rxjava - getting response and inserting diff parallelly - java

I am using rxjava for parallel processing of two requests using Observable.zip. What I am trying to do is , in one observable say response I am getting one response and in other observable say diff I am trying to get the response and save this difference in DB. The problem is I am not sure how to achieve my requirement as the diff observable is not getting completed if response observable gets the response
Here is what I am doing ...
public ServiceResponse getDummyResponse(ServiceRequest serviceRequest, String prodId){
Observable<ServiceResponse> subInfoDummyObservable = getDummyResonseGenericObservable();
Observable<ServicesDiff> reObservable = getServicesDiffGenericObservable(serviceRequest, prodId);
Observable<ServiceResponse> responseObservable = Observable.zip(
subInfoDummyObservable,
reObservable,
new Func2<ServiceResponse, ServicesDiff, ServiceResponse>() {
#Override
public ServiceResponse call(ServiceResponse serviceResponse, ServicesDiff diffResponse) {
return serviceResponse;
}
}
);
ServiceResponse serviceResponse = responseObservable.toBlocking().single();
return serviceResponse;
}
Observable<ServiceResponse> getDummyResonseGenericObservable() {
return GenericHystrixCommand.toObservable("getDummyResonseGenericObservable", "getDummyResonseGenericObservable", () -> new ServiceResponse(),(t) -> {return null;} );
}
Observable<ServicesDiff> getServicesDiffGenericObservable(ServiceRequest serviceRequest, String prodId) {
return GenericHystrixCommand.toObservable("getServicesDiffGenericObservable", "getServicesDiffGenericObservable", () -> getBothServiceResponses(serviceRequest, prodId),(t) -> {return null;} );
}
public ServicesDiff getBothServiceResponses(ServiceRequest serviceRequest, String prodId) {
Observable<String> service1ResponseObservable = getService1GenericObservable(prodId);
Observable<ServiceResponse> service2ResponseObservable = getService2GenericObservable(serviceRequest, prodId);
Observable<ServicesDiff> observable = Observable.zip(
service1ResponseObservable, service2ResponseObservable,
new Func2<String, ServiceResponse, ServicesDiff>() {
#Override
public ServicesDiff call(String service1Response, ServiceResponse service2Response) {
return aggregate(service1Response, service2Response); // never reaches this point**********
}
}
);
ServicesDiff response = observable.toBlocking().single();
return response;
}
I am inserting the diff to DB in aggregate method but it never reaches to aggregate at all. Please let me know what I am doing wrong here? Thanks.


Observable are a description of how to consume data. In your code sample, you don't subscribe, you don't actually consume the data. You just described how to request, but the subscribe part, the part that trigger the requests, is missing.
So if I rewrite a little your code:
class Aggregate {
Aggregate(String reponse, ServicesDiff diff) {
...
}
}
Observable<String> getService1GenericObservable(String prodId) {
...
}
Observable<ServicesDiff> getServicesDiffGenericObservable(ServiceRequest serviceRequest, String prodId) {
...
}
public Observable<Aggregate> getBothServiceResponses(ServiceRequest serviceRequest, String prodId) {
Observable<String> service1ResponseObservable = getService1GenericObservable(prodId);
Observable<ServiceResponse> service2ResponseObservable = getService2GenericObservable(serviceRequest, prodId);
return Observable<Aggregate> observable = Observable.zip(
service1ResponseObservable, service2ResponseObservable,
new Func2<String, ServiceResponse, ServicesDiff>() {
#Override
public ServicesDiff call(String service1Response, ServiceResponse service2Response) {
return aggregate(service1Response, service2Response);
}
}
);
}
You will just have to do this to access the result aggregate:
getBothServiceResponses(serviceRequest, prodId).subscribe(...)

