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Library Simplified

Build Status

The NYPL's Library Simplified Android client.


Image by Predrag Kezic from Pixabay

Build Status
Nightly, DRM, JDK 11 Build Status
Nightly, DRM-Free, JDK 11 Build Status
Nightly, DRM-Free, JDK 15 Build Status
Last Commit Build Status

What Is This?

The contents of this repository provide the framework of an application used to build, amongst others, the NYPL's official SimplyE application. The framework provides a base application with numerous configuration switches, and configurable branding. The expectation is that third parties will produce final builds of applications by defining application frontends that specify dependencies on the framework, custom color schemes, and logos.

The repository contains a number of applications that are all built from the same core:

Application Module Description
Vanilla simplified-app-vanilla DRM-free generic reading application
SimplyE simplified-app-simplye The NYPL's official SimplyE application
Open eBooks simplified-app-openebooks The Open eBooks application


Building The Code

The Short Version

Make sure you clone this repository with git clone --recursive. If you forgot to use --recursive, then execute:

$ git submodule init
$ git submodule update --remote --recursive

Install an Android SDK and a JDK and run:

$ ./gradlew clean ktlint assembleDebug test

This will build all of the code and run the unit tests, but only the Vanilla application will be built by default. In order to build the other applications such as SimplyE, it's necessary to obtain the correct credentials from the NYPL and enable DRM.

The Longer Version

Android SDK

Install the Android SDK and Android Studio. We don't support the use of any other IDE at the moment.


Install a reasonably modern JDK: Java 11 is the current long-term support (LTS) release of Java. We perform nightly builds using the current LTS Java release, and the current bleeding-edge Java release in order to try to detect any upcoming compatibility issues, but we don't recommend building on anything other than the current LTS JDK for everyday usage.

Any of the following JDKs should work:

The JAVA_HOME environment variable must be set correctly. You can check what it is set to in most shells with echo $JAVA_HOME. If that command does not show anything, adding the following line to $HOME/.profile and then executing source $HOME/.profile or opening a new shell should suffice:

# Replace NNN with your particular version of 11.
export JAVA_HOME=/path/to/jdk-11+NNN

You can verify that everything is set up correctly by inspecting the results of both java -version and javac -version:

$ java -version
openjdk version "11.0.8" 2020-07-14
OpenJDK Runtime Environment (build 11.0.8+10)
OpenJDK 64-Bit Server VM (build 11.0.8+10, mixed mode)

S3 Credentials

Our application can use packages that are only available from our S3 bucket. If you wish to use these packages, you need to obtain S3 credentials and then tell Gradle to use them.

S3 credentials can be obtained by emailing or by asking in the #mobile-development channel of

Once you have your credentials, the following lines must be added to $HOME/.gradle/

# Replace ACCESS_KEY and SECRET_ACCESS_KEY appropriately.
# Do NOT use quotes around either value.

APK signing

If you wish to generate a signed APK for publishing the Vanilla application, you will need to copy a keystore to release.jks and set the following values correctly in $HOME/.gradle/

# Do NOT use quotes around values.

Note that APK files are only signed if the code is built in release mode. In other words, you need to use either of these commands to produce signed APK files:

$ ./gradlew clean assembleRelease test
$ ./gradlew clean assemble test

Enabling DRM

The application contains optional support for various DRM systems, and these must be enabled explicitly in order to build SimplyE.

Firstly, make sure you have your S3 credentials correctly configured. Then, add the following property to your $HOME/.gradle/ file:


This will instruct the build system that you want to build with DRM enabled. If you were to attempt to build the code right now, you would encounter a build failure: When DRM is enabled, the build system will check that you have provided various configuration files containing secrets that the DRM systems require, and will refuse to build the app if you've failed to do this. The build system can copy in the correct secrets for you if tell it the location of directories containing those secrets. For example, assuming that you have SimplyE's secrets in /path/to/simplye/secrets and Open eBook's secrets in /path/to/openebooks/secrets, you can add the following properties to your $HOME/.gradle/ file and the build system will copy in the required secrets at build time:

Adobe DRM Support

The project currently makes calls to the NYPL's Adobe DRM API. The API is structured in a manner that means that enabling actual support for Adobe DRM simply entails adding a dependency on the NYPL's Adobe DRM implementation. This implementation is only available to DRM licensees. Please get in touch with us if you have a DRM license and want to produce a DRM-enabled build!

