I am trying to understand codelab 6.2 Coroutines and Room in Android Kotlin Fundamentals. Class SleepTrackerViewModel includes (with comments added by me):
private var tonight = MutableLiveData<SleepNight?>()
private suspend fun getTonightFromDatabase(): SleepNight? {
var night = database.getTonight() // this gets the most recent night
// Return null if this night has been completed (its end time has been set).
if (night?.endTimeMilli != night?.startTimeMilli) {
night = null
}
return night
}
fun onStartTracking() {
viewModelScope.launch {
val newNight = SleepNight()
insert(newNight)
tonight.value = getTonightFromDatabase()
}
}
fun onStopTracking() {
viewModelScope.launch {
val oldNight = tonight.value ?: return#launch
oldNight.endTimeMilli = System.currentTimeMillis()
update(oldNight)
}
}
I don't understand why the method getTonightFromDatabase(), which is called only from onStartTracking(), is needed. It seems the last statement in onStartTracking() could be replaced by:
tonight.value = newNight
I also don't understand why the conditional in getTonightFromDatabase() is needed.
One of the reasons is that the nightId in the SleepNight data class is auto generated by SQL.
If the code would do tonight.value = newNight then the nightId wouldn't be the same than the one in the database. That would cause the update call in onStopTracking to end (update) the wrong night.
Note too that the method getTonightFromDatabase is called from a later version of SleepNightViewModel:
private var tonight = MutableLiveData<SleepNight?>()
init {
initializeTonight()
}
private fun initializeTonight() {
viewModelScope.launch {
tonight.value = getTonightFromDatabase()
}
}
When the application restarts, getTonightFromDatabase is called to set the instance variable tonight (which would more accurately be called latestNight). If the most recent night was complete, the completeness check would ensure that null is returned, prevent the entry from being modified.
Related
My requirement is to display the notes in pages using clean architecture along with offline suppport.
I am using the Paging library for pagination. And below is the clean architectural diagram for getting notes.
Note: Please open the above image in new tab and zoom to view it clear.
I have four layers UI, UseCase, Repository, and Datasource. I am planning to abstract the internal implementation of the data source. For that, I need to map NotesEntities to another model before crossing the boundary.
class TimelineDao{
#Transaction
#Query("SELECT * FROM NotesEntities ORDER BY timeStamp DESC")
abstract fun getPagingSourceForNotes(): PagingSource<Int, NotesEntities>
}
Current Implementation:
internal class NotesLocalDataSourceImpl #Inject constructor(
private val notesDao: NotesDao
) : NotesLocalDataSource {
override suspend fun insertNotes(notes: NotesEntities) {
notesDao.insert(NotesEntities)
}
override fun getNotesPagingSource(): PagingSource<Int, NotesEntities> {
return notesDao.getPagingSourceForNotes()
}
}
Expected Implementation:
internal class NotesLocalDataSourceImpl #Inject constructor(
private val notesDao: NotesDao
) : NotesLocalDataSource {
override suspend fun insertNotes(notes: NotesRepositoryModel) {
notesDao.insert(NotesRepositoryModel.toEntity())
}
override fun getNotesPagingSource(): PagingSource<Int, NotesRepositoryModel> {
return notesDao.getPagingSourceForNotes().map{ it.toNotesRepositoryModel() }
}
}
I am having an issue mapping the PagingSource<Int, NotesEntities> to PagingSource<Int, NotesRespositoryModel>. As for as I have researched, there is no way to map
PagingSource<Int, NotesEntities> to PagingSource<Int, NotesRespositoryModel>
Kindly let me know if there is a clean way/ workaround way to map the paging source objects. If anyone is sure if there is no way as of now. Please leave a comment as well.
