ObjectStore

A modular object storage framework for Kotlin multiplatform projects.

Usage

ObjectStore provides a simple key/value storage interface which by default uses Type details to derive the Key automatically. To create an ObjectStore you need two things:

• ObjectStoreWriter: Providers the persistence mechanism to store data for later access.
• ObjectStoreSerializer: Provides the serialization mechanism to transform objects for storage.

val store = ObjectStore(
    storeWriter = SharedPreferencesStoreWriter("prefs", context),
    storeSerializer = JsonStoreSerializer()
)

// Store an object
store.put(User("username", "email", ...))

// Get an object or null
val user: User? = store.getOrNull<User>()
// Get an object or throw
val user: User = store.get<User>()
// Get an object or default
val user: User = store.get(default = User(...))

// Get a StateFlow
val userFlow: StateFlow<User?> = store.getFlow<User>()
// Calls to `put` new user objects will be emitted
userFlow.collect { println(it) }

// Get all keys
store.keys()

// Remove an object
store.remove<User>()
// Remove all objects
store.clear()

When storing basic types such as String, Boolean, etc. you must provide a key for the record.

store.put(false, key = "my_key")
store.get<Boolean>(default = false, key = "my_key")

NOTE: When targeting Javascript, all classes used with ObjectStore must be annotated with @Serializable. This is used to derive class and parameter name based keys, other platforms do not use the Kotlinx.serialization library in objectstore-core.

Serializers

Turning objects into data suitable for storage requires a ObjectStoreSerializer implementation. The following modules provide serialization capabilities using the matching Kotlinx.serialization module.

• objectstore-cbor: CborStoreSerializer()
• objectstore-json: JsonStoreSerializer()
• objectstore-protobuf: ProtoBufStoreSerializer()

Writers

Storing object data requires a ObjectStoreWriter implementation. The following Writers are provided in the objectstore-core module:

• Android: SharedPreferencesStoreWriter("prefs_name", context)
• iOS/macOS/tvOS/watchOS: UserDefaultsStoreWriter()
• Browser JS: LocalStorageStoreWriter()
• All: InMemoryStoreWriter()

File Writer

The objectstore-fs provides file based storage using okio. All targets are supported except iosArm32 and jsBrowser.

val store = ObjectStore(
    storeWriter = FileStoreWriter("/storage-directory")
)

The provided path must not exist or be an existing directory where files can be stored. Each value will be stored in a separate file using the hex encoded key as the filename.

Secure Writers

To store data in a secure way, the objectstore-secure module provides Writers which encrypt data when stored on disk.

• iOS/macOS/tvOS/watchOS: KeychainStoreWritre("com.service.name", "com.service.group")
• Android: EncryptedSharedPreferencesStoreWriter("prefs_name", context)

Wrapped Writers

The ValueTransformingStoreWriter provides a hook to encode/decode values before they are written to disk. The transform methods are defined as (type: KType, value: T) -> T, when unhandled you must return the original value.

val storeWriter = InMemoryStoreWriter().transformValue(
    transformGet = { _, value -> (value as? String)?.base64Decoded() ?: value },
    transformSet = { _, value -> (value as? String)?.base64Encoded() ?: value }
)

The MemCachedStoreWriter provides lazy in-memory caching around any ObjectStoreWriter implementation.

val storeWriter = FileStoreWriter("/data").memCached()

Download

repositories {
    mavenCentral()
    // Or snapshots
    maven("https://s01.oss.sonatype.org/content/repositories/snapshots/")
}

dependencies {
    implementation("org.drewcarlson:objectstore-core:$VERSION")
    
    // Serializers
    implementation("org.drewcarlson:objectstore-cbor:$VERSION")
    implementation("org.drewcarlson:objectstore-json:$VERSION")
    implementation("org.drewcarlson:objectstore-protobuf:$VERSION")
    
    // Writers
    implementation("org.drewcarlson:objectstore-fs:$VERSION")
    implementation("org.drewcarlson:objectstore-secure:$VERSION")
}

[versions]
objectstore = "1.0.0-SNAPSHOT"

[libraries]
objectstore-core = { module = "org.drewcarlson:objectstore-core", version.ref = "objectstore" }
objectstore-fs = { module = "org.drewcarlson:objectstore-fs", version.ref = "objectstore" }
objectstore-cbor = { module = "org.drewcarlson:objectstore-cbor", version.ref = "objectstore" }
objectstore-json = { module = "org.drewcarlson:objectstore-json", version.ref = "objectstore" }
objectstore-protobuf = { module = "org.drewcarlson:objectstore-protobuf", version.ref = "objectstore" }
objectstore-secure = { module = "org.drewcarlson:objectstore-secure", version.ref = "objectstore" }

License

This project is licensed under Apache-2.0, found in LICENSE.