web工程中登录验证码的实现

1.新建工具类CaptchaUtils，以下验证码生成方法是从网上找的一版普通的字母生成。

package com.shuaibiao.base.utils.captcha;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;

public class CaptchaUtils {

    // 图片的宽度。
    private int width = 160;
    // 图片的高度。
    private int height = 40;
    // 验证码字符个数
    private int codeCount = 5;
    // 验证码干扰线数
    private int lineCount = 150;
    // 验证码
    private String code = null;
    private char[] codeSequence = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R',
            'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
    private BufferedImage bufferedImage;

    private CaptchaUtils(int width, int height) {
        this.width = width;
        this.height = height;
    }

    public CaptchaUtils(int width, int height, int codeCount, int lineCount) {
        this(width, height);
        this.codeCount = codeCount;
        this.lineCount = lineCount;
        createCodeImage();
    }

    private void createCodeImage() {
        // 字符所在x坐标
        int x = 0;
        // 字体高度
        int fontHeight = 0;
        // 字符所在y坐标
        int codeY = 0;
        int red = 0;
        int green = 0;
        int blue = 0;
        x = width / (codeCount + 2);
        fontHeight = height - 2;
        codeY = height - 4;
        bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        Graphics2D graphics2D = bufferedImage.createGraphics();
        Random random = new Random();
        graphics2D.setColor(Color.WHITE);
        graphics2D.fillRect(0, 0, width, height);
        Font font = new Font("Fixedays", Font.PLAIN, fontHeight);
        graphics2D.setFont(font);
        for (int i = 0; i < lineCount; i++) {
            // x轴第一个点的位置
            int x1 = random.nextInt(width);
            // y轴第一个点的位置
            int y1 = random.nextInt(height);
            // x轴第二个点的位置
            int x2 = x1 + random.nextInt(width >> 2);
            // y轴第二个点的位置
            int y2 = y1 + random.nextInt(height >> 2);
            red = random.nextInt(255);
            green = random.nextInt(255);
            blue = random.nextInt(255);
            graphics2D.setColor(new Color(red, green, blue));
            graphics2D.drawLine(x1, y1, x2, y2);
        }
        StringBuffer randomCode = new StringBuffer(codeCount);
        for (int i = 0; i < codeCount; i++) {
            String strRand = String.valueOf(codeSequence[random.nextInt(codeSequence.length)]);
            red = random.nextInt(255);
            green = random.nextInt(255);
            blue = random.nextInt(255);
            graphics2D.setColor(new Color(red, green, blue));
            graphics2D.drawString(strRand, (i + 1) * x, codeY);
            randomCode.append(strRand);
        }
        code = randomCode.toString();
    }

    public void write(String path) throws IOException {
        OutputStream outputStream = new FileOutputStream(path);
        this.write(outputStream);
        outputStream.flush();
        outputStream.close();
    }

    public void write(OutputStream outputStream) throws IOException {
        ImageIO.write(bufferedImage, "png", outputStream);
    }

    public BufferedImage getBufferedImage() {
        return bufferedImage;
    }

    public String getCode() {
        return code;
    }

}

2.controller中请求方法

@RequestMapping("/captcha")
        public void generate(HttpServletRequest request, HttpServletResponse response){
              response.setContentType("image/jpeg");
              //禁止图像缓存       
              response.setHeader("Pragma","no-cache");
              response.setHeader("Cache-Control", "no-cache"); 
              response.setDateHeader("Expires", 0);     
              HttpSession session = request.getSession();  
              CaptchaUtils captchaUtils = new CaptchaUtils(120, 40, 5,30); 
              session.setAttribute("code", captchaUtils.getCode());      
              try {
                captchaUtils.write(response.getOutputStream());
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }                 
        }

3.需要用到验证码的地方，用Img标签src加入请求路径即可。

 <img src="/captcha" class="layadmin-user-login-codeimg" id="LAY-user-get-vercode">

4.登录过程中，从session中取出验证码与填写的request域中的验证码做比对，即可体现验证码的作用。

5.效果如下