Please Note: I am aware that paging allows transformation for PagingData. Below is code snippet that gets notes in pages. It maps NotesEntities to NotesDomainModel. But then I want to use NotesRespositoryModel instead of NotesEntities in the NotesRespositoryImpl, abstracting the NotesEntities within NotesLocalDataSourceImpl layer.
override fun getPaginatedNotes(): Flow<PagingData<NotesDomainModel>> {
return Pager<Int, NotesEntities>(
config = PagingConfig(pageSize = 10),
remoteMediator = NotesRemoteMediator(localDataSource,remoteDataSource),
pagingSourceFactory = localDataSource.getNotesPagingSource()
).flow.map{ it.toDomainModel() }
}
The solution I have thought of:
Instead of using the PagingSource in Dao directly, I thought of creating a custom PagingSource, that calls the Dao and maps the NoteEntities to LocalRepositoryModel.
But then I need to understand that any updates to the DB will not be reflected in the PagingSource. I need to handle it internally.
Kindly let me know your thoughts on this.
What about creating an implementation of PagingSource that forwards all of the calls to the original PagingSource and performs the mapping, something like this:
class MappingPagingSource<Key: Any, Value: Any, MappedValue: Any>(
private val originalSource: PagingSource<Key, Value>,
private val mapper: (Value) -> MappedValue,
) : PagingSource<Key, MappedValue>() {
override fun getRefreshKey(state: PagingState<Key, MappedValue>): Key? {
return originalSource.getRefreshKey(
PagingState(
pages = emptyList(),
leadingPlaceholderCount = 0,
anchorPosition = state.anchorPosition,
config = state.config,
)
)
}
override suspend fun load(params: LoadParams<Key>): LoadResult<Key, MappedValue> {
val originalResult = originalSource.load(params)
return when (originalResult) {
is LoadResult.Error -> LoadResult.Error(originalResult.throwable)
is LoadResult.Invalid -> LoadResult.Invalid()
is LoadResult.Page -> LoadResult.Page(
data = originalResult.data.map(mapper),
prevKey = originalResult.prevKey,
nextKey = originalResult.nextKey,
)
}
}
override val jumpingSupported: Boolean
get() = originalSource.jumpingSupported
}
Usage would be like this then:
override fun getNotesPagingSource(): PagingSource<Int, NotesRepositoryModel> {
return MappingPagingSource(
originalSource = notesDao.getPagingSourceForNotes(),
mapper = { it.toNotesRepositoryModel() },
)
}
Regarding the empty pages in PagingState - mapping all loaded pages back to original value would be too expensive and room's paging implementation is only using anchorPosition and config.initialLoadSize anyway - see here and here.
I want to test a state stored aggregate by using AggregateTestFixture. However I get AggregateNotFoundException: No 'given' events were configured for this aggregate, nor have any events been stored. error.
I change the state of the aggregate in command handlers and apply no events since I don't want my domain entry table to grow unnecessarily.
Here is my external command handler for the aggregate;
open class AllocationCommandHandler constructor(
private val repository: Repository<Allocation>,
) {
#CommandHandler
fun on(cmd: CreateAllocation) {
this.repository.newInstance {
Allocation(
cmd.allocationId
)
}
}
#CommandHandler
fun on(cmd: CompleteAllocation) {
this.load(cmd.allocationId).invoke { it.complete() }
}
private fun load(allocationId: AllocationId): Aggregate<Allocation> =
repository.load(allocationId)
}
Here is the aggregate;
#Entity
#Aggregate
#Revision("1.0")
final class Allocation constructor() {
#AggregateIdentifier
#Id
lateinit var allocationId: AllocationId
private set
var status: AllocationStatusEnum = AllocationStatusEnum.IN_PROGRESS
private set
constructor(
allocationId: AllocationId,
) : this() {
this.allocationId = allocationId
this.status = AllocationStatusEnum.IN_PROGRESS
}
fun complete() {
if (this.status != AllocationStatusEnum.IN_PROGRESS) {
throw IllegalArgumentException("cannot complete if not in progress")
}
this.status = AllocationStatusEnum.COMPLETED
apply(
AllocationCompleted(
this.allocationId
)
)
}
}
There is no event handler for AllocationCompleted event in this aggregate, since it is listened by an other aggregate.
