RoomAsset with selective Migration!

Thanks to MikeT https://stackoverflow.com/a/59637092/3123142

An Android helper class to manage database creation and version management using an application's raw asset files.

This library provides developers with a simple way to ship their Android app with an existing SQLite database (which may be pre-populated with data) and to manage its initial creation and any upgrades required with subsequent version releases.

It is implemented as an extension to Room, providing an easy way to use Room with an existing SQLite database.

---

Gradle Dependency

Dependency

Add this to your module's build.gradle file (make sure the version matches the last release):

Add it in your root build.gradle at the end of repositories:

allprojects {
	repositories {
		...
		maven { url "https://jitpack.io" }
	}
}

Add the dependency

dependencies {
    // ... other dependencies
    implementation 'com.github.ueen:RoomAssetHelper:1.2'
}

Basic Usage

RoomAsset is intended as a drop in alternative for the framework's Room.

You can use RoomAsset as you use Room but with two changes:

1. Use RoomAssetHelper.databaseBuilder() instead of Room.databaseBuilder()
2. Also specify the version as last parameter in the databaseBuilder
3. (optional) Specify a path under "assets" like databases/"
4. (optional) Specify the Table and columns you want to preserve

  val db = RoomAssetHelper.databaseBuilder(applicationContext, 
  					   AppDatabase::class.java,
					   "chinook.db",
					   1)
	   			.build()

RoomAsset relies upon asset file and folder naming conventions. Your assets folder will either be under your project root, or under src/main if you are using the default gradle project structure. At minimum, you must provide the following:

• A SQLite database inside the assets folder whose file name matches the database name you provide in code (including the file extension, if any)

For the example above, the project would contain the following:

assets/chinook.db

If your database is in a subfolder of assets you need to add the path relative to the assets folder in the databaseBuilder this might look like this

  val db = RoomAssetHelper.databaseBuilder(applicationContext,
  					   AppDatabase::class.java,
					   "chinook.db",
					   databasePath = "databases/",
					   1)
				.build()

Selective Migration

To preserve certain columns in your Database on the device (eg user data) you can add them in the databaseBuilder according to this schema

TablePreserve
	table: String 			//name of the table in which columns should be preserved
	preserveColumns: Array<String>, //name(s) of the columns which should be preserved on the device
    	matchByColumns: Array<String>	//unique identifier(s) (typically a `id` column) to match the rows

Important note: The original, as well as the new database must contain the columns you want to preserve and match by!

So in the end it might look something like this

  val db = RoomAssetHelper.databaseBuilder(applicationContext,
  					   AppDatabase::class.java, 
					   "chinook.db",
					   1,
					   preserve = arrayOf(TablePreserve(table = "yourTable",
					   				    preserveColumns = arrayOf("yourColumn"),
									    matchByColumns = arrayOf("id"))))
				.build()

Upgrade Database

If you want to upgrade the database, overwrite the old Database in the assets and increase the version number of the Database AND in the databaseBuilder, like this

  val db = RoomAssetHelper.databaseBuilder(applicationContext,
  					   AppDatabase::class.java, 
					   "chinook.db", 
					   version = 2)
				.build()

Supported data types: TEXT, INTEGER, REAL, BLOB

Thanks to humazed and his original RoomAsset library that this library was based on and inspired by. https://github.com/humazed/RoomAsset

License

Copyright (C) 2020 ueen

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

   http://www.apache.org/licenses/LICENSE-2.0

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.