Related

How to merge multiple vertx web client responses

I am new to vertx and async programming.
I have 2 verticles communicating via an event bus as follows:
//API Verticle
public class SearchAPIVerticle extends AbstractVerticle {
public static final String GET_USEARCH_DOCS = "get.usearch.docs";
#Autowired
private Integer defaultPort;
private void sendSearchRequest(RoutingContext routingContext) {
final JsonObject requestMessage = routingContext.getBodyAsJson();
final EventBus eventBus = vertx.eventBus();
eventBus.request(GET_USEARCH_DOCS, requestMessage, reply -> {
if (reply.succeeded()) {
Logger.info("Search Result = " + reply.result().body());
routingContext.response()
.putHeader("content-type", "application/json")
.setStatusCode(200)
.end((String) reply.result().body());
} else {
Logger.info("Document Search Request cannot be processed");
routingContext.response()
.setStatusCode(500)
.end();
}
});
}
#Override
public void start() throws Exception {
Logger.info("Starting the Gateway service (Event Sender) verticle");
// Create a Router
Router router = Router.router(vertx);
//Added bodyhandler so we can process json messages via the event bus
router.route().handler(BodyHandler.create());
// Mount the handler for incoming requests
// Find documents
router.post("/api/search/docs/*").handler(this::sendSearchRequest);
// Create an HTTP Server using default options
HttpServer server = vertx.createHttpServer();
// Handle every request using the router
server.requestHandler(router)
//start listening on port 8083
.listen(config().getInteger("http.port", 8083)).onSuccess(msg -> {
Logger.info("*************** Search Gateway Server started on "
+ server.actualPort() + " *************");
});
}
#Override
public void stop(){
//house keeping
}
}
//Below is the target verticle should be making the multiple web client call and merging the responses
.
#Component
public class SolrCloudVerticle extends AbstractVerticle {
public static final String GET_USEARCH_DOCS = "get.usearch.docs";
#Autowired
private SearchRepository searchRepositoryService;
#Override
public void start() throws Exception {
Logger.info("Starting the Solr Cloud Search Service (Event Consumer) verticle");
super.start();
ConfigStoreOptions fileStore = new ConfigStoreOptions().setType("file")
.setConfig(new JsonObject().put("path", "conf/config.json"));
ConfigRetrieverOptions configRetrieverOptions = new ConfigRetrieverOptions()
.addStore(fileStore);
ConfigRetriever configRetriever = ConfigRetriever.create(vertx, configRetrieverOptions);
configRetriever.getConfig(ar -> {
if (ar.succeeded()) {
JsonObject configJson = ar.result();
EventBus eventBus = vertx.eventBus();
eventBus.<JsonObject>consumer(GET_USEARCH_DOCS).handler(getDocumentService(searchRepositoryService, configJson));
Logger.info("Completed search service event processing");
} else {
Logger.error("Failed to retrieve the config");
}
});
}
private Handler<Message<JsonObject>> getDocumentService(SearchRepository searchRepositoryService, JsonObject configJson) {
return requestMessage -> vertx.<String>executeBlocking(future -> {
try {
//I need to incorporate the logic here that adds futures to list and composes the compositefuture
/*
//Below is my logic to populate the future list
WebClient client = WebClient.create(vertx);
List<Future> futureList = new ArrayList<>();
for (Object collection : searchRepositoryService.findAllCollections(configJson).getJsonArray(SOLR_CLOUD_COLLECTION).getList()) {
Future<String> future1 = client.post(8983, "127.0.0.1", "/solr/" + collection + "/query")
.expect(ResponsePredicate.SC_OK)
.sendJsonObject(requestMessage.body())
.map(HttpResponse::bodyAsString).recover(error -> {
System.out.println(error.getMessage());
return Future.succeededFuture();
});
futureList.add(future1);
}
//Below is the CompositeFuture logic, but the logic and construct does not make sense to me. What goes as first and second argument of executeBlocking method
/*CompositeFuture.join(futureList)
.onSuccess(result -> {
result.list().forEach( x -> {
if(x != null){
requestMessage.reply(result.result());
}
}
);
})
.onFailure(error -> {
System.out.println("We should not fail");
})
*/
future.complete("DAO returns a Json String");
} catch (Exception e) {
future.fail(e);
}
}, result -> {
if (result.succeeded()) {
requestMessage.reply(result.result());
} else {
requestMessage.reply(result.cause()
.toString());
}
});
}
}
I was able to use the org.springframework.web.reactive.function.client.WebClient calls to compose my search result from multiple web client calls, as against using Future<io.vertx.ext.web.client.WebClient> with CompositeFuture.
I was trying to avoid mixing Springboot and Vertx, but unfortunately Vertx CompositeFuture did not work here:
//This method supplies the parameter for the future.complete(..) line in getDocumentService(SearchRepository,JsonObject)
private List<JsonObject> findByQueryParamsAndDataSources(SearchRepository searchRepositoryService,
JsonObject configJson,
JsonObject requestMessage)
throws SolrServerException, IOException {
List<JsonObject> searchResultList = new ArrayList<>();
for (Object collection : searchRepositoryService.findAllCollections(configJson).getJsonArray(SOLR_CLOUD_COLLECTION).getList()) {
searchResultList.add(new JsonObject(doSearchPerCollection(collection.toString(), requestMessage.toString())));
}
return aggregateMultiCollectionSearchResults(searchResultList);
}
public String doSearchPerCollection(String collection, String message) {
org.springframework.web.reactive.function.client.WebClient client =
org.springframework.web.reactive.function.client.WebClient.create();
return client.post()
.uri("http://127.0.0.1:8983/solr/" + collection + "/query")
.contentType(MediaType.APPLICATION_JSON)
.accept(MediaType.APPLICATION_JSON)
.body(BodyInserters.fromValue(message.toString()))
.retrieve()
.bodyToMono(String.class)
.block();
}
private List<JsonObject> aggregateMultiCollectionSearchResults(List<JsonObject> searchList){
//TODO: Search result aggregation
return searchList;
}
My use case is the second verticle should make multiple vertx web client calls and should combine the responses.
If an API call falls, I want to log the error and still continue processing and merging responses from other calls.
Please, any help on how my code above could be adaptable to handle the use case?
I am looking at vertx CompositeFuture, but no headway or useful example seen yet!

