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JustAPI

File Uploads

JustAPI provides robust support for file uploads via multipart/form-data using Rust’s multer parser, with streaming to temporary files to avoid memory exhaustion.

Basic File Upload

Section titled “Basic File Upload”
from justapi import JustAPIApp, UploadFile, File


app = JustAPIApp()




@app.post("/upload/")
async def upload_file(request, file: UploadFile = File(...)):
    return {
        "filename": file.filename,
        "content_type": file.content_type,
        "size": file.size,
    }
Terminal window
curl -X POST http://127.0.0.1:8000/upload/ \
  -F "file=@example.txt"
# Output: {"filename":"example.txt","content_type":"text/plain","size":1234}

Multiple Files

Section titled “Multiple Files”
@app.post("/upload-multiple/")
async def upload_multiple(request, files: list[UploadFile] = File(...)):
    return {
        "files": [
            {"name": f.filename, "size": f.size} for f in files
        ],
        "count": len(files),
    }
Terminal window
curl -X POST http://127.0.0.1:8000/upload-multiple/ \
  -F "files=@a.txt" \
  -F "files=@b.txt"

File + Form Fields Together

Section titled “File + Form Fields Together”
@app.post("/profile/")
async def create_profile(
    request,
    avatar: UploadFile = File(...),
    name: str = Form(...),
    bio: str = Form(""),
):
    return {
        "name": name,
        "bio": bio,
        "avatar_filename": avatar.filename,
        "avatar_size": avatar.size,
    }
Terminal window
curl -X POST http://127.0.0.1:8000/profile/ \
  -F "avatar=@photo.jpg" \
  -F "name=Alice" \
  -F "bio=Hello world"

The UploadFile Object

Section titled “The UploadFile Object”
Attribute/Method Type Description
filename str Original filename from the client
content_type str MIME type of the file
file str Path to the temporary file on disk
size int File size in bytes
.read() bytes Read file contents into memory

How It Works

Section titled “How It Works”
  1. The Rust multer parser streams multipart data as it arrives
  2. Each uploaded file is written to a temporary file on disk (not held in memory)
  3. The UploadFile Python object provides a zero-copy view of the file path
  4. Temporary files are cleaned up when the request completes

Asynchronous Processing

Section titled “Asynchronous Processing”

For large files, process asynchronously to avoid blocking:

import aiofiles
from justapi import UploadFile, File




@app.post("/process-large/")
async def process_large(request, file: UploadFile = File(...)):
    # Read and process in chunks
    content = await file.read()
    result = await process_content(content)
    return {"result": result}

Next Steps

Section titled “Next Steps”