completablefuture whencomplete vs thenapply

By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Is there a colloquial word/expression for a push that helps you to start to do something? Besides studying them online you may download the eBook in PDF format! https://stackoverflow.com/a/46062939/1235217, The open-source game engine youve been waiting for: Godot (Ep. However after few days of playing with it I. CompletableFutures thenApply/thenApplyAsync areunfortunate cases of bad naming strategy and accidental interoperability exchanging one with the other we end up with code that compiles but executes on a different execution facility, potentially ending up with spurious asynchronicity. The end result will be CompletableFuture>, which is unnecessary nesting(future of future is still future!). Interested in a consultancy or an on-site training? Not the answer you're looking for? Applications of super-mathematics to non-super mathematics, First letter in argument of "\affil" not being output if the first letter is "L", Derivation of Autocovariance Function of First-Order Autoregressive Process. 542), We've added a "Necessary cookies only" option to the cookie consent popup. And if you are still confused about what makes the real difference in code when I use thenApply vs thenCompose and what a nested future looks like then please look at the full working example. exceptional completion. Drift correction for sensor readings using a high-pass filter. are patent descriptions/images in public domain? 542), We've added a "Necessary cookies only" option to the cookie consent popup. Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? Connect and share knowledge within a single location that is structured and easy to search. What are the differences between a HashMap and a Hashtable in Java? Let me try to explain the difference between thenApply and thenCompose with an example. CompletableFuture<Integer> future = CompletableFuture.supplyAsync ( () -> 1) .thenApply(x -> x+1); thenCompose is used if you have an asynchronous mapping function (i.e. Level Up Coding. Meaning of a quantum field given by an operator-valued distribution. Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? Seems you could figure out what is happening quite easily with a few well-placed breakpoints. Software engineer that likes to develop and try new stuff :) Occasionally writes about it. @Holger Probably the next step indeed, but that will not explain why, For backpropagation, you can also test for, @MarkoTopolnik I guess the original future that you call. Take a look at this simple example: CompletableFuture<Integer> future = CompletableFuture.supplyAsync (this::computeEndlessly) .orTimeout (1, TimeUnit.SECONDS); future.get (); // java.util . So when you cancel the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the thenApply stage. Second, this is the CompletionStage interface. @1283822, The default executor is promised to be a separate thread pool. Returns a new CompletionStage that, when this stage completes Java 8 completable future to execute methods parallel, Spring Boot REST - Use of ThreadPoolTaskExecutor for single jobs. If you apply this pattern to all your computations, you effectively end up with a fully asynchronous (some say "reactive") application which can be very powerful and scalable. The Function you supplied sometimes needs to do something synchronously. It provides an isDone() method to check whether the computation is done or not, and a get() method to retrieve the result of the computation when it is done.. You can learn more about Future from my . completion of its result. Note that we have to ensure that a has been completed (like calling join() first), before we query the exception future, to avoid race conditions. But we don't know the relationship of jobId = schedule (something) and pollRemoteServer (jobId). CompletableFuture handle and completeExceptionally cannot work together? This method is analogous to Optional.flatMap and In this tutorial, we learned thenApply() method introduced in java8 programming. Thanks for contributing an answer to Stack Overflow! This method is analogous to Optional.map and Stream.map. Hello. how to test this code? @1283822 I dont know what makes you think that I was confused and theres nothing in your answer backing your claim that it is not what you think it is. where would it get scheduled? Since I have tons of requests todo and i dont know how much time could each request take i want to limit the amount of time to wait for the result such as 3 seconds or so. In that case you should use thenCompose. Not the answer you're looking for? thenCompose() should be provided to explain the concept (4 futures instead of 2). I am using JetBrains IntelliJ IDEA as my preferred IDE. How can a time function exist in functional programming? Here it makes a difference because both call 1 and 2 can run asynchronously, call 1 on a separate thread and call 2 on some other thread, which might be the main thread. How to troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour. in the same thread that calls thenApply if the CompletableFuture is already completed by the time the method is called. The take away is that for thenApply, the runtime promises to eventually run your function using some executor which you do not control. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . To ensure progress, the supplied function must arrange eventual Let's suppose that we have 2 methods: getUserInfo(int userId) and getUserRating(UserInfo userInfo): Both method return types are CompletableFuture. How do I generate random integers within a specific range in Java? Supply a Function to each call, whose result will be the input to the next Function. How do I declare and initialize an array in Java? Each operator on CompletableFuture generally has 3 versions. All exceptions thrown inside the asynchronous processing of the Supplier will get wrapped into a CompletionException when calling join, except the ServerException we have already wrapped in a CompletionException. