Java mono subscribe return value This problem is very hard to describe as text, so if the title doesn't fit the requirement, sorry for that. Asking for help, clarification, or responding to other answers. Use Mono's content within a reactive pipeline. I would like to achieve a specific goal with Project Reactor flux and mono, which seems to be pretty simple at first look. setName(v), throwable -> {}, -> System. Is there a way the mono. Provide details and share your research! But avoid . And, of course, it There are high risks when letting null into an application/library, and if you can ban it, one should. This abstract code improves code reusability and How is a Boolean value extracted from a Mono<Boolean> type value? Is it possible to extract the value out from the Mono<Boolean> field? I tried working with subscribe() but could not get it to return a value to me evaluate. setExternalId(id); return entity; }); I have a problem when I try to execute a Mono inside doFinally clause. In case the Mono errors, the original exception is thrown (wrapped in a RuntimeException if it was a checked exception). I am connecting to sonar to fetch the gate result for a project, once i get the result I must extract value from within response and return (BOOLEAN) TRUE or FALSE. Reactive Java Mono. The following code is a simple example showing how to handle nulls returned by a Location by wrapping getLocation in a Mono. The callback function will be invoked when We handle different callback methods such as onSubscribe, onNext, onError, and onComplete to manage the data stream. fromCallable. return repository. getBalance() >= prd. fromSupplier(() -> "From Supplier"); mono. I want to return id after someFlux has completed. myNumber = number) I also tried with then and subscribe but I can't get the webclient to perform the call and return the result of service. zip with Mono. In case of failure, it Subscribe to this Mono and block indefinitely until a next signal is received. Subscribe to this Mono and block indefinitely until a next signal is received. How do I return the value that is returned by Consumer invoked inside Mono. empty() . subscribe()? 1. 8 its default value is 256. Hot Network Questions Assignments of people Any time you feel the need to transform or map what's in your Mono to something else, then you use the map() method, passing a lambda that will do the transformation like so:. getName())); However, the subscribe() method will return immediately. Java enum: Return value other than String. Also, your Mono need to be consumed. You can create some helper method to do calculation on them. A Mono is a reactive publisher that emits at most one element (0. 7. The consumer will be called asynchronously when the Mono emits a value, with that value as a parameter. I'm new to functional endpoints/spring webflux and I'm trying to return mono as a header value but I couldn't find a way to do it as the header method accepts only the string. Return a Mono<Void> which only listens for complete and error signals from this Mono completes. println(person. subscribe( i -> From the Official Documentation of Mono#block() it is said that:. If the value of getQualityGateStatus() == "OK" i will return TRUE else FALSE. Hot Network Questions Type Parameters: T1 - type of the value from source1 T2 - type of the value from source2 T3 - type of the value from source3 T4 - type of the value from source4 T5 - type of the value from source5 T6 - type of the value from source6 Parameters: p1 - The first upstream Publisher to subscribe to. myMono. Example: Install Java Development Kit (JDK): Make sure you have JDK 8 or later installed Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. bodyToFlux(Employee. The very point of that callback is that the result cannot be provided to the caller; instead, the result will occur some time later. getId()) . Consume Mono value and use it to call another Mono. This means it can emit only one value at most for the onNext() request and then terminates with the onComplete() signal. uri("/employees") . null creates an enormous uncertainty in an application at all times. myNumber = number) Case 2: doOnNext someIntegerSource. fromSupplier creates a Mono that emits a value provided One way to handle obtaining an object from a Mono without blocking is by using the subscribe () method with a callback function. If you don't call request(n) on the subscription in the consumer, no data will be emitted and the Mono won't complete. To answer the question directly in its simplest form - you use Mono. The calls will be executed in parallel, results will be combined when both calls are completed. This way of A Mono object represents a single or empty value. map(id -> { //in case of empty stream, i need call entity. This setup ensures that you have the necessary tools and libraries to start developing with Mono. return getUserProfile(serviceName, filterValue) . To create one, you can use an empty Mono<Void>. getPrice(); } And then in your Mono stream you can pass method reference and make it more readable. You should always clean out null as early as possible. block(). Mono is a Publisher from Project Reactor that can emit 0 or 1 item. just(id)) } I. switchIfEmpty(repository. You should, instead, call subscribe() and then provide a consumer. Mono and Flux are both reactive streams. DbSchema is a super-flexible database designer, which can take you from designing the DB with your team all the way to safely deploying the schema. But should you do that? When you mix things (reactive and blocking), things get out of control easily. Use Mono::switchIfEmpty that provides an alternative Mono in case the former one is completed without data. You can define a When mapping a content of Mono using map method, you cannot provide null as a mapping result, because that will result in the java. Here you have private constructor which will initialize the value you want to set and when the instance method value gets invoked simply return this. out::println); Flux<Employee> employeeFlux = client. The Mono can be either empty or it has to contain a valid object. Spring webflux mono subscribe() When you write a Publisher chain, you are actually creating an abstract description of your asynchronous process. return externalClient. doOnNext(number -> this. Subscribe to RSS Question feed To subscribe to this RSS feed, copy and paste this URL into your RSS reader The Mono will not emit data, so doOnNext will not be triggered. In this simple case, you could also valueMono. save(new Category(category. Without the code, we don't know if it is or not. In reactor-core 3. Mono<Integer> userId = savedUserMono. According to the source code of Project Reactor, the content of a Mono cannot I have a list of Rules that return Mono<Result>, I need to execute them and return another List of Mono with the result of each function. out::println); Output: From Supplier. 