How do I save a file to MongoDB?

Question

If your files are small enough (under 16 megabytes), instead of adding the complexity of GridFS, you can just embed the files into BSON documents.

BSON has a binary data type, to which any of the drivers should provide access.

If your file is a text file you can just store it as a UTF8 string.

To store files in MongoDB you should try to use GridFS.
You can find some tutorials about working with GridFS (example).
Check your MongoDB Driver's API and try to implement it in your project

When to Use GridFS

From official doc: https://docs.mongodb.com/manual/core/gridfs/#when-to-use-gridfs

In MongoDB, use GridFS for storing files larger than 16 MB.

In some situations, storing large files may be more efficient in a MongoDB database than on a system-level filesystem.

• If your filesystem limits the number of files in a directory, you can use GridFS to store as many files as needed.

• When you want to access information from portions of large files without having to load whole files into memory, you can use GridFS to recall sections of files without reading the entire file into memory.

• When you want to keep your files and metadata automatically synced and deployed across a number of systems and facilities, you can use GridFS. When using geographically distributed replica sets, MongoDB can distribute files and their metadata automatically to a number of mongod instances and facilities.

Do not use GridFS if you need to update the content of the entire file atomically. As an alternative you can store multiple versions of each file and specify the current version of the file in the metadata. You can update the metadata field that indicates “latest” status in an atomic update after uploading the new version of the file, and later remove previous versions if needed.

Furthermore, if your files are all smaller the 16 MB BSON Document Size limit, consider storing the file manually within a single document instead of using GridFS. You may use the BinData data type to store the binary data. See your drivers documentation for details on using BinData.