What you are looking for can done with Future coordination with a little bit of additional handling:
CompositeFuture.join(future1, future2, future3).onComplete(ar -> {
if (ar.succeeded()) {
// All succeeded
} else {
// All completed and at least one failed
}
});
The join composition waits until all futures are completed, either with a success or a failure.
CompositeFuture.join
takes several futures arguments (up to 6) and returns a future that is succeeded when all the futures are succeeded, and failed when all the futures are completed and at least one of them is failed
Using join you will wait for all Futures to complete, the issue is that if one of them fails you will not be able to obtain response from others as CompositeFuture will be failed. To avoid this you should add Future<T> recover(Function<Throwable, Future<T>> mapper) on each of your Futures in which you should log the error and pass an empty response so that the future does not fail.
Here is short example:
Future<String> response1 = client.post(8887, "localhost", "work").expect(ResponsePredicate.SC_OK).send()
.map(HttpResponse::bodyAsString).recover(error -> {
System.out.println(error.getMessage());
return Future.succeededFuture();
});
Future<String> response2 = client.post(8887, "localhost", "error").expect(ResponsePredicate.SC_OK).send()
map(HttpResponse::bodyAsString).recover(error -> {
System.out.println(error.getMessage());
return Future.succeededFuture();
});
CompositeFuture.join(response2, response1)
.onSuccess(result -> {
result.list().forEach(x -> {
if(x != null) {
System.out.println(x);
}
});
})
.onFailure(error -> {
System.out.println("We should not fail");
});
Edit 1:
Limit for CompositeFuture.join(Future...) is 6 Futures, in the case you need more you can use: CompositeFuture.join(Arrays.asList(future1, future2, future3)); where you can pass unlimited number of futures.

