feat: create class util security captcha implements

pom.xml

@@ -108,6 +108,12 @@
 			<artifactId>spring-boot-starter-test</artifactId>
 			<scope>test</scope>
 		</dependency>
+
+        <dependency>
+            <groupId>cn.apiclub.tool</groupId>
+            <artifactId>simplecaptcha</artifactId>
+            <version>1.2.2</version>
+        </dependency>
 	</dependencies>
 
 	<build>

src/main/java/com/example/spring_boot_project/Security/CaptchaUtil.java

@@ -0,0 +1,28 @@
+package com.example.spring_boot_project.Security;
+
+import cn.apiclub.captcha.Captcha;
+
+import javax.imageio.ImageIO;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Base64;
+
+public class CaptchaUtil {
+    public static Captcha createCaptcha(int width, int height){
+        return new Captcha.Builder(width, height)
+                .addText()
+                .addBackground()
+                .addNoise()
+                .build();
+    }
+
+    public static String encodeCaptcha(Captcha c){
+        try(ByteArrayOutputStream o = new ByteArrayOutputStream()){
+            ImageIO.write(c.getImage(), "jpg", o);
+            return Base64.getEncoder().encodeToString(o.toByteArray());
+        } catch (IOException e){
+            throw new RuntimeException("error encoding Captcha", e);
+        }
+    }
+
+}

src/main/java/com/example/spring_boot_project/controller/AuthController.java

@@ -28,14 +28,17 @@ public AuthController(UserService userService, BCryptPasswordEncoder passwordEnc
     @PostMapping("/register")
     public ResponseEntity<?> registerUser(@RequestBody RegisterRequest request) {
         Optional<User> existingUser = userService.findByUsername(request.getUsername());
+
         if (existingUser.isPresent()) {
             return ResponseEntity.badRequest().body("Username already exists.");
         }
+
         User user = new User();
         user.setUsername(request.getUsername());
         user.setPassword(passwordEncoder.encode(request.getPassword()));
         user.setRole("USER");
         userService.save(user);
+
         return ResponseEntity.ok().body("User registered successfully");
     }
 
@@ -53,6 +56,7 @@ public ResponseEntity<?> loginUser(@RequestBody Map<String, String> request) {
                 passwordEncoder.matches(rawPassword, userOptional.get().getPassword())) {
 
             String token = jwtUtil.generateToken(userOptional.get().getUsername());
+
             return ResponseEntity.ok(Map.of("token", token));
         }