I'm facing an issue, like if my repository injected was not a Singleton.
I have a repository (in reality many, but let's make it simple) marked as #Singleton
#Module
#InstallIn(SingletonComponent::class)
class AppModule {
#Provides
#Singleton
fun provideSettingsRepository(#ApplicationContext context: Context): SettingsRepository {
return SettingsRepositoryImpl(context)
}
}
Here the implementation of my repository :
class SettingsRepositoryImpl(context: Context) : SettingsRepository {
private var _flow = MutableStateFlow("init value")
override fun getFlow(): StateFlow<String?> = _flow.asStateFlow()
override fun setMyValue(value:String) {
_flow.value = value
}
}
When I use it apart of my service (in some viewModels or others class with DI), it work perfectly. Today I implemented an AIDL service and wanted to do some DI. I had to use field injection because the service constructor has to be empty. It seems like the update made from my application isen't reported on my "TestApplication" who consume the Service (like if I had two instance of my repository).
Here the code of my service :
#AndroidEntryPoint
class AppService : Service() {
#Inject lateinit var settingsRepository: SettingsRepository
fun someActionOnMyRepository() {
settingsRepository.setMyValue("whatever")
}
}
When I set the value from my UI (viewModel or any other class who as the repository injected), it's not updated in my service. The flow doesn't contains the new value (tested by debug or logcat).
I'm expecting my settingsRepository to be a singleton. What am I missing ? Is it because the field injection ?
Best regards
Ok, the problem was not from Hilt but about how i declared my service in my AndroidManisfest.xml
<service android:name=".services.MyAppService"
android:process=":remote" <----- THIS
android:exported="true">
Making it like that make it on another process. That mean it's like another app instance (so no more Singleton / SharedPreferences).
Related
I have a test class that looks something like this
Behind the scenes, we're using Guice and DropwizardAwareModule to configure the binding and provide instantiated classes/beans.
class SomeTest {
companion object {
#RegisterExtension
#JvmField
val app = TestGuiceyAppExtension.forApp(MyServer::class.java)
.config(configFileName).hooks(GuiceyConfigurationHook {
builder(it)
}).create()
}
#Inject
#Named("something")
private lateinit var someClass: SomeClass
}
The SomeClass is defined in the following way:
class SomeClass(firstClass: FirstClass, secondClass: SecondClass) {
}
With no constructor injection.
In a separate DropwizardAwareModule, I define a Provides function that provides 2 possible instances of SomeClass. For example -
#Provides
#Named("something")
fun getSomeClass(firstClass: FirstClass, secondClass: SecondClass) {
return SomeClass(firstClass, secondClass)
}
The test class fails to inject SomeClass, claiming it doesn't have a no-args constructor, nor an #Inject annotated constructor, fair enough.
However, if I transform the field injection into a constructor injection, it works flawlessly.
That is - this configuration works well, and the SomeClass instance I provided in the module above, shows up alright.
class SomeTest #Inject constructor(#Named("something") someClass: SomeClass) {
}
Why is it so? is it because of some limitation in test classes? or is it something to do with #Provides generating an immutable instance, whereas field injection requires mutable objects?
Thanks!
I've recently started to learn Dagger. In order to do that, i've decided to write a simple console application to get the feeling of how various dagger features (like modules, component, subcomponents and component dependencies) fit together in an app architecture. As I don't really understeand it and given how hard it is to find an application sample created with dagger2 which is not Android app, i've decided to open a question here.
The first and probably most important question is: is dagger2 even ment to be used outside android?
If yes, then lets consider a simple application architecture: we have the data layer, service layer and ui layer
Data layer might consist of some kind of facade:
(Following code snippets will be written in Kotlin)
class Entity(var id: Int)
interface Repository {
fun findEntityById(id: Int): Entity?
