Java生成图片验证码

Java生成图片验证码
部分代码参考自网易博客白云城主的大作
制作一个Servlet实现验证码功能

response.setContentType("image/jpeg");
	        response.setHeader("Pragma","No-cache");
	        response.setHeader("Cache-Control","no-cache");
	        response.setDateHeader("Expires", 0);      
	        HttpSession session=request.getSession();
	        // 在内存中创建图象
	        int width=60, height=20;
	        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
	        // 获取图形上下文
	        Graphics g = image.getGraphics();
	        //生成随机类
	        Random random = new Random();
	        // 设定背景色
	        g.setColor(getRandColor(200,250));
	        g.fillRect(0, 0, width, height);
	        //设定字体
	        g.setFont(new Font("Times New Roman",Font.PLAIN,18));
	        //画边框
	        //g.setColor(new Color());
	        //g.drawRect(0,0,width-1,height-1);
	        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
	        g.setColor(getRandColor(160,200));
	        for (int i=0;i<155;i++) {
	            int x = random.nextInt(width);
	            int y = random.nextInt(height);
	            int xl = random.nextInt(12);
	            int yl = random.nextInt(12);
	            g.drawLine(x,y,x+xl,y+yl);
	        }
	        // 取随机产生的认证码(4位数字)
	        String sRand="";
	        for (int i=0;i<6;i++){
	            String rand=String.valueOf(random.nextInt(10));
	            sRand+=rand;
	            // 将认证码显示到图象中
	            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
	            g.drawString(rand,13*i+6,16);
	        }
	        // 将认证码存入SESSION
	        session.setAttribute("rand",sRand);
	        // 图象生效
	        g.dispose();
	        ServletOutputStream responseOutputStream =response.getOutputStream();
	        // 输出图象到页面
	        ImageIO.write(image, "JPEG", responseOutputStream);
	        //以下关闭输入流！
	        responseOutputStream.flush();
	        responseOutputStream.close();

 有一个辅助方法,用以分配随机颜色

 Color getRandColor(int fc,int bc){//给定范围获得随机颜色
	        Random random = new Random();
	        if(fc>255) fc=255;
	        if(bc>255) bc=255;
	        int r=fc+random.nextInt(bc-fc);
	        int g=fc+random.nextInt(bc-fc);
	        int b=fc+random.nextInt(bc-fc);
	        return new Color(r,g,b);
	    }

 在页面上显示验证码只需

 

 <img 
    style="cursor:hand" title="单击换图"
    onclick="this.src='<%=basePath %>/servlet/getCaptcha'"
    src="<%=basePath %>/servlet/getCaptcha"><br>

 用户登录时,再session中取得正确的验证码进行比对,如果想换成字母的,自己可以稍加修改

 

 

PHP中实现验证码有很多开源的类库,java也不例外,我找了一个,做一下测试,simplecaptcha-1.2-jdk1.5.jar

支持三种验证码,不需写任何代码..验证码在Session中存储的名字为Captcha.NAME常量
以servlet提供,需要在web.xml中配置

<servlet>
        <servlet-name>AudioCaptcha</servlet-name>
        <servlet-class>nl.captcha.servlet.AudioCaptchaServlet</servlet-class>
    </servlet>

	<servlet>
		<servlet-name>SimpleCaptcha</servlet-name>
		<servlet-class>nl.captcha.servlet.SimpleCaptchaServlet</servlet-class>
        <init-param>
            <param-name>captcha-width</param-name>
            <param-value>300</param-value>
        </init-param>
        <init-param>
            <param-name>captcha-height</param-name>
            <param-value>100</param-value>
        </init-param>
	</servlet>
	
    <servlet>
		<servlet-name>StickyCaptcha</servlet-name>
		<servlet-class>nl.captcha.servlet.StickyCaptchaServlet</servlet-class>

        <init-param>
            <!-- Optional; defaults to 200. -->
            <param-name>captcha-width</param-name>
            <param-value>250</param-value>
        </init-param>
        <init-param>
            <!-- Optional; defaults to 50. -->
            <param-name>captcha-height</param-name>
            <param-value>75</param-value>
        </init-param>
        <init-param>
            <!-- Time To Live, in ms. Optional; Defaults to 600000ms. -->
            <param-name>ttl</param-name>
            <param-value>100000</param-value>
        </init-param>
    </servlet>

	<servlet-mapping>
		<servlet-name>AudioCaptcha</servlet-name>
		<url-pattern>/audio.wav</url-pattern>
	</servlet-mapping>
	<servlet-mapping>
		<servlet-name>SimpleCaptcha</servlet-name>
		<url-pattern>/simpleCaptcha.png</url-pattern>
	</servlet-mapping>
	<servlet-mapping>
		<servlet-name>StickyCaptcha</servlet-name>
		<url-pattern>/stickyCaptcha.png</url-pattern>
	</servlet-mapping>

 simpleCaptcha是一种简单的验证码,5位字母或数字,刷新一下变一次
StickyCaptcha也是一种简单的验证码,但是刷新不变
audio是音频的验证码,没测试..以单独的Session存储,名字AudioCaptcha.NAME