/RethinkDB Java

Storing binary objects

This document has not been fully updated for Java. The API documentation for Java is complete, but many ReQL articles still have examples in other languages. We’ll be updating each article after the Java driver is officially released.

RethinkDB supports a native binary object type, letting you use ReQL to store binary objects directly in the database. The ReQL driver will transparently translate between the ReQL type and bytes.

For these examples, we’ll assume that the RethinkDB connection is available in class scope as conn.

Storing uploaded files in the database

It’s a common task for web applications to accept file uploads from users; with RethinkDB you can store these files directly in the database.

import java.io.file.*;

 * Store a file in the database.
 * @param filePath  the path to the file to save
 * @param saveName  the filename to store with the file in the database
 * @param userId    user ID value
public void saveFile(String[] filePath, String[] saveName, long userId) {
    byte[] fileData = Files.readAllBytes(filePath);
        r.hashMap("userId", userId)
         .with("filename", saveName)
         .with("file", r.binary(fileData))

In saveFile, we pass a path to the uploaded file (which may be in a temporary storage directory, even with a temporary name depending on the uploading library we’ve used), the name to save the file with, and the id of the user who’s uploaded the file. The binary ReQL command is used to store the file’s contents as a binary object in the file field.

def get_user_file_ids(user_id):
    Retrieve the IDs of previously-saved files for a user as a list of
    dicts: [{'id': x, 'filename': y}, ...]
    return r.table('files').filter({'user_id': user_id}).pluck(
        'id', 'filename').run(conn)

def get_file(file_id):
    Retrieve a file by its ID. Returns a dict with 'filename' and 'file'
    return r.table('files').get(file_id).pluck('file', 'filename').run(conn)

Then, there are two functions for retrieving files: one to retrieve a directory of a user’s uploaded files (get_user_file_ids) and one to retrieve the actual file itself (get_file). We don’t have to use binary again here; the ReQL driver will return the proper data type for the file field in our object.

Storing user avatars

Here’s another, more fun example: adding Gravatar avatars to user accounts. We can use http to retrieve them.

import hashlib

def add_gravatar(user_id):
    Add a gravatar field with the binary avatar icon to user accounts if they
    have an avatar associated with their email address.
    email = r.table('users').get(user_id)['email'].run(conn)
    hash = hashlib.md5(email).hexdigest()
    gravatar_url = 'http://www.gravatar.com/avatar/' + hash + '?d=retro'
        'gravatar': r.http(gravatar_url, result_format='binary')}).run(conn)

Where’s r.binary? You don’t need it in this case, because r.http will return a binary object with the result_format='binary' option. (If the MIME type on the sending server is set correctly, you can even leave that off, and r.http will figure out the correct type.)

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