fun deleteEntity(entity: Entity): Boolean
fun saveEntity(entity: Entity): Boolean
fun findAllEntities(): List<Entity>
}
Then i could have a couple of implementations of this facade:
class InMemoryRepository #Inject constructor() : Repository {
private val entities: MutableList<Entity> = LinkedList()
override fun findEntityById(id: Int): Entity? = entities.firstOrNull { it.id == id }
override fun deleteEntity(entity: Entity) = entities.remove(entity)
override fun saveEntity(entity: Entity) = entities.add(entity)
override fun findAllEntities(): List<Entity> = LinkedList(entities)
}
For which i would have modules:
#Module
interface InMemoryPersistenceModule {
#Singleton
#Binds
fun bindRepository(rep: InMemoryRepository): Repository
}
Service layer would be simpler:
#Singleton
class Service #Inject constructor(repository: Repository) {
fun doSomeStuffToEntity(entity: Entity) {}
}
#Singleton
class AnotherService #Inject constructor(repository: Repository) {
fun doSomeStuffToEntity(entity: Entity) {}
}
But it gets a little bit unlcear when it comes to the UI layer. Lets say i have some kind of android-like activity:
interface Activity : Runnable
And some kind of class that manages those activities:
class UserInterfaceManager {
val activityStack: Stack<Activity> = Stack()
val eventQueue: Queue<Runnable> = LinkedList()
fun startActivity(activity: Activity) = postRunnable {
activityStack.push(activity)
activity.run()
}
fun postRunnable(callback: () -> Unit) = eventQueue.add(callback)
fun stopActivity() { TODO() }
//other
}
How does dagger fit into this scenario? The articles i have read about the the dagger with android suggest createing the application component to inject my activites:
#Singleton
#Component(modules = [InMemoryPersistenceModule::class])
interface ApplicationComponent {
fun injectSomeActivity(activity: SomeActivity)
// and more
}
But then, where would the injection go to? It does't really make sense to put it in the UserInterfaceManager as Activities will most likely need an instance of it, which would create a circular dependency.
I also do not like the idea of the component being obtained from some kind of static method/property and injecting the activity from inside of it at the startup, as it creates duplicate lines of code in each activity.
Also, where do components and subcomponents fit in this kind of architecture? Why not create the separate
component for the data layer and expose just the repository and declare it as a dependency of the app component which would further isolate the details from abstraction? Maybe i should declare this component a dependcy of a service component which would enforce the layer architecure, as components can only use the types exposed in component interface? Or maybe i should use compoenent only when i need a custom scope and use the modules everywhere elsewhere?
I just overally think I am missing the bigger picture of the dagger. I will be really greatefull for answers, explanations and links to articles and other resouces that will let me understeand it better.
From the perspective of an Android developer, I fully understand your point. I asked myself this question too. The way how you construct an object in plain Java/Kotlin world is a little bit different. The main reason is due to the fact basic Android components (Activity/Fragment) don't allow constructor injection.
The answer to your question is, though, pretty straightforward. The Dagger Component is responsible for object creation, and you, as a developer, control what objects specific component provides. Let's use it in your scenario and provide some of the objects you might be interested in:
#Singleton
#Component(modules = [InMemoryPersistenceModule::class])
interface ApplicationComponent {
val service: Service
val anotherService: AnotherService
}
ApplicationComponent should be understood as a component for your whole application. It's not related to Android's Application class in any way. Now, you can simply create your component and let Dagger instantiate your objects:
val component = DaggerApplicationComponent.create()
val anotherService: AnotherService = component.anotherService
val service: AnotherService = component.service
In Kotlin, a common use for object is using it for singletons, like:
object MyObject {
...
}
However, when using micronaut framework, the official documentation recommends using something like this:
#Singleton
class V8Engine : Engine {
override var cylinders = 8
override fun start(): String {
return "Starting V8"
}
}
Why can't I use simply object instead of using annotation #Singleton with a class?
With a #Singleton, Micronaut can automatically manage dependencies between beans. If you go with the other class in https://docs.micronaut.io/latest/guide/ioc.html#beans, translated to Kotlin:
#Singleton
class Vehicle(private val engine: Engine) {
public fun start() = engine.start()
}
It can't be just an object because takes a parameter.
This parameter is discovered by Micronaut to be the singleton instance of V8Engine, which needs that to be a #Singleton and not an object.
Of course, in this case you could just directly use V8Engine in Vehicle; but it's easier to change e.g. if you want Engine not to be a singleton anymore.
Why can't I use simply object instead of using annotation #Singleton
with a class?
You can use object instead of using #Singleton with a class. Micronaut won't manage instances for you, but that is allowed.
I am trying to use Neo4j TestContainers with Kotlin, Spring Data Neo4j, Spring Boot and JUnit 5. I have a lot of tests that require to use the test container. Ideally, I would like to avoid copying the container definition and configuration in each test class.
Currently I have something like:
#Testcontainers
#DataNeo4jTest
#Import(Neo4jConfiguration::class, Neo4jTestConfiguration::class)
class ContainerTest(#Autowired private val repository: XYZRepository) {
companion object {
const val IMAGE_NAME = "neo4j"
const val TAG_NAME = "3.5.5"
#Container
#JvmStatic
val databaseServer: KtNeo4jContainer = KtNeo4jContainer("$IMAGE_NAME:$TAG_NAME")
.withoutAuthentication()
}
#TestConfiguration
internal class Config {
#Bean
fun configuration(): Configuration = Configuration.Builder()
.uri(databaseServer.getBoltUrl())
.build()
}
#Test
#DisplayName("Create xyz")
fun testCreateXYZ() {
// ...
