make a media api, encapsulate the original S3 bucket address

there are 3 parts, from back to head, url inside the bucket -> url of backend media api -> backend domain, only the last part is spliced by frontend, the other two parts are spliced with sqlalchemy

app/media/router.py

@@ -0,0 +1,45 @@
+from fastapi import APIRouter, HTTPException
+from fastapi.responses import StreamingResponse
+import oss2
+from app.utils.s3 import bucket  
+
+router = APIRouter(prefix="/v1/media", tags=["Media"])
+
+@router.get("/{file_path:path}")
+async def get_avatar(file_path: str):
+    """
+    通过流式传输代理阿里云 OSS 中的图片
+    file_path 接收 avatars/xxx/avatar.jpg 等任何相对路径
+    """
+    s3_key = file_path.lstrip("/")
+    
+    if not s3_key:
+        raise HTTPException(status_code=400, detail="Invalid file path")
+        
+    try:
+        # 从阿里云 OSS 获取对象
+        # oss2 的 get_object 是同步阻塞的
+        # 初期可以直接用，后续高并发可以放入 run_in_executor
+        oss_object = bucket.get_object(s3_key)
+        
+        # 获取文件的 Content-Type
+        content_type = oss_object.headers.get("Content-Type", "image/jpeg")
+        
+        # 创建一个生成器来分块读取 OSS 数据，防止大文件时撑爆内存
+        def image_stream():
+            while True:
+                chunk = oss_object.read(1024 * 64)  # 每次读 64KB
+                if not chunk:
+                    break
+                yield chunk
+                
+        # 流式返回给前端
+        return StreamingResponse(image_stream(), media_type=content_type)
+        
+    except oss2.exceptions.NoSuchKey:
+        # 阿里云 OSS 专属的 404 异常
+        raise HTTPException(status_code=404, detail="Image not found in storage")
+    except Exception as e:
+        import traceback
+        traceback.print_exc()
+        raise HTTPException(status_code=500, detail="Internal storage service error")