Implement real async COS image upload

src/main/java/com/openisle/controller/UserController.java

@@ -29,7 +29,7 @@ public class UserController {
     @PostMapping("/me/avatar")
     public ResponseEntity<?> uploadAvatar(@RequestParam("file") MultipartFile file,
                                           Authentication auth) throws IOException {
-        String url = imageUploader.upload(file.getBytes(), file.getOriginalFilename());
+        String url = imageUploader.upload(file.getBytes(), file.getOriginalFilename()).join();
         userService.updateAvatar(auth.getName(), url);
         return ResponseEntity.ok(Map.of("url", url));
     }

src/main/java/com/openisle/service/CosImageUploader.java

@@ -1,24 +1,66 @@
 package com.openisle.service;
 
+import com.qcloud.cos.COSClient;
+import com.qcloud.cos.ClientConfig;
+import com.qcloud.cos.auth.BasicCOSCredentials;
+import com.qcloud.cos.auth.COSCredentials;
+import com.qcloud.cos.model.ObjectMetadata;
+import com.qcloud.cos.model.PutObjectRequest;
+import com.qcloud.cos.region.Region;
 import org.springframework.beans.factory.annotation.Value;
+import org.springframework.scheduling.concurrent.CustomizableThreadFactory;
 import org.springframework.stereotype.Service;
 
+import java.io.ByteArrayInputStream;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
 /**
  * ImageUploader implementation using Tencent Cloud COS.
- * For simplicity this demo just returns a URL composed of the base URL and file name.
  */
 @Service
 public class CosImageUploader extends ImageUploader {
 
+    private final COSClient cosClient;
+    private final String bucketName;
     private final String baseUrl;
+    private final ExecutorService executor = Executors.newFixedThreadPool(2,
+            new CustomizableThreadFactory("cos-upload-"));
 
-    public CosImageUploader(@Value("${cos.base-url:https://example.com}") String baseUrl) {
+    @org.springframework.beans.factory.annotation.Autowired
+    public CosImageUploader(
+            @Value("${cos.secret-id:}") String secretId,
+            @Value("${cos.secret-key:}") String secretKey,
+            @Value("${cos.region:ap-guangzhou}") String region,
+            @Value("${cos.bucket-name:}") String bucketName,
+            @Value("${cos.base-url:https://example.com}") String baseUrl) {
+        COSCredentials cred = new BasicCOSCredentials(secretId, secretKey);
+        ClientConfig config = new ClientConfig(new Region(region));
+        this.cosClient = new COSClient(cred, config);
+        this.bucketName = bucketName;
+        this.baseUrl = baseUrl;
+    }
+
+    // for tests
+    CosImageUploader(COSClient cosClient, String bucketName, String baseUrl) {
+        this.cosClient = cosClient;
+        this.bucketName = bucketName;
         this.baseUrl = baseUrl;
     }
 
     @Override
-    public String upload(byte[] data, String filename) {
-        // In a real implementation you would call COS SDK here
-        return baseUrl + "/" + filename;
+    public CompletableFuture<String> upload(byte[] data, String filename) {
+        return CompletableFuture.supplyAsync(() -> {
+            ObjectMetadata meta = new ObjectMetadata();
+            meta.setContentLength(data.length);
+            PutObjectRequest req = new PutObjectRequest(
+                    bucketName,
+                    filename,
+                    new ByteArrayInputStream(data),
+                    meta);
+            cosClient.putObject(req);
+            return baseUrl + "/" + filename;
+        }, executor);
     }
 }

src/main/java/com/openisle/service/ImageUploader.java

@@ -10,5 +10,10 @@ public abstract class ImageUploader {
      * @param filename name of the file
      * @return accessible URL of the uploaded file
      */
-    public abstract String upload(byte[] data, String filename);
+    /**
+     * Upload an image asynchronously and return a future of its accessible URL.
+     * Implementations should complete the future exceptionally on failures so
+     * callers can react accordingly.
+     */
+    public abstract java.util.concurrent.CompletableFuture<String> upload(byte[] data, String filename);
 }