java实现验证码完整版详解编程语言

第一步：在web.xml中配置servlet

    <servlet>   
        <servlet-name>ImageServlet</servlet-name>   
        <servlet-class>org.servlet.ImageServlet</servlet-class>   
    </servlet>   
    <servlet-mapping>   
        <servlet-name>ImageServlet</servlet-name>   
        <url-pattern>/ImageServlet</url-pattern>   
    </servlet-mapping>  

第二步： ImageServlet 实现

    import javax.servlet.ServletException;   
    import javax.servlet.http.HttpServlet;   
    import javax.servlet.http.HttpServletRequest;   
    import javax.servlet.http.HttpServletResponse;   
       
    import com.farm.web.tool.RandomValidateCode;   
       
    public class ImageServlet extends HttpServlet {   
       
        private static final long serialVersionUID = 1L;   
       
        public void doGet(HttpServletRequest request, HttpServletResponse response)   
                throws ServletException, IOException {   
       
            response.setContentType("image/jpeg");// 设置相应类型,告诉浏览器输出的内容为图片   
            response.setHeader("Pragma", "No-cache");// 设置响应头信息，告诉浏览器不要缓存此内容   
            response.setHeader("Cache-Control", "no-cache");   
            response.setDateHeader("Expire", 0);   
            RandomValidateCode randomValidateCode = new RandomValidateCode();   
            try {   
                randomValidateCode.getRandcode(request, response);// 输出图片方法   
            } catch (Exception e) {   
                e.printStackTrace();   
            }   
        }   
       
        public void doPost(HttpServletRequest request, HttpServletResponse response)   
                throws ServletException, IOException {   
            doGet(request, response);   
        }   
       
    }  

    import java.awt.Color;   
    import java.awt.Font;   
    import java.awt.Graphics;   
    import java.awt.image.BufferedImage;   
    import java.util.Random;   
       
    import javax.imageio.ImageIO;   
    import javax.servlet.http.HttpServletRequest;   
    import javax.servlet.http.HttpServletResponse;   
    import javax.servlet.http.HttpSession;   
       
    public class RandomValidateCode {   
       
        public static String validateCode = null;   
        public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";// 放到session中的key   
        private Random random = new Random();   
        private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";// 随机产生的字符串   
       
        private int width = 80;// 图片宽   
        private int height = 26;// 图片高   
        private int lineSize = 40;// 干扰线数量   
        private int stringNum = 4;// 随机产生字符数量   
       
        /*  
         * 获得字体  
         */   
        private Font getFont() {   
            return new Font("Fixedsys", Font.CENTER_BASELINE, 18);   
        }   
       
        /*  
         * 获得颜色  
         */   
        private Color getRandColor(int fc, int bc) {   
            if (fc > 255)   
                fc = 255;   
            if (bc > 255)   
                bc = 255;   
            int r = fc + random.nextInt(bc - fc - 16);   
            int g = fc + random.nextInt(bc - fc - 14);   
            int b = fc + random.nextInt(bc - fc - 18);   
            return new Color(r, g, b);   
        }   
       
        /**  
         * 生成随机图片  
         */   
        public void getRandcode(HttpServletRequest request,   
                HttpServletResponse response) {   
            HttpSession session = request.getSession();   
            // BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类   
            BufferedImage image = new BufferedImage(width, height,   
                    BufferedImage.TYPE_INT_BGR);   
            Graphics g = image.getGraphics();// 产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作   
            g.fillRect(0, 0, width, height);   
            g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));   
            g.setColor(getRandColor(110, 133));   
            // 绘制干扰线   
            for (int i = 0; i <= lineSize; i++) {   
                drowLine(g);   
            }   
            // 绘制随机字符   
            String randomString = "";   
            for (int i = 1; i <= stringNum; i++) {   
                randomString = drowString(g, randomString, i);   
            }   
            session.removeAttribute(RANDOMCODEKEY);   
            session.setAttribute(RANDOMCODEKEY, randomString);   
            validateCode = randomString.toUpperCase();   
            g.dispose();   
            try {   
                ImageIO.write(image, "JPEG", response.getOutputStream());// 将内存中的图片通过流动形式输出到客户端   
            } catch (Exception e) {   
                e.printStackTrace();   
            }   
        }   
       
        /*  
         * 绘制字符串  
         */   
        private String drowString(Graphics g, String randomString, int i) {   
            g.setFont(getFont());   
            g.setColor(new Color(random.nextInt(101), random.nextInt(111), random   
                    .nextInt(121)));   
            String rand = String.valueOf(getRandomString(random.nextInt(randString   
                    .length())));   
            randomString += rand;   
            g.translate(random.nextInt(3), random.nextInt(3));   
            g.drawString(rand, 13 * i, 16);   
            return randomString;   
        }   
       
        /*  
         * 绘制干扰线  
         */   
        private void drowLine(Graphics g) {   
            int x = random.nextInt(width);   
            int y = random.nextInt(height);   
            int xl = random.nextInt(13);   
            int yl = random.nextInt(15);   
            g.drawLine(x, y, x + xl, y + yl);   
        }   
       
        /*  
         * 获取随机的字符  
         */   
        public String getRandomString(int num) {   
            return String.valueOf(randString.charAt(num));   
        }   
    }  

第三步：jsp展现

    <tr>   
        <td>   
            <div align="right">   
                验证码：   
            </div>   
        </td>   
        <td>   
            <input style="width: 65px" id="validatecode" name="validatecode" type="text" />   
        </td>   
        <td>   
            <img title="看不清楚,换一张？" style="cursor: pointer;"   
                onclick="javascript:refresh(this);"   
                src="<PF:basePath/>/ImageServlet">   
        </td>   
    </tr>  

src路径根据情况修改

    function refresh(obj) {   
        obj.src = "<PF:basePath/>/ImageServlet?"+Math.random();     
    }  

第四步：Action验证

if(RandomValidateCode.validateCode!=null&&validatecode.trim().toUpperCase().equals(RandomValidateCode.validateCode)){   
    System.out.println("验证码正确");   
}