So here is the test code;
class AllocationTest {
private lateinit var fixture: AggregateTestFixture<Allocation>
#Before
fun setUp() {
fixture = AggregateTestFixture(Allocation::class.java).apply {
registerAnnotatedCommandHandler(AllocationCommandHandler(repository))
}
}
#Test
fun `create allocation`() {
fixture.givenNoPriorActivity()
.`when`(CreateAllocation("1")
.expectSuccessfulHandlerExecution()
.expectState {
assertTrue(it.allocationId == "1")
};
}
#Test
fun `complete allocation`() {
fixture.givenState { Allocation("1"}
.`when`(CompleteAllocation("1"))
.expectSuccessfulHandlerExecution()
.expectState {
assertTrue(it.status == AllocationStatusEnum.COMPLETED)
};
}
}
create allocation tests passes, I get the error on complete allocation test.
The givenNoPriorActivity is actually not intended to be used with State-Stored aggregates. Quite recently an adjustment has been made to the AggregateTestFixture to support this, but that will be released with Axon 4.6.0 (the current most recent version is 4.5.1).
That however does not change the fact I find it odd the complete allocation test fails. Using the givenState and expectState methods is the way to go. Maybe the Kotlin/Java combination is acting up right now; have you tried doing the same with pure Java, just for certainty?
On any note, the exception you share comes from the RecordingEventStore inside the AggregateTestFixture. It should only occur if an Event Sourcing Repository is used under the hood (by the fixture) actually since that will read events. What might be the culprit, is the usage of the givenNoPriorActivity. Please try to replace that for a givenState() providing an empty Aggregate instance.
I'm developing a app with Spring Boot 2.0 and Kotlin using the WebFlux framework.
I want to check if a user id exits before save a transaction. I'm stucked in a simple thing like validate if a Mono is empty.
fun createTransaction(serverRequest: ServerRequest) : Mono<ServerResponse> {
val transaction = serverRequest.body(BodyExtractors.toMono(Transaction::class.java))
transaction.flatMap {
val user = userRepository.findById(it.userId)
// If it's empty, return badRequest()
}
return transaction.flatMap { transactionRepository.save(it).then(created(URI.create("/transaction/" + it.id)).build()) }
}
It is possible to do what I want?
The techniques that allow checking whether Flux/Mono is empty
Using operators .switchIfEmpty/.defaultIfEmpty/Mono.repeatWhenEmpty
Using mentioned operators you will be able to react to the case when Stream has been completed without emitting any elements.
First of all, remember that operators such .map, .flatMap, .filter and many others will not be invoked at all if there no onNext has been invoked.
That means that in your case next code
transaction.flatMap {
val user = userRepository.findById(it.userId)
// If it's empty, return badRequest()
}
return transaction.flatMap { transactionRepository.save(it).then(created(URI.create("/transaction/" + it.id)).build()) }
will not be invoked at all, if transaction will be empty.
In case if there is a requirement for handling cases when your flow is empty, you should consider operators like next in the following manner:
transaction
.flatMap(it -> {
val user = userRepository.findById(it.userId)
})
.swithIfEmpty(Flux.defer(() -> Flux.just(badRequest())));
Actual solution
Also, I have noted that you created two sub-flows from the main transaction. Actually, following code will not be executed at all:
transaction.flatMap {
val user = userRepository.findById(it.userId)
// If it's empty, return badRequest()
}
and will be only executed the last one, which is returned from the method. That happens because you ain't subscribed using operator .subscribe(...).
