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Multer ​

Empack provides first-class integration with @fastify/multipart to handle file uploads via a simple decorator-based API. Instead of registering multer manually for each route, you can simply use the @UseMultipart() decorator to enable upload support on any controller method.

Basic Usage ​

1. Handle single file upload ​

ts
@Post("/upload")
@UseMultipart()
uploadAvatar(@FromFile() file: FilePart) {
  return Responses.OK(`Uploaded: ${file.originalname}`);
}

2. Handle multiple files (array) ​

ts
@Post("/images")
@UseMultipart()
uploadImages(@FromFiles() files: FilePart[]) {
  return Responses.OK(`Uploaded ${files.length} files.`);
}

Default Behavior and Overrides ​

You can define global default Multer options using:

ts
app.setMulterDefaults({
  limits?: {
    fileSize?: number;
    files?: number;
  };
});

These defaults will be applied to all routes unless overridden. If a route is decorated with @UseMultipart(...), its options will override the defaults for that specific route only.

About @UseMultipart() and @FromMultipart() ​

The @UseMultipart() decorator configures the Multer middleware for parsing multipart/form-data in a route.

The @FromMultipart() decorator then allows you to inject a combined object that includes:

  • All text fields (req.body)
  • The uploaded files specified in @UseMultipart(), merged by their field names

NOTE

This means @FromMultipart() gives you a complete view of both form fields and uploaded files in one object.

Example ​

ts
@Post("/profile")
@UseMultipart()
updateProfile(
  @FromMultipart() body: {
    username: string;
    avatar?: FilePart;
    documents?: FilePart[];
  },
) {
  return Responses.OK(body);
}

This will result in an injected object like:

json
{
  username: "Alice",
  avatar: { filename: "pic.png", ... },
  documents: [{ filename: "doc1.pdf", ... }, { filename: "doc2.pdf", ... }]
}