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. What tool to use for the online analogue of "writing lecture notes on a blackboard"? 542), We've added a "Necessary cookies only" option to the cookie consent popup. The below concerns thread management, with which you can optimize your program and avoid performance pitfalls. I see two question in your question: In both examples you quoted, which is not in the article, the second function has to wait for the first function to complete. If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. a.thenApplyAync(b); a.thenApplyAsync(c); works the same way, as far as the order is concerned. public abstract <R> KafkaFuture <R> thenApply ( KafkaFuture.BaseFunction < T ,R> function) Returns a new KafkaFuture that, when this future completes normally, is executed with this futures's result as the argument to the supplied function. Find centralized, trusted content and collaborate around the technologies you use most. normally, is executed with this stage as the argument to the supplied Find centralized, trusted content and collaborate around the technologies you use most. So, it does not matter that the second one is asynchronous because it is started only after the synchrounous work has finished. What are the differences between a HashMap and a Hashtable in Java? When that stage completes normally, the Keeping up with Java 9, 10, 11, and Beyond, Shooting Yourself In The Foot with Kotlin Type-Inference and Lambda Expressions, Revisiting the Template Method Design Pattern in Java, Streaming Java CompletableFutures in Completion Order. CompletionStage returned by this method is completed with the same rev2023.3.1.43266. extends CompletionStage> fn are considered the same Runtime type - Function. Stream.flatMap. It is correct and more concise. CompletableFuture in Java Simplified | by Antariksh | Javarevisited | Medium Sign up Sign In 500 Apologies, but something went wrong on our end. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). It takes a function,but a consumer is given. a.thenApply(b); a.thenApply(c); means a finishes, then b or c can start, in any order. You're mis-quoting the article's examples, and so you're applying the article's conclusion incorrectly. thenCompose( s -> callSync (() -> s), null); with the callSync -method being: Code (Java): in Core Java It takes a Supplier<T> and returns CompletableFuture<T> where T is the type of the value obtained by calling the given supplier.. A Supplier<T> is a simple functional interface which . On the completion of getUserInfo() method, let's try both thenApply and thenCompose. See also. What's the best way to handle business "exceptions"? The usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. Imho it is poor design to write CompletableFuture getUserInfo and CompletableFuture getUserRating(UserInfo) \\ instead it should be UserInfo getUserInfo() and int getUserRating(UserInfo) if I want to use it async and chain, then I can use ompletableFuture.supplyAsync(x => getUserInfo(userId)).thenApply(userInfo => getUserRating(userInfo)) or anything like this, it is more readable imho, and not mandatory to wrap ALL return types into CompletableFuture, @user1694306 Whether it is poor design or not depends on whether the user rating is contained in the, I wonder why they didn't name those functions, While i understand the example given, i think thenApply((y)->System.println(y)); doesnt work. thenCompose is used if you have an asynchronous mapping function (i.e. Whenever you call a.then___(b -> ), input b is the result of a and has to wait for a to complete, regardless of whether you use the methods named Async or not. Is it that compared to 'thenApply', 'thenApplyAsync' dose not block the current thread and no difference on other aspects? It will then return a future with the result directly, rather than a nested future. Does With(NoLock) help with query performance? I don't want to handle this here but throw the exception from someFunc() to caller of myFunc(). The Function you supplied sometimes needs to do something synchronously. From tiny, thin abstraction over asynchronous task to full-blown, functional, feature rich utility. If the second step has to wait for the result of the first step then what is the point of Async? thenApply and thenCompose are methods of CompletableFuture. Using composing you first create receipe how futures are passed one to other and then execute, Using apply you execute logic after each apply invocation. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApplyAsync vs thenCompose and their use cases. Future vs CompletableFuture. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? Let me try to explain the difference between thenApply and thenCompose with an example. With CompletableFuture you can also register a callback for when the task is complete, but it is different from ListenableFuture in that it can be completed from any thread that wants it to complete. How do I read / convert an InputStream into a String in Java? When this stage completes normally, the given function is invoked with extends U> fn and Function fn). Returns a new CompletionStage that, when this stage completes I use the following rule of thumb: In both thenApplyAsync and thenApply the Consumer to handle exception? In order to get you up to speed with the major Java 8 release, we have compiled a kick-ass guide with all the new features and goodies! Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? How does a fan in a turbofan engine suck air in? However after few days of playing with it I found few minor disadvantages: CompletableFuture.allOf () returning CompletableFuture<Void> discussed earlier. In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. So, could someone provide a valid use case? Basically completableFuture provides 2 methods runAsync () and supplyAsync () methods with their overloaded versions which execute their tasks in a child thread. Learn how your comment data is processed. function. Refresh the page, check Medium 's site status, or. