如果你想让请求处理器返回验证码信息，你可以在处理器函数中生成验证码，并将其作为响应返回给客户端。以下是一个简单的示例，使用 Spring WebFlux 框架生成一个包含随机生成的验证码的图片，并将其作为响应返回给客户端，代码如下所示。

import org.springframework.http.MediaType;
import org.springframework.web.reactive.function.server.RouterFunction;
import org.springframework.web.reactive.function.server.ServerRequest;
import org.springframework.web.reactive.function.server.ServerResponse;
import reactor.core.publisher.Mono;import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Random;import static org.springframework.web.reactive.function.server.RouterFunctions.route;
import static org.springframework.web.reactive.function.server.ServerResponse.ok;public class CaptchaHandler {public RouterFunction<ServerResponse> captchaRoute() {return route().GET("/captcha", this::generateCaptcha).build();}private Mono<ServerResponse> generateCaptcha(ServerRequest request) {// Generate random captcha stringString captcha = generateRandomCaptcha();// Generate captcha imageBufferedImage image = generateCaptchaImage(captcha);// Convert image to byte arrayByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();try {ImageIO.write(image, "png", byteArrayOutputStream);} catch (IOException e) {return ServerResponse.badRequest().build();}// Return image as responsereturn ok().contentType(MediaType.IMAGE_PNG).bodyValue(byteArrayOutputStream.toByteArray());}private String generateRandomCaptcha() {// Generate random captcha stringRandom random = new Random();StringBuilder captcha = new StringBuilder();for (int i = 0; i < 6; i++) {captcha.append((char) (random.nextInt(10) + '0')); // Random digit}return captcha.toString();}private BufferedImage generateCaptchaImage(String captcha) {// Generate captcha imageint width = 120;int height = 40;BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);Graphics2D graphics = image.createGraphics();// Set background colorgraphics.setColor(Color.WHITE);graphics.fillRect(0, 0, width, height);// Set text colorgraphics.setColor(Color.BLACK);graphics.setFont(new Font("Arial", Font.PLAIN, 20));// Draw captcha textgraphics.drawString(captcha, 20, 30);// Add noise (optional)// ...// Dispose graphicsgraphics.dispose();return image;}
}

  在这个示例中，generateCaptcha 方法生成一个随机的验证码字符串，然后generateCaptchaImage 方法使用生成的验证码字符串创建一个验证码图片。最后，使用 ServerResponse.ok().contentType(MediaType.IMAGE_PNG).bodyValue 将验证码图片作为响应返回给客户端。

  你可以将这个处理器注册到你的 Spring WebFlux 应用程序中，并在浏览器中访问 /captcha 路径来获取验证码图片。