feat: 头像文件存储到服务器

- 登录时自动下载微信头像到服务器
- 手动上传头像保存到服务器
- 数据库存储服务器上的头像路径
- 添加downloadAvatar方法处理头像下载

src/main/java/xuan/controller/UserController.java

@@ -10,6 +10,8 @@ import xuan.service.UserInfoService;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -64,7 +66,12 @@ public class UserController {
                 openId = "guest_" + System.currentTimeMillis();
             }
             
-            UserInfo user = userInfoService.loginOrRegister(openId, nickname, avatarUrl);
+            String localAvatarUrl = avatarUrl;
+            if (avatarUrl != null && !avatarUrl.isEmpty() && avatarUrl.startsWith("http")) {
+                localAvatarUrl = downloadAvatar(avatarUrl, openId);
+            }
+            
+            UserInfo user = userInfoService.loginOrRegister(openId, nickname, localAvatarUrl);
             
             Map<String, Object> data = new HashMap<>();
             data.put("id", user.getId());
@@ -88,6 +95,40 @@ public class UserController {
         return result;
     }
     
+    private String downloadAvatar(String imageUrl, String userId) {
+        try {
+            String uploadDir = "uploads/avatars/";
+            File dir = new File(uploadDir);
+            if (!dir.exists()) {
+                dir.mkdirs();
+            }
+            
+            String extension = ".jpg";
+            if (imageUrl.contains(".")) {
+                String tempExt = imageUrl.substring(imageUrl.lastIndexOf("."));
+                if (tempExt.contains("?")) {
+                    tempExt = tempExt.substring(0, tempExt.indexOf("?"));
+                }
+                if (tempExt.length() <= 5 && tempExt.matches("\\.[a-zA-Z]+")) {
+                    extension = tempExt;
+                }
+            }
+            
+            String filename = userId + "_" + System.currentTimeMillis() + extension;
+            Path filePath = Paths.get(uploadDir + filename);
+            
+            URL url = new URL(imageUrl);
+            try (InputStream in = url.openStream()) {
+                Files.copy(in, filePath);
+            }
+            
+            return "/uploads/avatars/" + filename;
+        } catch (Exception e) {
+            System.err.println("下载头像失败: " + e.getMessage());
+            return imageUrl;
+        }
+    }
+    
     @GetMapping("/info")
     public Map<String, Object> getUserInfo(@RequestParam String userId) {
         Map<String, Object> result = new HashMap<>();