}
}
class KtNeo4jContainer(val imageName: String) : Neo4jContainer<KtNeo4jContainer>(imageName)
How can I extract the databaseServer definition and the #TestConfiguration? I tried different ways of creating a base class and having the ContainerTest extend it, but it is not working. From what I understand, static attriubutes are not inherited in Kotlin.
Below my solution for sharing same container between tests.
#Testcontainers
#SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
abstract class IntegrationTest {
companion object {
#JvmStatic
private val mongoDBContainer = MongoDBContainer(DockerImageName.parse("mongo:4.0.10"))
.waitingFor(HostPortWaitStrategy())
#BeforeAll
#JvmStatic
fun beforeAll() {
mongoDBContainer.start()
}
#JvmStatic
#DynamicPropertySource
fun registerDynamicProperties(registry: DynamicPropertyRegistry) {
registry.add("spring.data.mongodb.host", mongoDBContainer::getHost)
registry.add("spring.data.mongodb.port", mongoDBContainer::getFirstMappedPort)
}
}
}
The key here is to not use #Container annotation as it will close just created container after your first test subclass executes all tests.
Method start() in beforeAll() initialize container only once (upon first subclass test execution), then does nothing while container is running.
By theory we shouldn't have to do this hack, based on:
https://www.testcontainers.org/test_framework_integration/junit_5/
...container that is static should not be closed until all of tests of all subclasses are finished, but it's not working that way and I don't know why. Would be nice to have some answer on that :).
I've had the same issue (making Spring Boot + Kotlin + Testcontainers work together) and after searching the web for (quite) a while I found this nice solution: https://github.com/larmic/testcontainers-junit5. You'll just have to adopt it to your database.
I faced very similar issue in Kotlin and spring boot 2.4.0.
The way you can reuse one testcontainer configuration can be achieved through initializers, e.g.:
https://dev.to/silaev/the-testcontainers-mongodb-module-and-spring-data-mongodb-in-action-53ng or https://nirajsonawane.github.io/2019/12/25/Testcontainers-With-Spring-Boot-For-Integration-Testing/ (java versions)
I wanted to use also new approach of having dynamicProperties and it worked out of a boxed in java. In Kotlin I made sth like this (I wasn't able to make #Testcontainer annotations working for some reason). It's not very elegant but pretty simple solution that worked for me:
MongoContainerConfig class:
import org.testcontainers.containers.MongoDBContainer
class MongoContainerConfig {
companion object {
#JvmStatic
val mongoDBContainer = MongoDBContainer("mongo:4.4.2")
}
init {
mongoDBContainer.start()
}
}
Test class:
#SpringBootTest(
classes = [MongoContainerConfig::class]
)
internal class SomeTest {
companion object {
#JvmStatic
#DynamicPropertySource
fun setProperties(registry: DynamicPropertyRegistry) {
registry.add("mongodb.uri") {
MongoContainerConfig.mongoDBContainer.replicaSetUrl
}
}
}
Disadvantage is this block with properties in every test class what suggests that maybe approach with initializers is desired here.
I'm using Dagge2 in my kotlin project with pom file. I worked with Dagger in my android projects and it worked fine. But somehow I don't understand why Dagger generating multiple instances of my every object in kotlin.
Below is my Component
#Singleton
#Component(modules = [MeterCollectionModule::class])
interface AppComponent {
fun meterCollection(): MeterCollection
}
And this is my Module
#Module(includes = [UtilModule::class])
class MeterCollectionModule {
#Singleton
#Provides
fun meterCollection() = MeterCollection()
}
That's how I'm building my AppComponent
DaggerAppComponent
.builder()
.build()
.inject(this)
I debug my code and see, every time I inject MeterCollection class it gives me new object.
The #Singleton annotation (as well as any other scope annotation) is taken into account only if you're reusing the same component. In other words, Dagger is not able to respect your #Singleton scope across different instances of the same component.
Hence, in order to inject the same MeterCollection instance, you should also reuse the same DaggerAppComponent instance (e.g., by putting it in an instance variable).
Singleton and Provider annotations won't work with object which is created every time method is called. I'd refactor the class to:
#Module(includes = [UtilModule::class])
class MeterCollectionModule {
val myMeterConnection = MeterConnection()
#Singleton
#Provides
fun meterCollection(){
return myMeterConnection
}
(which is identical solution to what #user2340612 proposed)