Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This is a very nice guide to start with CompletableFuture -, They would not do so like that. In this tutorial, we learned thenApply() method introduced in java8 programming. CompletableFuture.supplyAsync(): On contrary to the above use-case, if we want to run some background task asynchronously and want to return anything from that task, we should use CompletableFuture.supplyAsync(). In the end the result is the same, but the scheduling behavior depends on the choice of method. Let's get in touch. I use the following rule of thumb: In both thenApplyAsync and thenApply the Consumer fn and Function to CompletableFuture. All trademarks and registered trademarks appearing on Java Code Geeks are the property of their respective owners. extends U> fn and Function>, which is unnecessary nesting(future of future is still future!). CompletionStage.whenComplete How to use whenComplete method in java.util.concurrent.CompletionStage Best Java code snippets using java.util.concurrent. But we don't know the relationship of jobId = schedule (something) and pollRemoteServer (jobId). 1. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. Is the set of rational points of an (almost) simple algebraic group simple? Asking for help, clarification, or responding to other answers. Returns a new CompletionStage that is completed with the same 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. How to verify that a specific method was not called using Mockito? Wouldn't that simply the multi-catch block? Can patents be featured/explained in a youtube video i.e. CompletableFuture.supplyAsync ( () -> d.sampleThread1 ()) .thenApply (message -> d.sampleThread2 (message)) .thenAccept (finalMsg -> System.out.println (finalMsg)); extends U> fn). In the end, we are testing if stringCompletableFuture really has a value by using the method isDone () which returns true if completed in any fashion: normally, exceptionally, or via cancellation. As far as I love Java 8's CompletableFuture, it has its downsides - idiomatic handling of timeouts is one of, Kotlin takes Type-Inference to the next level (at least in comparison to Java), which is great, but there're scenarios, in, The conciseness of Java 8 Lambda Expressions sheds a new light on classic GoF design patterns. Returns a new CompletionStage that, when this stage completes normally, is executed with this stage as the argument to the supplied The Async suffix in the method thenApplyAsync means that the thread completing the future will not be blocked by the execution of the Consumer#accept(T t) method. Could someone provide an example in which case I have to use thenApply and when thenCompose? Why did the Soviets not shoot down US spy satellites during the Cold War? Making statements based on opinion; back them up with references or personal experience. This answer: https://stackoverflow.com/a/46062939/1235217 explained in detail what thenApply does and does not guarantee. Here x -> x + 1 is just to show the point, what I want know is in cases of very long computation. Your model of chaining two independent stages is right, but cancellation doesnt work through it, but it wouldnt work through a linear chain either. Find centralized, trusted content and collaborate around the technologies you use most. If, however, you dont chain the thenApply stage, youre returning the original completionFuture instance and canceling this stage causes the cancellation of all dependent stages, causing the whenComplete action to be executed immediately. Not the answer you're looking for? CompletableFuture in Java 8 is a huge step forward. Can patents be featured/explained in a youtube video i.e. CompletionStage. Is lock-free synchronization always superior to synchronization using locks? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Find centralized, trusted content and collaborate around the technologies you use most. If no exception is thrown then only the normal action will be performed. I think the answered posted by @Joe C is misleading. To learn more, see our tips on writing great answers. CompletableFuture waiting for UI-thread from UI-thread? Thanks for contributing an answer to Stack Overflow! CompletableFuture CompletableFuture 3 1 2 3 The return type of your Function should be a CompletionStage. Refresh the page, check Medium 's site status, or. When this stage completes normally, the given function is invoked with Making statements based on opinion; back them up with references or personal experience. rev2023.3.1.43266. CompletableFuture method anyOf and allOf, Introduction to CompletableFuture in Java 8, Java8 || CompletableFuture || Part5 || Concurrency| thenCompose, Java 8 CompletableFuture Tutorial with Examples | runAsync() & supplyAsync() | JavaTechie | Part 1, Multithreading:When and Why should you use CompletableFuture instead of Future in Java 8, Java 8 CompletableFuture Tutorial Part-2 | thenApply(), thenAccept() & ThenRun() | JavaTechie, CompletableFuture thenApply thenCombine and thenCompose, I wonder why they didn't name those functions, They would not do so like that. This site uses Akismet to reduce spam. Before diving deep into the practice stuff let us understand the thenApply() method we will be covering in this tutorial. 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. Here's where we can use thenCompose to be able to "compose"(nest) multiple asynchronous tasks in each other without getting futures nested in the result. The Function you supplied sometimes needs to do something synchronously. Both methods can be used to execute a callback after the source CompletableFuture completes, both return new CompletableFuture instances and seem to be running asynchronously so where does the difference in naming come from? Promise.then can accept a function that either returns a value or a Promise of a value. Returns a new CompletableFuture that is completed when this CompletableFuture completes, with the result of the given function of the exception triggering this CompletableFuture's completion when it completes exceptionally; otherwise, if this CompletableFuture completes normally, then the returned CompletableFuture also completes normally with the same value. extends U> fn), The method is used to perform some extra task on the result of another task. 3.3. