It contains a Custom DataStoreSource that provides the ability to store custom entities types without the requirement of using Protocol Buffers.
Jetpack DataStore provides two implementations, one that stores key-value primitives types and another to stores typed objects with protocol buffers. This library provides a DataStore implementation that enables storing typed objects, just providing a DataStoreEntitySerializer.
The DataStoreEntitySerializer is an interface with two methods, one to serialize an entity from a string and the other to serialize the entity into a string.
interface DataStoreEntitySerializer {
@WorkerThread
fun <T> toString(t: T, aClass: Class<T>): String
@WorkerThread
fun <T> fromString(value: String?, aClass: Class<T>): T?
}You can choose what serializer do you prefer, for example, if you are using Gson you could define a GsonSerializer like this:
class GsonDataStoreEntitySerializer(private val gson: Gson = Gson()) : DataStoreEntitySerializer {
override fun <T> toString(t: T, aClass: Class<T>): String = gson.toJson(t)
override fun <T> fromString(value: String?, aClass: Class<T>): T? = gson.fromJson(value, aClass)After you have created the serializer, you can use the DataStoreSource. To create a DataStoreSource, you need to provide a Jetpack DataStore, a DataStoreEntitySerializer and a [CoroutineDispatcher ] to specify where you want to run the background tasks.
private val dataStoreSource = DataStoreSource(
dataStore = context.createDataStore(name = "my-data-store"),
serializer = GsonDataStoreEntitySerializer()
)The DataStoreSource provides three methods to manage the data:
inline fun <reified T> getEntity(key: String): Flow<T?> = getEntity(key, T::class.java)
suspend inline fun <reified T> putEntity(key: String, t: T) = putEntity(key, t, T::class.java)
suspend inline fun <reified T> removeEntity(key: String) = removeEntity(key, T::class.java)
After that you can create a storage to use the DataStoreSource. In the sample app, it's defined a SessionRepository which manages the app's session information.
private const val DATA_STORE_NAME = "data_store_name"
private val Context.appSessionDataStore: DataStore<Preferences> by preferencesDataStore(name = DATA_STORE_NAME)
class SessionRepository(context: Context) {
companion object {
private const val SESSION_REPOSITORY_KEY = "session"
}
private val dataStore = DataStoreSource(
context.appSessionDataStore(),
GsonDataStoreEntitySerializer()
)
val session: Flow<Session?>
get() = dataStore.getEntity(SESSION_REPOSITORY_KEY)
suspend fun saveSession(session: Session?) =
dataStore.putEntity(SESSION_REPOSITORY_KEY, session)
}