Binary Preferences


Dec 12, 2016
Feb 7, 2018
Alexander Efremenkov (iamironz)
Alexander Efremenkov (iamironz)
Source code


Binary Preferences

Rapidly fast and lightweight re-implementation of SharedPreferences which stores each preference in files separately, performs disk operations via NIO with memory mapped byte buffers and works IPC (between processes). Written from scratch.


  • Lightweight. Zero dependency
  • Super fast (faster than most other key/value solutions)
  • Small memory footprint while serialize/deserialize data
  • Zero copy in-memory cache
  • Persists only binary data. Not XML or JSON
  • Out of box data encryption support
  • Fully backward compatible with default SharedPreferences interface
  • Store all primitives include double, char, short and byte
  • Store complex data objects backward-compatible (see Persistable class documentation)
  • IPC support (preferences change listeners and in-memory cache works between processes)
  • Handle various exception events


Add in project

Add jitpack to repositories closure. For example, you should add it to root of build.gradle:

allprojects {
  repositories {
    maven { url "" }

Add dependency:

dependencies {
   compile "com.github.iamironz:binaryprefs:$version"

Minimal working configuration

Preferences preferences = new BinaryPreferencesBuilder(context)

Please, use only one instance of preferences by name, it saves you from non-reasoned allocations. You can store one preferences instance in application class, factory or even better just use one instance from IoC like Dagger or use another DI framework.

All parameters optional and chain-buildable.

Custom preferences name

Builder contains method which is defines desirable preferences name:

Preferences preferences = new BinaryPreferencesBuilder(context)

Default is "default" name.


You can define your own key/value vice versa encryption or use default:

Preferences preferences = new BinaryPreferencesBuilder(context)
                .keyEncryption(new XorKeyEncryptionImpl("16 bytes secret key".getBytes())))
                .valueEncryption(new AesValueEncryptionImpl("16 bytes secret key".getBytes(), "16 bytes initial vector".getBytes()))

Default is no-op encryption for key and value.

Exception handler

You can listen exceptions which throws during disk IO, serialization, task execution operations:

Preferences preferences = new BinaryPreferencesBuilder(context)
                .exceptionHandler(new ExceptionHandler() {
                    public void handle(Exception e) {
                        //perform analytics report

Default is print handler which performs e.printStacktrace() when exception event comes.

Custom save directory

You can save preferences into an custom directory:

Preferences preferences = new BinaryPreferencesBuilder(context)

Be careful: writing into external directory required appropriate runtime and manifest permissions.

IPC mode

If your app architecture is process based (services works in separate processes) and you would like to get preferences updates with consistent cache state you can enable this feature:

Preferences preferences = new BinaryPreferencesBuilder(context)

Please, note that one key change delta should be less than 1 (one) megabyte because IPC data transferring is limited by this capacity. Details here: Documentation

Dealing with Persistable

Persistable contract been added for fast and flexible saving and it's restoring complex objects. It's pretty similar like standard java Externalizable but without few methods which don't need for. For usage you just need to implement this interface with methods in your data-model.

All top level Persistable data-objects should be registered by key for understanding de/serialization contract during cache initialization.

How to register Persistable

Preferences preferences = new BinaryPreferencesBuilder(context)
                .registerPersistable(TestUser.KEY, TestUser.class)
                .registerPersistable(TestOrder.KEY, TestOrder.class)

Note about deepClone method: you should implement full object hierarchy copying for fast immutable in-memory data fetching. Main proposes for this method is local object mutability instead in-memory cache mutability.

But if your data class immutable and you define all values from constructor you just can return this from method.

Sample for explanation:

P.S.: If you have group of preferences which always stores under one transaction and you want to reduce disk IO just use Persistable for storing this bulk as close as possible.

Migration from another implementations

Builder have simple api for existing preferences migration:

Preferences preferences = new BinaryPreferencesBuilder(context)

You can append one or more preferences for migration and all will be merged into this one implementation. After successful migration all data in migrated preferences will be removed. Please note that all existing values in this implementation will be rewritten to values which migrates into. Also type information will be rewritten and lost too without any exception. If this method will be called multiple times for two or more different instances of preferences which has keys collision then last preferences values will be applied.

Logcat preferences dump

You can dump your preferences with adb console command right in logcat:

adb shell am broadcast -a com.ironz.binaryprefs.ACTION_DUMP_PREFERENCE --es "pref_name" "your_pref_name" (optional: --es "pref_key" "your_pref_key")


your_pref_name - is your preferences name which is defined in register method. your_pref_key - is your preference key, this is optional value.

How to register preferences by name:

DumpReceiver.register(name, preferences);

Fully working example of all values dump:

adb shell am broadcast -a com.ironz.binaryprefs.ACTION_DUMP_PREFERENCE --es "pref_name" "user_data"

Example only for user_id key dump:

adb shell am broadcast -a com.ironz.binaryprefs.ACTION_DUMP_PREFERENCE --es "pref_name" "user_data" --es "pref_key" "user_id"

Please note that if you create multiple instances of one preferences (e.g. in Activity#onCreate) you should unregister dump (e.g. in Activity#onDestroy) like this:



  1. Disk I/O encrypt. completed
  2. IPC completed
  3. Externalizable. completed as Persistable
  4. Preferences tooling (key set reading). completed: adb shell am broadcast -a com.ironz.binaryprefs.ACTION_DUMP_PREFERENCE --es "pref_name" "your_pref_name" (optional: --es "pref_key" "your_pref_key")
  5. Custom serializers. completed
  6. Synchronous commits. completed
  7. Store all primitives (like byte, short, char, double). completed
  8. Lock free (avoid locks). completed as LockFactory.
  9. Exact background tasks for each serialization strategies. completed
  10. Reduce events (implement events transaction). completed.
  11. Simplify api (instance creating, exception handles). completed
  12. File name encrypt completed
  13. Finalize serialization and persistence contract completed
  14. Default preferences migration mechanism complete
  15. In-memory cache initialization strategies
  16. byte[] support
  17. IPC transactions without 1mb limit
  18. Limiting strategies (UNLIMITED, LRU, FIFO)
  19. RxJava support
  20. sun.misc.Unsafe serialization mode for api 21+


Copyright 2017 Alexander Efremenkov

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   See the License for the specific language governing permissions and
   limitations under the License.