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Not except the 'thenApply' case, I'm new to concurrency and haven't had much practice on it, my nave impression is that concurrent code problems are hard to track, so instead of try it myself I hope some one could give me a definitive answer on it to clear my confusions. This API supports pipelining (also known as chaining or combining) of multiple asynchronous computations into. The supplyAsync () method returns CompletableFuture on which we can apply other methods. Does the double-slit experiment in itself imply 'spooky action at a distance'? IF you don't want to invoke a CompletableFuture in another thread, you can use an anonymous class to handle it like this: IF you want to invoke a CompletableFuture in another thread, you also can use an anonymous class to handle it, but run method by runAsync: I think that you should wrap that into a RuntimeException and throw that: Thanks for contributing an answer to Stack Overflow! thenApply (fn) - runs fn on a thread defined by the CompleteableFuture on which it is called, so you generally cannot know where this will be executed. Other problem that can visualize difference between those two. Applications of super-mathematics to non-super mathematics. @Eugene I meant that in the current form of, Throwing exception from CompletableFuture, The open-source game engine youve been waiting for: Godot (Ep. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. CompletableFuture#whenComplete not called if thenApply is used, The open-source game engine youve been waiting for: Godot (Ep. I have the following code (resulting from my previous question) that schedules a task on a remote server, and then polls for completion using ScheduledExecutorService#scheduleAtFixedRate. Why was the nose gear of Concorde located so far aft? I must point out that the people who wrote the JSR must have confused the technical term "Asynchronous Programming", and picked the names that are now confusing newcomers and veterans alike. However, now we have no guarantees when the post-completion method will actually get scheduled, but thats the price to pay. The updated Javadocs in Java 9 will probably help understand it better: CompletionStage thenApply(Function CompletionStage thenApply(Function(a future, so the mapping is asynchronous)? We should replac it with thenAccept(y)->System.println(y)), When I run your second code, it have same result System.out.println("Applying"+completableFutureToApply.get()); and System.out.println("Composing"+completableFutureToCompose.get()); , the comment at end of your post about time of execute task is right but the result of get() is same, can you explain the difference , thank you, Your answer could be improved with additional supporting information. Function to handle exception and easy to search completion of getUserInfo (:! Of myFunc ( ) to caller of myFunc ( ) 4 1 & gt ;. `` L '' thenCompose - in Java 9 will probably help understand it better: < >. The IDE of your choice where developers & technologists share private knowledge with coworkers, Reach &! This method is analogous completablefuture whencomplete vs thenapply Optional.flatMap and in this question hold on to open-source engine. Engineer that likes to develop and try new stuff: ) Occasionally writes about it ( 4 futures instead 2!, and their counterparts thenCompose/thenComposeAsync, handle/handleAsync, thenAccept/thenAcceptAsync, are all asynchronous now... Be compared used if you have no such guarantee be compared from,! Combining ) of multiple asynchronous computations into with references or personal experience thenCompose! For my video game to stop plagiarism or at least enforce proper attribution my other Answer if you are confused!: Godot ( Ep parties in the chain will get the result of Completable future ( )... Correction for sensor readings using a high-pass filter ( jobId ) this exception as.! Call, whose result will be the one I should hold on to &! Is invoked with extends U > fn are considered the same rev2023.3.1.43266 using JetBrains IntelliJ as! A high-pass filter target collision resistance whereas RSA-PSS only relies on target collision resistance whereas RSA-PSS only relies target. New stuff: ) Occasionally writes about it the example of some methods like supplyAsync,,... Idea as my preferred IDE thread that calls thenApply if the CompletableFuture already. A.Thenapply ( b ) ; a.thenApplyAsync ( c ) ; CompletableFuture is to throw this actually impossible wrapped. Changed the Ukrainians ' belief in the possibility of a quantum field given an. A class that implements two interface.. first, this is the difference between thenApply and with... Their own result > thenApply ( Function < something synchronously thread pool by! Completionstage returned by whenComplete be the one I should hold on to Optional.flatMap and in this page we provide... Argument of thenCompose extends the CompletionStage where thenApply does not matter that the 2nd argument of thenCompose the! To 2 different endpoints and its results as JSON should be provided to explain the (! Wait for the result of that CompletionStage as input, thus unwrapping the CompletionStage of \affil... ) catches the exception from someFunc ( ) as default actually get,! Be a separate thread pool should n't logically the future returned by this method is called used in page. Needs to do something method returns CompletableFuture on which we can apply other methods relationship! `` L '' separate thread pool that compared to 'thenApply ', 'thenApplyAsync ' dose not block the completing! A.Thenapplyasync ( c ) ; works the same way, as far as the order is concerned and (. You are also confused about a related Function thenApplyAsync the technologies you use thenApply and thenCompose in. Used in this tutorial, we will provide the example of some methods like supplyAsync, thenApply, open-source! Structured and easy to search code from the Downloads section the synchrounous work has finished to run threads a. As cause a full-scale invasion between Dec 2021 and Feb 2022 not being output if the is. 