The second point, you can't subscribe to the same request body more the one time (kind of limitation for WebClient's reponse). Thus you are required to share your request body in the next way, so completed example will be:
fun createTransaction(serverRequest: ServerRequest): Mono<ServerResponse> {
val transaction = serverRequest.body(BodyExtractors.toMono(Transaction::class.java)).cache()
transaction
.flatMap { userRepository.findById(it.userId) }
.flatMap { transaction.flatMap { transactionRepository.save(it) } }
.flatMap { ServerResponse.created(URI.create("/transaction/" + it.id)).build() }
.switchIfEmpty(transaction.flatMap { ServerResponse.badRequest().syncBody("missed User for transaction " + it.id) })
}
Or more simple case without sharing transaction flow but using Tuple:
fun createTransaction(serverRequest: ServerRequest): Mono<ServerResponse> {
val emptyUser = !User()
val transaction = serverRequest.body<Mono<Transaction>>(BodyExtractors.toMono(Transaction::class.java))
transaction
.flatMap { t ->
userRepository.findById(t.userId)
.map { Tuples.of(t, it) }
.defaultIfEmpty(Tuples.of(t, emptyUser))
}
.flatMap {
if (it.t2 != emptyUser) {
transactionRepository.save(it.t1)
.flatMap { ServerResponse.created(URI.create("/transaction/" + it.id)).build() }
} else {
ServerResponse.badRequest().syncBody("missed User for transaction " + it.t1.id)
}
}
}
You can check it using the Mono's provided method hasElement() which is analogous to Optional's isPresent(). The method definition is :
Mono<Boolean> hasElement()
for more details checkout : project reactor documentation
In case you have to perform some action based on this value you can further use switchIfEmpty() to provide with alternate publisher.
Let me start by saying I am a newbie on reactive (java) and on this forum.
I think you cannot really check in this code if a mono is empty because a mono represents code that will be executed later on, so in this code body you won't know yet if its is empty. Does that make sense?
I just wrote something similar in Java which seems to work (but not 100% this is the best approach either):
public Mono<ServerResponse> queryStore(ServerRequest request) {
Optional<String> postalCode = request.queryParam("postalCode");
Mono<ServerResponse> badQuery = ServerResponse.badRequest().build();
Mono<ServerResponse> notFound = ServerResponse.notFound().build();
if (!postalCode.isPresent()) { return badQuery; }
Flux<Store> stores = this.repository
.getNearByStores(postalCode.get(), 5);
return ServerResponse.ok().contentType(APPLICATION_JSON)
.body(stores, Store.class)
.switchIfEmpty(notFound);
}
We can use switchIfEmpty method for this
Below example, I'm checking if the user exists with email if not then add it
userRepository.findByEmail(user.getEmail())
.switchIfEmpty(s -> {
user.setStatus("InActive");
String encodedPassword = DigestUtils.sha256Hex(user.getPassword());
user.setPassword(encodedPassword);
userRepository.save(user).subscribe();
s.onComplete();
}).then(Mono.just(user));
Use Mono with Optional:
return findExistingUserMono
.map(Optional::of)
.defaultIfEmpty(Optional.empty())
.flatMap(optionalUser -> {
if(optionalUser.isPresent()) {
return Mono.error('xxxx');
}
return this.userService.create(optionalUser.get());
});
This way it will always emit Optional value so that the stream will never break.
READ EDIT
I have a similar implementation to AsyncCrudAppService related to filtering queries. When I run tests on top of ABPs implementation of Application Services derived of AsyncCrudAppServiceBase, everything runs fine. When I do the same running on top of my custom "filters", I get the following error:
System.ObjectDisposedException : Cannot access a disposed object [...]
Object name: 'DataManagerDbContext'.