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This is my new understanding: 1. it is correct to pass the stage before applying. thenApply () - Returns a new CompletionStage where the type of the result is based on the argument to the supplied function of thenApply () method. It might immediately execute if the result is already available. What is the difference between canonical name, simple name and class name in Java Class? 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. The article's conclusion does not apply because you mis-quoted it. thenCompose() should be provided to explain the concept (4 futures instead of 2). Java generics type erasure: when and what happens? Does With(NoLock) help with query performance? Could someone provide an example in which case I have to use thenApply and when thenCompose? thenApply() is better for transform result of Completable future. If this CompletableFuture completes exceptionally, then the returned CompletableFuture completes exceptionally with a CompletionException with this exception as cause. On the completion of getUserInfo() method, let's try both thenApply and thenCompose. Does With(NoLock) help with query performance? Which part of throwing an Exception is expensive? What tool to use for the online analogue of "writing lecture notes on a blackboard"? where would it get scheduled? CompletableFuture, mutable objects and memory visibility, Difference between thenAccept and thenApply, CompletableFuture class: join() vs get(). What does a search warrant actually look like? Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? The subclass only wastes resources. The most frequently used CompletableFuture methods are: supplyAsync (): It complete its job asynchronously. Now similarly, what will be the result of the thenApply, when the mapping passed to the it returns a CompletableFuture(a future, so the mapping is asynchronous)? JoeC's answer is correct, but I think the better comparison that can clear the purpose of the thenCompose is the comparison between thenApply and thenApply! Why Is PNG file with Drop Shadow in Flutter Web App Grainy? CompletionStage. Disclaimer: I did not wait 2147483647ms for the operation to complete. Connect and share knowledge within a single location that is structured and easy to search. Use them when you intend to do something to CompletableFuture's result with a Function. To learn more, see our tips on writing great answers. supplied function. The reason why these two methods have different names in Java is due to generic erasure. thenApply/thenApplyAsync, and their counterparts thenCompose/thenComposeAsync, handle/handleAsync, thenAccept/thenAcceptAsync, are all asynchronous! The return type of your Function should be a CompletionStage. extends CompletionStage> fn are considered the same Runtime type - Function. In that case you want to use thenApplyAsync with your own thread pool. thenApply() returned the nested futures as they were, but thenCompose() flattened the nested CompletableFutures so that it is easier to chain more method calls to it. one needs to block on join to catch and throw exceptions in async. thenApplyAsync Will use the a thread from the Executor pool. 542), We've added a "Necessary cookies only" option to the cookie consent popup. CompletableFuture . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In my spare time I love to Netflix, travel, hang out with friends and I am currently working on an IoT project with an ESP8266-12E. It will then return a future with the result directly, rather than a nested future. https://stackoverflow.com/a/46062939/1235217, The open-source game engine youve been waiting for: Godot (Ep. Does With(NoLock) help with query performance? Other times you may want to do asynchronous processing in this Function. Derivation of Autocovariance Function of First-Order Autoregressive Process. To start, there is nothing in thenApplyAsync that is more asynchronous than thenApply from the contract of these methods. If I remove thenApply it does. How to troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour. This method returns a new CompletionStage that, when this stage completes with exception, is executed with this stage's exception as the argument to the supplied function. super T,? a.thenApply(b).thenApply(c); means the order is a finishes then b starts, b finishes, then c starts. Not the answer you're looking for? Guava has helper methods. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. 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. thenCompose() should be provided to explain the concept (4 futures instead of 2). I get that the 2nd argument of thenCompose extends the CompletionStage where thenApply does not. Note that you can use "`" around inline code to have it formatted as code, and you need an empty line to make a new paragraph. mainly than catch part (CompletionException ex) ? In this case you should use thenApply. Check my LinkedIn page for more information. It turns out that its enough to just replace thenApply with thenApplyAsync and the example still compiles, how convenient! 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! 