FlatMap is not being called after a webclient call

I have this function inside a #Service in Spring Webflux and it is called with a list of friends to know if everyone has been joined to a group. If some friends have no group this method calls an API to get its user's information and then calls another API to tag these guys with joined tag false.
#Service
...
public Flux<Boolean> checkUserHaveGroup(final List<String> friends) {
MatchOperation match1 = Aggregation.match(Criteria.where("friends").in(friends).and("status").is("ACTIVE"));
UnwindOperation unwind1 = Aggregation.unwind("friends");
MatchOperation match2 = Aggregation.match(Criteria.where("friends").in(friends));
GroupOperation group1 = Aggregation.group("friends");
TypedAggregation<Group> a = Aggregation.newAggregation(
Group.class,
match1, unwind1, match2, group1);
return this.reactiveMongoTemplate.aggregate(a, FriendInGroup.class)
.map(friendInGroup -> friendInGroup.id)
.collectList()
.map(users -> haveNoGroupsList(users, friends))
.flatMapMany(noGroupUsers -> {
return Flux.fromIterable(noGroupUsers)
.flatMap(pn -> crmService.deleteAttribute(pn, "joinedAGroup"));
});
}
(this method get the user information)
...
public Mono<UserInfo> userInfoById(final String userId) {
return webClient.get()
.uri(uriBuilder -> uriBuilder.path(constants.getByIdPath() + "/{id}")
.build(userId))
.header("auth", tokenService.token())
.exchange()
.flatMap(response -> {
Mono<UserInfo> responseMono;
if (response.statusCode().equals(HttpStatus.UNAUTHORIZED)) {
responseMono = Mono.error(new UnauthorizedException());
} else if (response.statusCode().equals(HttpStatus.OK)) {
responseMono = response.bodyToMono(UserInfoResponse.class)
.flatMap(uir -> Mono.just(uir.getData()));
} else {
responseMono = Mono.error(new UnhandledException());
}
return responseMono;
});
}
...
private Mono<UserInfo> getUserInfo(String userId) {
return userInfoAdapter.userInfoById(userId);
}
...
public Mono<Boolean> deleteAttribute(final String userId, final String attribute) {
return getUserInfo(userId) <<<<< here we get the users info
.flatMap(ui -> crmDeleteAttribute(ui, attribute)); <<<< this call is never done.
}
...
public Mono<Boolean> crmDeleteAttribute(final UserInfo user, final String attribute) {
return webClient.delete()
.uri(uriBuilder -> uriBuilder
.path(contants.path())
.build(user.getId(), attribute))
.header("auth", tokenService.token())
.exchange().flatMap(response -> {
if (response.statusCode().equals(HttpStatus.OK)) {
return Mono.just(Boolean.TRUE);
}
if (response.statusCode().equals(HttpStatus.BAD_REQUEST)) {
return Mono.error(CrmServiceBadRequestException::new);
}
if (response.statusCode().equals(HttpStatus.UNAUTHORIZED)) {
return Mono.error(CrmServiceUnauthorizedException::new);
}
return Mono.error(CrmServiceUnhandledException::new);
});
}
After getting the users' info on the API, the API for assign a tag is never been called no matter what I do. I can see in the debugger terminal that the call to UserInfo API was done but after that, the application returns to the controller. Someone could point me to what I'm doing wrong?
Any help is welcome.
Thanks!

“Wanted but not invoked; However there were other interactions with this mock” error

The unit test keeps giving me =
Wanted but not invoked: However, there were exactly 3 interactions with this mock.
All I am trying to do is, testing the timeout for a method execution - if the method takes more time, then terminate it and publish count(to understand the timed out response rate) as metric.
#Test
public void testTimeoutFunction() throws Exception {
Response response = getResponseForTest();
when(processor
.process(any(Request.class)))
.thenAnswer((Answer<Response>) invocation -> {
Thread.sleep(100);
return response;
});
when(itemRequest.getRequestContext()).thenReturn(itemRequestContext);
testClass = spy(new TestClass(processor, executorService));
List<Item> output = testClass.getItemList(ID, itemRequest);
verify(testClass, times(1)).responseTimedOutCount();
assertTrue(output.isEmpty());
verify(testClass, timeout(EXECUTION_TIMEOUT)).buildResponse(itemRequest);
verify(testClass, times(1)).buildResponse(itemRequest);
}
This is method which I am testing for:
public class TestClass {
#VisibleForTesting
void responseTimedOutCount() {
//log metrics
}
private CompletableFuture<Response> getResponseAsync(final ScheduledExecutorService delayer,
final ItemRequest itemRequest) {
return timeoutWithTimeoutFunction(delayer, EXECUTION_TIMEOUT, TimeUnit.MILLISECONDS,
CompletableFuture.supplyAsync(() -> getResponseWithTimeoutFunction(itemRequest), executorService),
Response.emptyResponse(), () -> responseTimedOutCount());
}
private Response getResponseWithTimeoutFunction(final ItemRequest itemRequest) {
//do something and return response
}
public List<Item> getItemList(final String id, final ItemRequest itemRequest) throws Exception {
final ScheduledExecutorService delayer = Executors.newScheduledThreadPool(1);
Response response;
if(validateItemId(id){
try {
response = getResponseAsync(delayer, itemRequest).get();
} catch (final Throwable t) {
response = Response.emptyResponse();
} finally {
delayer.shutdown();
}
return transform(response, id).getItems();
} else {
return null;
}
}
}
Exception from Junit :
For this assert -
verify(testClass, times(1)).responseTimedOutCount();
Wanted but not invoked:
testClass.responseTimedOutCount();
However, there were exactly 3 interactions with this mock:
testClass.getItemList(ID, itemRequest);
testClass.validateItemId(ID);
testClass.getResponseWithTimeoutFunction(itemRequest);

