSession中。

1：前期工作：准备kaptcha的jar包

 <!--kaptcha-->
    <dependency>
      <groupId>com.github.axet</groupId>
      <artifactId>kaptcha</artifactId>
      <version>0.0.9</version>
    </dependency>

2：在spring配置文件中配置图片生成器的bean

  <bean id="captchaProducer" class="com.google.code.kaptcha.impl.DefaultKaptcha">
        <property name="config">
            <bean class="com.google.code.kaptcha.util.Config">
                <constructor-arg>
                    <props>
                        <prop key="kaptcha.border">no</prop>
                        <prop key="kaptcha.border.color">105,179,90</prop>
                        <prop key="kaptcha.textproducer.font.color">red</prop>
                        <prop key="kaptcha.image.width">250</prop>
                        <prop key="kaptcha.textproducer.font.size">80</prop>
                        <prop key="kaptcha.image.height">90</prop>
                        <prop key="kaptcha.session.key">code</prop>
                        <prop key="kaptcha.textproducer.char.length">4</prop>
                        <prop key="kaptcha.textproducer.font.names">宋体,楷体,微软雅黑</prop>
                    </props>
                </constructor-arg>
            </bean>
        </property>
    </bean>

里面配置了很多图片生成器的属性，比如字体颜色，字体大小等，根据英文意思就能理解大概配置的是什么内容了

3：生成图片的控制器

@Controller
public class CaptchaImageCreateController {
    @Autowired
    private Producer captchaProducer;//验证码生成器

    @RequestMapping("/captcha-image")
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        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);//将生成的验证码保存在session中
        // 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;
    }
}

4.验证码验证控制器

@Controller
public class VerifyController {
    @RequestMapping(value = "/checkVerificationCode")
    @ResponseBody
    public boolean checkVerificationCode(@RequestParam("verifyCode")String verifyCode,
                                         HttpServletRequest request){
        //验证码的值
        String kaptchaExpected = (String)request.getSession()
                .getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
        //用户输入的验证码的值
        String kaptchaReceived = verifyCode;
        System.out.println("实际的验证码为："+kaptchaExpected);
        System.out.println("输入的验证码为："+kaptchaReceived);
        if(kaptchaReceived == null  || !kaptchaReceived.equalsIgnoreCase(kaptchaExpected)) {
            return false;
        }
        return true;
    }
}

期待输入的验证码从session中取出，和实际输入的验证码进行比较，如果相同，则返回true,否则返回false

5:前端页面

<div class="title"> 用户登录 </div>
<div class="loginbox">

    <form id="loginForm" action="/checkVerificationCode" method="post">
        <div style="height:40px;">
            <label class="tip">登 录 名:   </label>
            <input name="name" type="text" id="name" class="user-text" value="" />
        </div>
        <div style="height:40px;">
            <label class="tip">密   码：  </label>
            <input type="password" id="password" name="password" class="user-text" value="" />
        </div>
        <div style="height:60px;">
            <label class="tip">验 证 码:   </label>
            <input type="text" name="verifyCode" id="verifyCode" class="usertext" value="" />
            onchange="changeVerifyCode();"/>
            <img src="captcha-image.jpg" width="110" height="30" id="kaptchaImage"
                 style="margin-bottom: -13px"/>
        </div>
        <div style="margin-left:15px">
            <input type="submit" class="login-btn" value="登录" />
            <input type="reset"  class="login-btn" style="margin-left:10px;"  value="重置" />
        </div>
    </form>

</div>

　src="captcha-image.jpg",将触发生成图片的控制器，返回一张图片,action="/checkVerificationCode",将调用验证验证码的控制器，返回相应的结果。