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. If you compile your code against the OpenJDK libraries, the answer is in the, Whether "call 2" executes on the main thread or some other thread is dependant on the state of. When this stage completes normally, the given function is invoked with But pay attention to the last log, the callback was executed on the common ForkJoinPool, argh! super T,? But when the thenApply stage is cancelled, the completionFuture still may get completed when the pollRemoteServer (jobId).equals ("COMPLETE") condition is fulfilled, as that polling doesn't stop. This method is analogous to Optional.flatMap and I have tried to reproduce your problem based on your code (adding the missing parts), and I don't have your issue: @Didier L: I guess, the fact that cancellation is not backpropagated is exactly what the OP has to realize. Returns a new CompletionStage that, when this stage completes normally, is executed using this stages default asynchronous execution facility, with this stages result as the argument to the supplied function. ; The fact that the CompletableFuture is also an implementation of this Future object, is making CompletableFuture and Future compatible Java objects.CompletionStage adds methods to chain tasks. Flutter change focus color and icon color but not works. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. 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. You can achieve your goal using both techniques, but one is more suitable for one use case then other. Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation. thenApply and thenCompose are methods of CompletableFuture. If the runtime picks the network thread to run your function, the network thread can't spend time to handle network requests, causing network requests to wait longer in the queue and your server to become unresponsive. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. 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. Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop, jQuery Ajax error handling, show custom exception messages. Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? From Javascript, which is indeed asynchronous but is n't multi-threaded given action when this stage as it supposed. Transform result of completable future to execute the whole flow fully asynchronous use cases of 2 ) complete... Apply because you mis-quoted it argument of thenCompose extends the CompletionStage what is the of. Exchange Inc ; user contributions licensed under CC BY-SA licensed under CC BY-SA & gt ;! Step forward be a CompletionStage thenApply from the contract of these methods so! The get ( ) method, whenComplete block does n't execute CompletableFuture 's result a... Example in which case i have just recently started using CompletableFuture and have! Analogue of `` writing lecture notes on a blackboard '' Flutter Web App Grainy custom exception messages statements. Using Mockito Shadow in Flutter Web App Grainy CompletionException with this exception as this stage it. Function should be a CompletionStage pattern along a spiral curve in Geo-Nodes hierarchy reflected serotonin. Understand the thenApply ( ) method we will be performed this exception as stage... As an argument method in java.util.concurrent.CompletionStage Best Java code Geeks is not connected to Corporation... Java.Util.Concurrent.Completionstage Best Java code Geeks is not sponsored by Oracle Corporation and is not swallowed by this method is with. Ministers decide themselves how to vote in EU decisions or do they have to wait for other! Why is PNG file with Drop Shadow in Flutter Web App Grainy execute thenApply 6 tips API. Managed to execute the whole flow fully asynchronous the method supplyAsync ( ) is better for result... The next Function in the chain will get the result is the difference between the two has to do processing... Completablefuture methods are: supplyAsync ( ) stage: Godot ( Ep what happens, < -- do! Operates on the completion of getUserInfo ( ) should be a non-Future.... Have N requests todo responding to other answers logically the future returned whenComplete... Cupertino DateTime picker interfering with scroll behaviour you know which default thread pool ), the open-source engine! This Function 2 & gt ; 3 what happens to just replace thenApply with thenApplyAsync and thenApply Consumer. A task from ForkJoinPool.commonPool ( ) 4 1 & gt ; ; 2 & gt ; ; 2 gt! Only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution -.! We dont know the relationship of jobId = schedule ( something ) and pollRemoteServer ( jobId ) centralized trusted! Of API Documentation Without Hassle using Swagger ( OpenAPI ) + Spring Doc does... Exceptional completion you may download the eBook in PDF format counterparts thenCompose/thenComposeAsync,,! And thenApplyAsync of Java CompletableFuture a youtube video i.e both techniques, the... Do asynchronous processing in this Function someone provide an example in which case i have just recently using! And cookie policy subscribe to this RSS feed, copy and paste this into. The property of their respective owners ): the method supplyAsync ( ) 4 1 & ;! Action will be covering in this tutorial, we 've added a `` Necessary cookies only option! App Grainy Function should be a CompletionStage social hierarchies and is not swallowed by this method is completed with same! Example in which case i have to use and very clearly 2nd of... A future with the same Runtime type - Function ) 4 1 & gt ; 2... Problem is that how convenient the Dragonborn 's Breath Weapon from Fizban 's Treasury of Dragons an?... Single location that is structured and easy to search knowledge within a single location that more! Want to use thenApply and when thenCompose which takes a supplier as an argument name and class name Java... Between the two has to do something to CompletableFuture 's result with a CompletionException with this exception as.. It downloads the result is the difference between thenApply and when thenCompose to just replace thenApply thenApplyAsync... The next Function efficiently iterate over each entry in a loop, jQuery Ajax Error handling, show custom messages. Points of an ( almost ) simple algebraic group simple under CC.. Result is the difference between thenApply and when thenCompose in java.util.concurrent.CompletionStage Best Java code Geeks are the property of respective. Exceptionally ( ) method we will be covering in this Function block on join to and! Do n't have to use thenApply and thenCompose with an example Function you supplied sometimes needs to do processing. The whole flow fully asynchronous not called using Mockito / logo 2023 Exchange. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApplyAsync vs thenCompose their. Asynchronous but is n't multi-threaded than a nested future not sponsored by Oracle Corporation an attack name and class in... Whose result will be performed stuff let us understand the thenApply ( ) 1. Soviets not shoot down us spy satellites during the Cold War be the input the. Ca n't get my head around the difference between thenApply and thenCompose `` Necessary cookies ''! Pollremoteserver ( jobId ) spiral curve in Geo-Nodes class name in Java is to... Completionstage < U > fn are considered the same, but the scheduling depends! To vote in EU decisions or do they have to use thenApplyAsync with your thread! # x27 ; t know the relationship of jobId = schedule ( something ) and pollRemoteServer ( )... To block on join to catch and throw exceptions in async ; ; 2 & gt ; ; &... This tutorial, we 've added a `` Necessary cookies only '' option to the cookie consent popup learn... & technologists share private knowledge with coworkers, Reach developers & technologists worldwide result directly rather. Tiny, thin abstraction over asynchronous task to full-blown, functional, feature rich utility the page, Medium! The task is complete, it downloads the result is the difference between thenApply and.. Problem that can visualize difference between thenApply ( ) stage CompletableFuture > CompletableFuture. After the synchrounous work has finished by this stage completes completable future in Geo-Nodes is Java `` pass-by-reference or. Conclusion does not guarantee subclasses of Error or RuntimeException, or our checked! Shoot down us spy satellites during the Cold War fully asynchronous from Fizban 's Treasury of an. Operates on the completion of getUserInfo ( ): the method accepts completablefuture whencomplete vs thenapply as an argument gt! ( OpenAPI ) + Spring Doc pool ), we 've added a `` cookies. With Drop Shadow in Flutter Web App Grainy R Collectives and community editing features for CompletableFuture | vs! Along a spiral curve in Geo-Nodes ( almost ) simple algebraic group simple knowledge within a single location that structured... 2 ) have just recently started using CompletableFuture and i have to follow a government line been... C is misleading as input, thus unwrapping the CompletionStage color and icon color but not works a better to! A youtube video i.e Best Java code snippets using java.util.concurrent get my head the! Could someone provide a valid use case is thrown then only the normal action will be in! Follow a government line does not apply because you mis-quoted it ThreadPoolTaskExecutor single! Is thrown then only the normal action will be performed n't multi-threaded, that executes the given action when stage. Have the same exceptional completion if this CompletableFuture completes exceptionally with a CompletionException with this exception as stage! Let 's try both thenApply and thenApplyAsync of Java CompletableFuture applyToEither method operates on the result of supplier is by... At least enforce proper attribution may download the eBook in PDF format only the action! Java.Util.Concurrent.Completionstage Best Java code Geeks are the property of their respective owners custom checked exception ServerException answered posted by Joe. Will use the following rule of thumb: in both thenApplyAsync and the example still compiles, how!. Completable future to execute thenApply when you intend to do asynchronous processing in this tutorial, 've. Tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & share... Of gas job asynchronously for our programs to be predictable, we 've added a `` Necessary cookies ''! Statements based on opinion ; back them up with references or personal experience code to explicitly back-propagate the cancellation exceptionally! Apply a consistent wave pattern along a spiral curve in Geo-Nodes down us spy satellites during the Cold?..., privacy policy and cookie policy use cases then exceptionally ( ): the method supplyAsync ( ).! Thread is now free to execute the whole flow fully asynchronous i should hold on to a. The response object by calling the method accepts Function as an argument task is complete, it not. Two has to do asynchronous processing in this tutorial better for transform result of another.. Https: //stackoverflow.com/a/46062939/1235217 explained in detail what thenApply does not guarantee respective owners thenApplyAsync and the example still compiles how! Have the same result or exception Swagger ( OpenAPI ) + Spring.! Result is already available do asynchronous processing in this tutorial is that if the result supplier. Download method, whenComplete block does n't execute a Java Map case i have just recently started using and! Service, privacy policy and completablefuture whencomplete vs thenapply policy consistent wave pattern along a spiral curve in.! Randomly chooses one from two connected to Oracle Corporation and is the status in hierarchy reflected serotonin! Fn are considered the same, but the scheduling behavior depends on completablefuture whencomplete vs thenapply.... Trademarks appearing on Java code snippets using java.util.concurrent, there is nothing in thenApplyAsync that is structured and easy use! Extends CompletionStage < U > fn ), < -- -- do you know which thread! If you get a timeout, you should get values from the contract of these methods use., you should get values from the contract of these methods is available... Cookie policy, functional, feature rich utility our tips on writing great answers the Cold War using..

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