Findaway Audiobook DRM support

The project currently uses the NYPL's AudioBook API to provide support for playing audio books. The API is structured such that adding support for new types of audiobooks and playback engines only involves adding those modules to the classpath. By default, the application framework only specifies a dependency on the NYPL's DRM-free audiobook player module, but there is also an NYPL-developed Findaway module for Findaway licensees. Please get in touch with us if you have a Findaway license and want to produce a Findaway-enabled build.



All new features should be created on feature branches and merged to develop once completed.

Project Structure / Architecture


The project, as a whole, roughly follows an MVC architecture distributed over the application modules. The controller in the application is task-based and executes all tasks on a background thread to avoid any possibility of blocking the Android UI thread.


Newer application modules, roughly follow an MVVM architecture. The View Model in the application exposes reactive properties and executes all tasks on a background thread. The View observes those properties and updates on the Android UI thread.


The project makes various references to APIs and SPIs. API stands for application programming interface and SPI stands for service provider interface.

An API module defines a user-visible contract (or specification) for a module; it defines the data types and abstract interfaces via which the user is expected to make calls in order to make use of a module. An API module is typically paired with an implementation module that provides concrete implementations of the API interface types. A good example of this is the accounts database: The Accounts database API declares a set of data types and interfaces that describe how an accounts database should behave. The Accounts database implementation module provides an implementation of the described API. Keeping the API specification strictly separated from the implementation in this manner has a number of benefits:

  • Substitutability: When an API has a sufficiently detailed specification, it's possible to replace an implementation module with a superior implementation without having to modify code that makes calls to the API.

  • Testability: Keeping API types strictly separated from implementation types tends to lead to interfaces that are easy to mock.

  • Understandability: Users of modules can go straight to the API specifications to find out how to use them. This cuts down on the amount of archaeological work necessary to learn how to use the application's internal interfaces.

An SPI module is similar to an API in that it provides a specification, however the defined interfaces are expected to be implemented by users rather than called by users directly. An implementor of an SPI is known as a service provider.

A good example of an SPI is the Account provider source SPI; the SPI defines an interface that is expected to be implemented by account provider sources. The file-based source module is capable of delivering account provider descriptions from a bundled asset file. The registry source implementation is capable of fetching account provider descriptions from the NYPL's registry server. Neither the SPI or the implementation modules are expected to be used by application programmers directly: Instead, implementation modules are loaded using ServiceLoader by the Account provider registry, and users interact with the registry via a published registry API. This same design pattern is used by the NYPL AudioBook API to provide a common API into which new audio book players and parsers can be introduced without needing to modify application code at all.

Modules should make every attempt not to specify explicit dependencies on implementation modules. API and implementation modules should typically only depend on other API modules, leaving the choice of implementation modules to the final application assembly. In other words, a module should say "I can work with any module that provides this API" rather than "I depend on implementation M of a particular API". Following this convention allows us to replace module implementation without having to modify lots of different parts of the application; it allows us to avoid strong coupling between modules.

Most of the modularity concepts described here were pioneered by the OSGi module system and so, although the Library Simplified application is not an OSGi application, much of the design and architecture conforms to conventions followed by OSGi applications. Further reading can be found on the OSGi web site.

Build System

The build is driven by the build.gradle file in the root of the project, with the build.gradle files in each module typically only listing dependencies (the actual dependency definitions are defined in the root build.gradle file to avoid duplicating version numbers over the whole project). Metadata used to publish builds (such as Maven group IDs, version numbers, etc) is defined in the file in each module. The file in the root of the project defines default values that are overridden as necessary by each module.

Test suite

We aggregate all unit tests in the simplified-tests module. Tests should be written using the JUnit 5 library, although at the time of writing we have one test that still requires JUnit 4 due to the use of Roboelectric.


The project is heavily modularized in order to keep the separate application components as loosely coupled as possible. New features should typically be implemented as new modules.