I know the solution is using IUnitOfWorkManager and calling Begin() method to define a UnitOfWork, but since I am working with AppServices, I thought there was already a UnitOfWork defined. These are my methods:
public PagedResultDto<StateDetails> GetEditorList(EditorRequestDto input)
{
var query = _stateRepository.GetAllIncluding(p => p.Country).AsQueryable();
query = ApplySupervisorFilter(query);
query = query.ApplyFiltering(input, "Name");
var totalCount = query.Count();
query = query.ApplySorting<State, int, PagedAndSortedResultRequestDto>(input);
query = query.ApplyPaging<State, int, PagedAndSortedResultRequestDto>(input);
var entities = query.ToList();
return new PagedResultDto<StateDetails>(totalCount, ObjectMapper.Map<List<StateDetails>>(entities));
}
private IQueryable<State> ApplySupervisorFilter(IQueryable<State> query)
{
if (!SettingManager.GetSettingValue<bool>(AppSettingNames.SupervisorFlag))
{
query = ApplyUncategorizedFilter(query);
}
return query;
}
private IQueryable<State> ApplyUncategorizedFilter(IQueryable<State> query)
{
return query.Where(
p => !p.CountryId.HasValue);
}
My passing test (with manual UnitOfWork):
[Fact]
public async Task GetEditorListWithouSupervisorFlag_Test()
{
using (UnitOfWorkManager.Begin())
{
await ChangeSupervisorFlag(false);
var result = _stateAppService.GetEditorList(
new EditorRequestDto
{
MaxResultCount = 10,
});
result.Items.Any(p => p.Country == null).ShouldBe(true);
}
}
Does anybody know an solution to this "issue"? It would be annoying to define a UnitOfWork for every test I perform. It also seems like I am doing something wrong
EDIT
I have solved the issue. I must use an interface for my Application Service when running tests so it is able to mock it properly
I have solved the issue. I must use an interface for my Application Service when running tests so it is able to mock it properly
I am trying to perform a relatively simple task: to wait until a page redirect is complete. Just seen another answered question on the subject, where an advice is to wait for a particular text on the latter page to appear (IF I've got it right). If so, how about waiting till window.location will be changed? Is it better? Worse? Less applicable? Any other idea? just curious, if needed, can mark this question as a community wiki.
Thanks!
Yes I've encountered this problem many times when using Selenium. There are 2 ways I worked around this problem. First off you can actually change the implicit wait time. For example given this piece of code:
Actions builder = new Actions( driver );
builder.click( driver.findElement( By.className("lala") ) ).perform();
This code will throw an exception if at the point it's called there are no elements that could be found to match the "lala" class. You can change this implicit wait time with:
driver.manage().timeouts().implicitlyWait( 5, TimeUnit.SECONDS );
This makes the driver poll for 5 seconds instead of failing straight away. If the element still can't be located after 5 seconds then the action will fail. Of course you can change that setting. I found that this method works okay the majority of the time. Most of the time you don't care about the whole page loading, just a certain part.
I also wrote another function which is GetElementByClassAndText which will do the same as implicit wait on an element except it also checks the containing text as well to allow finer detailing of what you want:
public static void waitAndClick( WebDriver driver, By by, String text ) {
WebDriverWait wait = new WebDriverWait( driver, 10000 );
Function<WebDriver, Boolean> waitForElement = new waitForElement( by );
wait.until( waitForElement );
for( WebElement e : driver.findElements( by ) ) {
if( e.getText().equals( text ) ) {
Actions builder = new Actions( driver );
builder.click( e ).perform();
return;
}
}
}
And the corresponding Function it uses:
public class waitForElement implements Function<WebDriver, Boolean> {
private final By by;
private String text = null;
public waitForElement( By by ) {
this.by = by;
}
public waitForElement( By by, String text ) {
this.by = by;
this.text = text;
}
#Override
public Boolean apply( WebDriver from ) {
if( this.text != null ) {
for( WebElement e : from.findElements( this.by ) ) {
if( e.getText().equals( this.text ) ) {
return Boolean.TRUE;
}
}
return Boolean.FALSE;
} else {
try {
from.findElement( this.by );
} catch( Exception e ) {
return Boolean.FALSE;
}
return Boolean.TRUE;
}
}
}
I realise that you're using Selenium in Ruby but hopefully some of my code (at least conceptually) is transferable and helpful to you.
Monitoring the value, returned driver.get_location did the job perfectly to me.
Apparently, from what I've understood in my 5 mins peeping into the code was that window.location.href value is monitored under the hood.
You can use this function, it will re-load the current page ( after was redirected):
driver.getCurrentUrl();