要防止防爬虫、外挂等软件自动登录或者刷票，验证码和校验方式肯定不能再前台完成，如果在前台完成，只要程序猿解读了客户端获取和校验的方式，大门就如同虚设。
其实思路很简单，操作如下：
- 在后台生成验证码和验证码图片。
- 通过Redis或者关系库，存储验证码和验证码对应的唯一标识（如：uuid）
- 将验证图片和唯一标识返给前端（这样，前端就没有验证码信息了，只有一个小图片）
- 验证：将用户根据图片输入的验证码和唯一标识返给后端，通过唯一标识取出验证码和用户输入的比对。
代码如下：
验证码工具类：VerifyCodeUtils
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Random;
import javax.imageio.ImageIO;
/**
* 验证码工具类
*/
public class VerifyCodeUtils
{
// 使用到Algerian字体，系统里没有的话需要安装字体，字体只显示大写，去掉了1,0,i,o几个容易混淆的字符
public static final String VERIFY_CODES = "123456789ABCDEFGHJKLMNPQRSTUVWXYZ";
private static Random random = new SecureRandom();
/**
* 使用系统默认字符源生成验证码
* @param verifySize 验证码长度
* @return
*/
public static String generateVerifyCode(int verifySize)
{
return generateVerifyCode(verifySize, VERIFY_CODES);
}
/**
* 使用指定源生成验证码
* @param verifySize 验证码长度
* @param sources 验证码字符源
* @return
*/
public static String generateVerifyCode(int verifySize, String sources)
{
if (sources == null || sources.length() == 0)
{
sources = VERIFY_CODES;
}
int codesLen = sources.length();
Random rand = new Random(System.currentTimeMillis());
StringBuilder verifyCode = new StringBuilder(verifySize);
for (int i = 0; i < verifySize; i++)
{
verifyCode.append(sources.charAt(rand.nextInt(codesLen - 1)));
}
return verifyCode.toString();
}
/**
* 输出指定验证码图片流
* @param w
* @param h
* @param os
* @param code
* @throws IOException
*/
public static void outputImage(int w, int h, OutputStream os, String code) throws IOException
{
int verifySize = code.length();
BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
Random rand = new Random();
Graphics2D g2 = image.createGraphics();
g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
Color[] colors = new Color[5];
Color[] colorSpaces = new Color[] {
Color.WHITE, Color.CYAN, Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA,
Color.ORANGE, Color.PINK, Color.YELLOW };
float[] fractions = new float[colors.length];
for (int i = 0; i < colors.length; i++)
{
colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)];
fractions[i] = rand.nextFloat();
}
Arrays.sort(fractions);
g2.setColor(Color.GRAY);// 设置边框色
g2.fillRect(0, 0, w, h);
Color c = getRandColor(200, 250);
g2.setColor(c);// 设置背景色
g2.fillRect(0, 2, w, h - 4);
// 绘制干扰线
Random random = new Random();
g2.setColor(getRandColor(160, 200));// 设置线条的颜色
for (int i = 0; i < 20; i++)
{
int x = random.nextInt(w - 1);
int y = random.nextInt(h - 1);
int xl = random.nextInt(6) + 1;
int yl = random.nextInt(12) + 1;
g2.drawLine(x, y, x + xl + 40, y + yl + 20);
}
// 添加噪点
float yawpRate = 0.05f;// 噪声率
int area = (int) (yawpRate * w * h);
for (int i = 0; i < area; i++)
{
int x = random.nextInt(w);
int y = random.nextInt(h);
int rgb = getRandomIntColor();
image.setRGB(x, y, rgb);
}
shear(g2, w, h, c);// 使图片扭曲
g2.setColor(getRandColor(100, 160));
int fontSize = h - 4;
Font font = new Font("Algerian", Font.ITALIC, fontSize);
g2.setFont(font);
char[] chars = code.toCharArray();
for (int i = 0; i < verifySize; i++)
{
AffineTransform affine = new AffineTransform();
affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1),
(w / verifySize) * i + fontSize / 2, h / 2);
g2.setTransform(affine);
g2.drawChars(chars, i, 1, ((w - 10) / verifySize) * i + 5, h / 2 + fontSize / 2 - 10);
}
g2.dispose();
ImageIO.write(image, "jpg", os);
}
private static Color getRandColor(int fc, int bc)
{
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);
}
private static int getRandomIntColor()
{
int[] rgb = getRandomRgb();
int color = 0;
for (int c : rgb)
{
color = color << 8;
color = color | c;
}
return color;
}
private static int[] getRandomRgb()
{
int[] rgb = new int[3];
for (int i = 0; i < 3; i++)
{
rgb[i] = random.nextInt(255);
}
return rgb;
}
private static void shear(Graphics g, int w1, int h1, Color color)
{
shearX(g, w1, h1, color);
shearY(g, w1, h1, color);
}
private static void shearX(Graphics g, int w1, int h1, Color color)
{
int period = random.nextInt(2);
boolean borderGap = true;
int frames = 1;
int phase = random.nextInt(2);
for (int i = 0; i < h1; i++)
{
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames);
g.copyArea(0, i, w1, 1, (int) d, 0);
if (borderGap)
{
g.setColor(color);
g.drawLine((int) d, i, 0, i);
g.drawLine((int) d + w1, i, w1, i);
}
}
}
private static void shearY(Graphics g, int w1, int h1, Color color)
{
int period = random.nextInt(40) + 10; // 50;
boolean borderGap = true;
int frames = 20;
int phase = 7;
for (int i = 0; i < w1; i++)
{
double d = (double) (period >> 1)
* Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames);
g.copyArea(i, 0, 1, h1, 0, (int) d);
if (borderGap)
{
g.setColor(color);
g.drawLine(i, (int) d, i, 0);
g.drawLine(i, (int) d + h1, i, h1);
}
}
}
}
前端请求验证码图片代码，此时使用redis存储验证码临时信息，涉及类较多，代码仅供参考，主要体现是思想。
/**
* 验证码操作处理
*/
@RestController
public class CaptchaController
{
@Autowired
private RedisCache redisCache;
/**
* 生成验证码
*/
@GetMapping("/captchaImage")
public AjaxResult getCode(HttpServletResponse response) throws IOException
{
// 生成随机字串
String verifyCode = VerifyCodeUtils.generateVerifyCode(4);
// 唯一标识
String uuid = IdUtils.simpleUUID();
//Constants.CAPTCHA_CODE_KEY 添加前缀，方便取数时能快速检索
String verifyKey = Constants.CAPTCHA_CODE_KEY + uuid;
//CAPTCHA_EXPIRATION 验证码有效期 单位 MINUTES 分钟
redisCache.setCacheObject(verifyKey, verifyCode, Constants.CAPTCHA_EXPIRATION, TimeUnit.MINUTES);
// 生成图片
int w = 111, h = 36;
ByteArrayOutputStream stream = new ByteArrayOutputStream();
VerifyCodeUtils.outputImage(w, h, stream, verifyCode);
try
{
AjaxResult ajax = AjaxResult.success();
ajax.put("uuid", uuid);
ajax.put("img", Base64.encode(stream.toByteArray()));
return ajax;
}
catch (Exception e)
{
e.printStackTrace();
return AjaxResult.error(e.getMessage());
}
finally
{
stream.close();
}
}
}
验证时的伪代码：
public String login(String username, String password, String code, String uuid)
{
String verifyKey = Constants.CAPTCHA_CODE_KEY + uuid;
String captcha = redisCache.getCacheObject(verifyKey);
if (captcha == null)
[
throw new CaptchaExpireException();
}
if (!code.equalsIgnoreCase(captcha))
{
throw new CaptchaException();
}
}
OK，到这大功告成！！