1). public interface Locks { Mono<ReactiveDistributedLock> doLock(LockParams params); Mono<Bo For example, Mono#concatWith(Publisher) returns a Flux while Mono#then(Mono) returns another Mono. 0. Null is like letting a bomb into your application, if something potentially can be null, then something can explode with a NullPointerException at any time. //returning the value emitted by another Mono employeeMono. ). Try to have callback methods that uses this "val" you are trying to retrieve and pass it to them without breaking the method chain. If the provided timeout expires, a RuntimeException is thrown. map(userProfile -> userProfileToAttributeList(userProfile)); return myService. Yes, just as I show with Console. out. Basically your approach with zipping two monos is correct. You should not block Mono if the return value is Mono as well, use zip instead:. just(new I'm using a non-reactive repository and therefore I need to subscribe to the Mono which contains the entity, in order to save it in the datbase. doOnSuccess(number -> this. Let's say you have Mono<Integer> someIntegerSource = Mono. The maxConcurrency value can be specified as an additional argument to flatMapSequential. There are two ways to extract data from Mono: Blocking; Non-blocking; Extract data from Mono in Java – blocking way. 3. – Alexey Romanov. Depending on the use of your Mono, you will have to do or not the same thing. Mono. Here's an example with (pseudo) code that resembles what I'm after: val myId : Mono<String> = fetchMyId() myId. Commented Nov 8, 2017 at 14:28. As long as ReactiveMongoRepository::save returns Mono, you can pass it to generate the alternative one. p3 - The third upstream I want to have a Mono that calls another async method that returns an Optional type to: have a value if the Optional is not empty, is MonoEmpty if the Optional value is empty. NullPointerException: The mapper returned a null value. Try Teams for free Explore Teams You can wrap the blocking call in a Mono executed on a separate scheduler, zip it with the Mono containing UserState data and transform their combination into a Mono<ModelAndView> (which can be returned from Spring controller methods). just(5) and you want to assign it to a variable. empty() parameters. e. operation1. Commented Nov 8, 2017 at 14:27. So how do I achieve it. get() . I need to run GET requests multiple times until the return of the GET is an empty array. To subscribe to this RSS feed, copy and paste this URL into Subscribe to this Mono and block until a next signal is received or a timeout expires. key. setExternalId(null); entity. getName()))); In case You can't. In case the Mono errors, the original exception is thrown Mono<String> mono = Mono. class DoStuff { Mono<User> getUserById(Long userId){ return Mono. The way it does all of that is by using a design model, a database-independent image of the schema, which can be shared in a team using GIT and compared or deployed on to any database. In your case it may look like: public boolean isAccountBalanceGreater(Account acc, Product prd) { return acc. Ask questions, find answers and collaborate at work with Stack Overflow for Teams. returnOnComplete(Mono. We can use the blocking subscriber to pause the thread execution until we get the data from Mono. getUserProfile(serviceName, filterValue); return There are two ways to extract data from Mono: We can use the blocking subscriber to pause the thread execution until we get the data from Mono. map(user -> user. Some example here: I added subscribe() to consume the mono. fromCallable could change a local variable? A common pattern you find when using reactive java code is handling nulls when collecting a list. findById(category. Transform the terminal signal (error or completion) into Mono<V> that will emit at most one Assuming that you are always returning Mono from your repository methods, you can do this. I'd like to return a value (or publisher) after a Flux is completed. You should use the doOnSuccess instead. You can choose one of the operators provided depending on the case. during the subscription. flatMap { id -> someFlux. But you almost certainly shouldn't, as this blocks the thread, defeating the point of using reactor in the first place. subscribe(System. getId()); (assuming, of course, that your user has a getId() method, and the id is an integer. Is there a difference between these code snippets? Case 1: doOnSuccess someIntegerSource. Immediately return first emitted value from two Monos while continuing to process the other asynchronously. class); . Router function, @Bean java; spring; mono; Returning Mono response from subscribe of Mono. 2. Would like to do with webclient without blocking, i do not want to use rest template. p2 - The second upstream Publisher to subscribe to. To subscribe to this RSS feed, copy That's because the versions of subscribe with a Consumer<Subscription> are meant for you to drive the initial request. getExternalId() //returns Mono<String> or Mono. println in the example. defer then handling a null using onErrorReturn. Can the two reactive statements be combined to form one statement? Any direction you can offer is appreciated. public Mono<User> getUserSummary(int userId) { Mono<Address> addressMono I am calling an external service to get externalId, in case of that service doesn't work, all what i need is just populate the value with null. 1 Return object from mono java stream. Returns that value, or null if the Mono completes empty. Overview. This is my code. Currently I have been doing it with a global receivedAllApiData variable I update in getApiValues if it is an empty array. Yes, it is possible. lang. In this article, we will learn about the Mono subscribe() method of the Spring WebFlux. This works as expected: CountDownLatch latch = new CountDownLatch(3); Mono. However I need to find a way to do this in the method locally. doOnNext { }. Note that you can use a Mono to represent no-value asynchronous processes that only have the concept of completion (similar to a Runnable). retrieve() . . subscribe(value->print(value)) ? – nanosoft. subscribe(v-> person. just(1). map { . }. 1. yxhyf xaez rgjj rcz chj meapuft qeei mjnp gljmyg istzkf