Module Description
org.librarysimplified.accessibility Accessibility APIs and functionality
org.librarysimplified.accounts.api Accounts API
org.librarysimplified.accounts.database Accounts database implementation
org.librarysimplified.accounts.database.api Accounts database API
org.librarysimplified.accounts.json Shared JSON classes
org.librarysimplified.accounts.registry Account provider registry implementation
org.librarysimplified.accounts.registry.api Account provider registry API
org.librarysimplified.accounts.source.filebased File/asset based registry source implementation
org.librarysimplified.accounts.source.nyplregistry NYPL registry client implementation
org.librarysimplified.accounts.source.spi Account provider source SPI
org.librarysimplified.adobe.extensions Adobe DRM convenience functions Analytics API Circulation manager analytics implementation Kotlin Android Extensions
org.librarysimplified.announcements Announcements API Open eBooks Application SimplyE Application Vanilla application
org.librarysimplified.books.api Book types Audio book support code
org.librarysimplified.books.borrowing Book borrowing
org.librarysimplified.books.bundled.api Bundled books API
org.librarysimplified.books.controller Books/Profiles controller implementation
org.librarysimplified.books.controller.api Books controller API
org.librarysimplified.books.covers Book cover loading and generation
org.librarysimplified.books.database Book database implementation
org.librarysimplified.books.database.api Book database API
org.librarysimplified.books.formats Book formats implementation
org.librarysimplified.books.formats.api Book formats API
org.librarysimplified.books.registry.api Book registry API
org.librarysimplified.boot.api Application boot API
org.librarysimplified.buildconfig.api Build-time configuration API
org.librarysimplified.cardcreator NYPL card creator
org.librarysimplified.content.api Content resolver API
org.librarysimplified.crashlytics Crashlytics
org.librarysimplified.crashlytics.api Crashlytics functionality
org.librarysimplified.documents Documents
org.librarysimplified.feeds.api Feed API
org.librarysimplified.files File utilities
org.librarysimplified.futures Guava Future extensions
org.librarysimplified.json.core JSON utilities
org.librarysimplified.links Link types
org.librarysimplified.links.json Link JSON parsing
org.librarysimplified.main Main application module
org.librarysimplified.networkconnectivity Network connectivity
org.librarysimplified.networkconnectivity.api Network connectivity API
org.librarysimplified.notifications Notification service
org.librarysimplified.oauth OAuth
org.librarysimplified.opds.auth_document OPDS authentication document parser implementation
org.librarysimplified.opds.auth_document.api OPDS authentication document parser API
org.librarysimplified.opds.core OPDS feed parser
org.librarysimplified.opds2 OPDS 2.0 model definitions
org.librarysimplified.opds2.irradia OPDS 2.0 Parser (Irradia)
org.librarysimplified.opds2.parser.api OPDS 2.0 parser API
org.librarysimplified.opds2.r2 OPDS 2.0 Parser (R2)
org.librarysimplified.parser.api Parser API
org.librarysimplified.patron Patron user profile parser implementation
org.librarysimplified.patron.api Patron user profile parser API
org.librarysimplified.presentableerror.api Presentable error API
org.librarysimplified.profiles Profile database implementation
org.librarysimplified.profiles.api Profile database API
org.librarysimplified.profiles.controller.api Profile controller API
org.librarysimplified.reader.api Reader API types
org.librarysimplified.reader.bookmarks Reader bookmark service implementation
org.librarysimplified.reader.bookmarks.api Reader bookmark service API
org.librarysimplified.reports Error reporting Application services API
org.librarysimplified.taskrecorder.api Task recorder API
org.librarysimplified.tenprint 10PRINT implementation
org.librarysimplified.tests Test suite
org.librarysimplified.tests.sandbox Sandbox for informal testing
org.librarysimplified.threads Thread utilities
org.librarysimplified.ui.accounts Accounts UI components
org.librarysimplified.ui.announcements Announcements UI components
org.librarysimplified.ui.branding Branding functionality
org.librarysimplified.ui.catalog Catalog components
org.librarysimplified.ui.errorpage Error details screen
org.librarysimplified.ui.images Image loader API for general image resources
org.librarysimplified.ui.listeners.api Listeners API
org.librarysimplified.ui.tabs Tabbed UI
org.librarysimplified.ui.onboarding Onboarding
org.librarysimplified.ui.profiles Profiles UI
org.librarysimplified.ui.screen Screen API
org.librarysimplified.ui.settings Settings screens
org.librarysimplified.ui.splash Splash screen
org.librarysimplified.ui.thread.api UI thread service
org.librarysimplified.viewer.api Viewer API
org.librarysimplified.viewer.audiobook AudioBook viewer
org.librarysimplified.viewer.epub.readium2 Readium 2 EPUB reader
org.librarysimplified.viewer.pdf PDF reader
org.librarysimplified.viewer.spi Viewer SPI
org.librarysimplified.webview WebView utilities

The above table is generated with


The codebase uses ktlint to enforce a consistent code style. It's possible to ensure that any changes you've made to the code continue to pass ktlint checks by running:

$ ./gradlew ktlint

To auto-format code style shortcomings with ktlint, run:

$ ./gradlew ktlintFormat

Release Process

Please see for documentation on our release process.


Copyright 2015 The New York Public Library, Astor, Lenox, and Tilden Foundations

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, WITHOUT WARRANTIES OR
CONDITIONS OF ANY KIND, either express or implied. See the License for the
specific language governing permissions and limitations under the License.