onErrorInsertItem for RxJava 2? Advanced rx cache logic

I'm working on cache implementation with RxJava 2. What I need is when network request fails, my repository would insert stale data and show error message. While I'm able to insert Item with .onErrorReturnItem(cachedItem) the error gets lost. Also I'm able to concat cached data with network request, but it is a bit cumbersome:
public Observable<Dashboard> getDashboard(String phoneNum, boolean getNewData) {
if (getNewData) invalidateDashboardCache();//just set dashboardCacheValid = false
Observable<Dashboard> observableToCache = Observable.fromCallable(
() -> {
Dashboard cached = mCache.getDashboard(phoneNum);
if (cached != null) {
if (!cached.cacheValid()) {
dashboardCacheValid = false;
}
return cached;
}
dashboardCacheValid = false;
return Dashboard.EMPTY;
})
.concatMap(cachedDashboard -> Observable.concat(Observable.just(cachedDashboard),
Observable.fromCallable(() -> !dashboardCacheValid)
.filter(Boolean::booleanValue)
.flatMap(cacheNotValid -> mNetworkHelper.getDashboardRaw(phoneNum))
.doOnNext(dashboard -> {
mCache.putDashboard(pnumber, dashboard);
dashboardCacheValid = true;
})));
return cacheObservable(CACHE_PREFIX_GET_DASHBOARD + phoneNum, observableToCache); //this is for multiple calls
}
Is there a way to modify .onErrorReturnItem(cachedDashboard) to something like this?:

Thanks to #akarnokd I was able to solve it properly and with much cleaner code:
public Observable<Dashboard> getDashboardNew(String phoneNum, boolean getNewData) {
Dashboard fromCache = mCache.getDashboard(phoneNum, getNewData);
dashboardCacheValid = fromCache.cacheValid();
if (getNewData) invalidateDashboardCache();
if (dashboardCacheValid) {
return Observable.just(fromCache);
} else {
final Dashboard cached = fromCache;
Observable<Dashboard> observableToCache = mNetworkHelper.getDashboardRaw(phoneNum)
.doOnNext(dashboard -> mCache.putDashboard(phoneNum, dashboard))
.onErrorResumeNext(throwable -> {
return Observable.concat(Observable.just(cached), Observable.error(throwable));
});
return cacheObservable(CACHE_PREFIX_GET_DASHBOARD + phoneNum, observableToCache);
}
}

Rxjava Android how to use the Zip operator

I am having a lot of trouble understanding the zip operator in RxJava for my android project.
Problem
I need to be able to send a network request to upload a video
Then i need to send a network request to upload a picture to go with it
finally i need to add a description and use the responses from the previous two requests to upload the location urls of the video and picture along with the description to my server.
I assumed that the zip operator would be perfect for this task as I understood we could take the response of two observables (video and picture requests) and use them for my final task.
But I cant seem to get this to occur how I envision it.
I am looking for someone to answer how this can be done conceptually with a bit of psuedo code.
Thank you

Zip operator strictly pairs emitted items from observables. It waits for both (or more) items to arrive then merges them. So yes this would be suitable for your needs.
I would use Func2 to chain the result from the first two observables.
Notice this approach would be simpler if you use Retrofit since its api interface may return an observable. Otherwise you would need to create your own observable.
// assuming each observable returns response in the form of String
Observable<String> movOb = Observable.create(...);
// if you use Retrofit
Observable<String> picOb = RetrofitApiManager.getService().uploadPic(...),
Observable.zip(movOb, picOb, new Func2<String, String, MyResult>() {
#Override
public MyResult call(String movieUploadResponse, String picUploadResponse) {
// analyze both responses, upload them to another server
// and return this method with a MyResult type
return myResult;
}
}
)
// continue chaining this observable with subscriber
// or use it for something else