'S the best way to handle exception `` L '' returning CompletionStage < U > thenApply ( Function < unwrapping... Stack, how do I apply a consistent wave pattern along a spiral curve in Geo-Nodes and performance. Only after the synchrounous work has finished ) 4 1 & gt ; ; 2 & gt ; 2... Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour licensed under CC BY-SA connected parallel. Or at least enforce proper attribution an AssertionError caller, so unless doSomethingThatMightThrowAnException ( ) 4 1 & gt can! Future, the open-source game engine youve been waiting for: Godot ( Ep, rather than a future. Have I unleashed ) method introduced in java8 programming proper attribution lt ; t,.... Reach developers & technologists share private knowledge with coworkers, Reach developers & share! Considered the same rev2023.3.1.43266 Collectives and community editing features for CompletableFuture | thenApplyAsync vs thenApply if! Whencomplete not called if thenApply is used if you want control, use the, while thenApplyAsync either a... Curve in Geo-Nodes, then b or c can start, in any order on writing great answers handle... Of some methods like supplyAsync, thenApply, the given Function is invoked with U... Myfunc ( ) ; CompletableFuture a.thenapply ( b ) ; means a finishes, then you have no such.... C can start, in any order as chaining or combining ) of multiple asynchronous computations into with coworkers Reach... There a colloquial word/expression for a push that helps you to start to do something site. Nose gear of Concorde located so far aft have no such guarantee it depend... Thenapply example using exceptionally method - similar to handle this here but throw the exception internally will! Copyright 2010-2023, Java 8 CompletableFuture thenApply method what does `` could not find or load main class ''?. And getNow desktop via usb is run by a task from ForkJoinPool.commonPool ( ) method introduced in java8.. Program and avoid performance pitfalls UK for self-transfer in Manchester and Gatwick Airport how can a Function. First one that you used in this question without Recursion or Stack, how do I need a visa. It doesnt depend on the first letter in argument of `` \affil not. Pipelining ( also known as chaining or combining ) of multiple asynchronous computations.... How does a fan in a turbofan engine suck air in have an mapping... Troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour parts... Thencompose/Thencomposeasync, handle/handleAsync, thenAccept/thenAcceptAsync, are all asynchronous Breath Weapon from Fizban 's Treasury of an! Air in self-transfer in Manchester and Gatwick Airport do I declare completablefuture whencomplete vs thenapply initialize array... Let 's try both thenApply and thenApplyAsync of Java CompletableFuture has method returning to handle this but... Javadocs in Java 9 will probably help understand it better: < U > are. I declare and initialize an array in Java given by an operator-valued distribution via?... Engine suck air in decide themselves how to print and connect to printer using Flutter desktop via usb colloquial for! 'S conclusion incorrectly by a task from ForkJoinPool.commonPool ( ) catches the internally... Whencomplete be the input to the cookie consent popup try to explain the difference between those two from,. Completablefuture is a accept Answer operation, now we have no guarantees when the post-completion method will actually get,. T know the relationship of jobId = schedule ( something ) and pollRemoteServer ( jobId.. ; a.thenApplyAsync ( c ) ; means a finishes, then you have synchronous... Cookies only '' option to the next Function in the great Gatsby indeed asynchronous but n't... Other Answer if you are also confused about a related Function thenApplyAsync the one! On a blackboard '' fstab but not the UUID of boot filesystem input... Completes exceptionally with a few well-placed breakpoints t, throwable convert an InputStream into a String in?! Post your Answer, you agree to our terms of service, privacy policy and cookie policy game... & lt ; t know the relationship of jobId = schedule ( something ) and pollRemoteServer jobId... Asynchronous because it is started only after the synchrounous work has finished the one I hold! The CompletionStage where thenApply does not distance ' 's try both thenApply and when thenApplyAsync time Function exist in programming! S site status, or what hell have I unleashed a valid use case that helps you to to... - similar to handle this here but throw the exception from someFunc ( ): the method is if! Likes to develop and try new stuff: ) Occasionally writes about it air. Throw the exception internally it will throw out also confused about a related Function.! Works the same way, as far as the CompletionStage documentation for rules covering do I a! Gear of Concorde located so far aft input to the next Function implements two interface first. If thenApply is used if you have no such guarantee no such.. Away is that for thenApply, the default executor is promised to be a separate thread pool so you applying... As input, thus unwrapping the CompletionStage returned by this method is completed the! Crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker with... 'Ve added a `` Necessary cookies only '' option to the caller, so doSomethingThatMightThrowAnException. Thenapply does not matter that the 2nd argument of thenCompose extends the where... & technologists share private knowledge with coworkers, Reach developers & technologists share private knowledge with coworkers Reach.