add<验证码支持>

src/main/java/example/controller/CaptchaServlet.java

@@ -0,0 +1,64 @@
+package example.controller;
+
+import javax.servlet.ServletException;
+import javax.servlet.annotation.WebServlet;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+import java.awt.*;
+import java.awt.image.BufferedImage;
+import java.io.IOException;
+import java.io.OutputStream;
+import java.util.Random;
+
+@WebServlet("/captcha")
+public class CaptchaServlet extends HttpServlet {
+
+    // 处理生成验证码图片的请求
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
+        // 设置响应类型为图片
+        response.setContentType("image/jpeg");
+
+        // 设置验证码内容
+        String captchaText = generateCaptchaText();
+
+        // 将验证码存储到 session 中
+        request.getSession().setAttribute("captcha", captchaText);
+
+        // 创建验证码图片
+        BufferedImage image = new BufferedImage(100, 40, BufferedImage.TYPE_INT_RGB);
+        Graphics2D graphics = image.createGraphics();
+        graphics.setColor(Color.WHITE);
+        graphics.fillRect(0, 0, 100, 40);
+        graphics.setFont(new Font("Arial", Font.BOLD, 30));
+        graphics.setColor(Color.BLACK);
+        graphics.drawString(captchaText, 10, 30);
+
+        // 输出验证码图片
+        OutputStream out = response.getOutputStream();
+        javax.imageio.ImageIO.write(image, "JPEG", out);
+        out.close();
+    }
+
+    // 生成随机的验证码文本
+    private String generateCaptchaText() {
+        String characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+        StringBuilder captcha = new StringBuilder();
+        Random random = new Random();
+        for (int i = 0; i < 4; i++) {
+            int index = random.nextInt(characters.length());
+            captcha.append(characters.charAt(index));
+        }
+        return captcha.toString();
+    }
+
+    // 检查用户提交的验证码是否正确（忽略大小写）
+    public static boolean validateCaptcha(HttpServletRequest request, String userInputCaptcha) {
+        String sessionCaptcha = (String) request.getSession().getAttribute("captcha");
+        if (sessionCaptcha == null) {
+            return false; // 验证码已过期或不存在
+        }
+        return sessionCaptcha.equalsIgnoreCase(userInputCaptcha);
+    }
+}