A small example:
val observableOne = Observable.just("Hello", "World")
val observableTwo = Observable.just("Bye", "Friends")
val zipper = BiFunction<String, String, String> { first, second -> "$first - $second" }
Observable.zip(observableOne, observableTwo, zipper)
.subscribe { println(it) }
This will print:
Hello - Bye
World - Friends
In BiFunction<String, String, String> the first String the type of the first observable, the second String is the type of the second observable, the third String represents the type of the return of your zipper function.
I made a small example that calls two real endpoints using zip in this blog post

Here I have an example that I did using Zip in asynchronous way, just in case you´re curious
/**
* Since every observable into the zip is created to subscribeOn a diferent thread, it´s means all of them will run in parallel.
* By default Rx is not async, only if you explicitly use subscribeOn.
*/
#Test
public void testAsyncZip() {
scheduler = Schedulers.newThread();
scheduler1 = Schedulers.newThread();
scheduler2 = Schedulers.newThread();
long start = System.currentTimeMillis();
Observable.zip(obAsyncString(), obAsyncString1(), obAsyncString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Async in:", start, result));
}
/**
* In this example the the three observables will be emitted sequentially and the three items will be passed to the pipeline
*/
#Test
public void testZip() {
long start = System.currentTimeMillis();
Observable.zip(obString(), obString1(), obString2(), (s, s2, s3) -> s.concat(s2)
.concat(s3))
.subscribe(result -> showResult("Sync in:", start, result));
}
public void showResult(String transactionType, long start, String result) {
System.out.println(result + " " +
transactionType + String.valueOf(System.currentTimeMillis() - start));
}
public Observable<String> obString() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obString1() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obString2() {
return Observable.just("")
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
public Observable<String> obAsyncString() {
return Observable.just("")
.observeOn(scheduler)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "Hello");
}
public Observable<String> obAsyncString1() {
return Observable.just("")
.observeOn(scheduler1)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> " World");
}
public Observable<String> obAsyncString2() {
return Observable.just("")
.observeOn(scheduler2)
.doOnNext(val -> {
System.out.println("Thread " + Thread.currentThread()
.getName());
})
.map(val -> "!");
}
You can see more examples here https://github.com/politrons/reactive

zip operator allow you to compose a result from results of two different observable.
You 'll have to give am lambda that will create a result from datas emitted by each observable.
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<Response> response = movies.zipWith(picture, (movie, pic) -> {
return new Response("description", movie.getName(), pic.getUrl());
});

i have been searching for a simple answer on how to use the Zip operator, and what to do with the Observables i create to pass them to it, i was wondering if i should call subscribe() for every observable or not, non of these answers were simple to find, i had to figure it out by my self, so here is a simple example for using Zip operator on 2 Observables :
#Test
public void zipOperator() throws Exception {
List<Integer> indexes = Arrays.asList(0, 1, 2, 3, 4);
List<String> letters = Arrays.asList("a", "b", "c", "d", "e");
Observable<Integer> indexesObservable = Observable.fromIterable(indexes);
Observable<String> lettersObservable = Observable.fromIterable(letters);
Observable.zip(indexesObservable, lettersObservable, mergeEmittedItems())
.subscribe(printMergedItems());
}
#NonNull
private BiFunction<Integer, String, String> mergeEmittedItems() {
return new BiFunction<Integer, String, String>() {
#Override
public String apply(Integer index, String letter) throws Exception {
return "[" + index + "] " + letter;
}
};
}
#NonNull
private Consumer<String> printMergedItems() {
return new Consumer<String>() {
#Override
public void accept(String s) throws Exception {
System.out.println(s);
}
};
}
the printed result is :
[0] a
[1] b
[2] c
[3] d
[4] e
the final answers to the questions that where in my head were as follows
the Observables passed to the zip() method just need to be created only, they do not need to have any subscribers to them, only creating them is enough ... if you want any observable to run on a scheduler, you can specify this for that Observable ... i also tried the zip() operator on Observables where they should wait for there result, and the Consumable of the zip() was triggered only when both results where ready (which is the expected behavior)

This is my implementation using Single.zip and rxJava2
I tried to make it as easy to understand as possible
//
// API Client Interface
//
#GET(ServicesConstants.API_PREFIX + "questions/{id}/")
Single<Response<ResponseGeneric<List<ResponseQuestion>>>> getBaseQuestions(#Path("id") int personId);
#GET(ServicesConstants.API_PREFIX + "physician/{id}/")
Single<Response<ResponseGeneric<List<ResponsePhysician>>>> getPhysicianInfo(#Path("id") int personId);
//
// API middle layer - NOTE: I had feedback that the Single.create is not needed (but I haven't yet spent the time to improve it)
//
public Single<List<ResponsePhysician>> getPhysicianInfo(int personId) {
return Single.create(subscriber -> {
apiClient.getPhysicianInfo(appId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponsePhysician>> responseBody = response.body();
if(responseBody != null && responseBody.statusCode == 1) {
if (!subscriber.isDisposed()) subscriber.onSuccess(responseBody.data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
public Single<List<ResponseQuestion>> getHealthQuestions(int personId){
return Single.create(subscriber -> {
apiClient.getBaseQuestions(personId)
.subscribeOn(Schedulers.io())
.observeOn(Schedulers.io())
.subscribe(response -> {
ResponseGeneric<List<ResponseQuestion>> responseBody = response.body();
if(responseBody != null && responseBody.data != null) {
if (!subscriber.isDisposed()) subscriber.onSuccess(response.body().data);
} else if(response.body() != null && response.body().status != null ){
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.body().status));
} else {
if (!subscriber.isDisposed()) subscriber.onError(new Throwable(response.message()));
}
}, throwable -> {
throwable.printStackTrace();
if(!subscriber.isDisposed()) subscriber.onError(throwable);
});
});
}
//please note that ResponseGeneric is just an outer wrapper of the returned data - common to all API's in this project
public class ResponseGeneric<T> {
#SerializedName("Status")
public String status;
#SerializedName("StatusCode")
public float statusCode;
#SerializedName("Data")
public T data;
}
//
// API end-use layer - this gets close to the UI so notice the oberver is set for main thread
//
private static class MergedResponse{// this is just a POJO to store all the responses in one object
public List<ResponseQuestion> listQuestions;
public List<ResponsePhysician> listPhysicians;
public MergedResponse(List<ResponseQuestion> listQuestions, List<ResponsePhysician> listPhysicians){
this.listQuestions = listQuestions;
this.listPhysicians = listPhysicians;
}
}
// example of Single.zip() - calls getHealthQuestions() and getPhysicianInfo() from API Middle Layer
private void downloadHealthQuestions(int personId) {
addRxSubscription(Single
.zip(getHealthQuestions(personId), getPhysicianInfo(personId), MergedResponse::new)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(response -> {
if(response != null) {
Timber.i(" - total health questions downloaded %d", response.listQuestions.size());
Timber.i(" - physicians downloaded %d", response.listPhysicians.size());
if (response.listPhysicians != null && response.listPhysicians.size()>0) {
// do your stuff to process response data
}
if (response.listQuestions != null && response.listQuestions.size()>0) {
// do your stuff to process response data
}
} else {
// process error - show message
}
}, error -> {
// process error - show network error message
}));
}

You use the zip from rxjava with Java 8:
Observable<MovieResponse> movies = ...
Observable<PictureResponse> picture = ...
Observable<ZipResponse> response = Observable.zip(movies, picture, ZipResponse::new);
class ZipResponse {
private MovieResponse movieResponse;
private PictureResponse pictureResponse;
ZipResponse(MovieResponse movieResponse, PictureResponse pictureResponse) {
this.movieResponse = movieResponse;
this.pictureResponse = pictureResponse;
}
public MovieResponse getMovieResponse() {
return movieResponse;
}
public void setMovieResponse(MovieResponse movieResponse) {
this.movieResponse= movieResponse;
}
public PictureResponse getPictureResponse() {
return pictureResponse;
}
public void setPictureResponse(PictureResponse pictureResponse) {
this.pictureResponse= pictureResponse;
}
}

You can use .zipWith operator for Observable chains.
If uploadMovies() and uploadPictures() return Observable,
uploadMovies()
.zipWith(uploadPictures()) { m, p ->
"$m with $p were uploaded"
}
.subscribe { print(it) }

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