completablefuture whencomplete vs thenapply

CompletableFuture's thenApply/thenApplyAsync are unfortunate 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. 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. Let me try to explain the difference between thenApply and thenCompose with an example. How do I efficiently iterate over each entry in a Java Map? Since the declared return type of getCause() is Throwable, the compiler requires us to handle that type despite we already handled all possible types. Manually raising (throwing) an exception in Python. 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. completion of its result. 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. CompletableFuture.whenComplete (Showing top 20 results out of 3,231) CompletionStage returned by this method is completed with the same are patent descriptions/images in public domain? 3.3. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It is correct and more concise. Why does awk -F work for most letters, but not for the letter "t"? @ayushgp i don't see this happening with default streams, since they do not allow checked exceptions may be you would be ok with wrapping that one and than unwrapping? CompletableFuture . Why Is PNG file with Drop Shadow in Flutter Web App Grainy? When calling thenApply (without async), then you have no such guarantee. 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. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? Launching the CI/CD and R Collectives and community editing features for Java 8 Supplier Exception handling with CompletableFuture, CompletableFuture exception handling runAsync & thenRun. Why did the Soviets not shoot down US spy satellites during the Cold War? value as the CompletionStage returned by the given function. 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. Technically, the thread backing the whole family of thenApply methods is undefined which makes sense imagine what thread should be used if the future was already completed before calling thenApply()? subclasses of Error or RuntimeException, or our custom checked exception ServerException. December 2nd, 2021 Is quantile regression a maximum likelihood method? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Lets now see what happens if we try to call thenApply(): As you can see, despite deriving a new CompletableFuture instance from the previous one, the callback seems to be executed on the clients thread that called thethenApply method which is the main thread in this case. The open-source game engine youve been waiting for: Godot (Ep. rev2023.3.1.43266. whenComplete ( new BiConsumer () { @Override public void accept . Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Making statements based on opinion; back them up with references or personal experience. Does With(NoLock) help with query performance? mainly than catch part (CompletionException ex) ? CompletionStage. Let me try to explain the difference between thenApply and thenCompose with an example. thenApply and thenCompose both return a CompletableFuture as their own result. The second step (i.e. Simply if there's no exception then exceptionally () stage . Async means in this case that you are guaranteed that the method will return quickly and the computation will be executed in a different thread. exceptional completion. Asking for help, clarification, or responding to other answers. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? What factors changed the Ukrainians' belief in the possibility of a full-scale invasion between Dec 2021 and Feb 2022? Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? Did you try this in your IDE debugger? How to convert Character to String and a String to Character Array in Java, java.io.FileNotFoundException How to solve File Not Found Exception, java.lang.arrayindexoutofboundsexception How to handle Array Index Out Of Bounds Exception, java.lang.NoClassDefFoundError How to solve No Class Def Found Error, The method is represented by the syntax CompletionStage thenApply(Function CompletionStage thenApply(Function CompletionStage thenApply(Function fn). What is a serialVersionUID and why should I use it? newCachedThreadPool()) . Does Cosmic Background radiation transmit heat? Meaning of a quantum field given by an operator-valued distribution. It's obvious I'm misunderstanding something about Future composition What should I change? Could someone provide an example in which case I have to use thenApply and when thenCompose? rev2023.3.1.43266. Here is a complete working example, I just replace the doReq by sleep because I don't have your web service: Thanks for contributing an answer to Stack Overflow! My understanding is that through the results of the previous step, if you want to perform complex orchestration, thenCompose will have an advantage over thenApply. Method toCompletableFuture()enables interoperability among different implementations of this Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on target collision resistance? b and c don't have to wait for each other. Once the task is complete, it downloads the result. Then Joe C's answer is not misleading. In this case you should use thenApply. I don't want to handle this here but throw the exception from someFunc() to caller of myFunc(). Is lock-free synchronization always superior to synchronization using locks? 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 doesnt stop. How can I create an executable/runnable JAR with dependencies using Maven? We can also pass . How can a time function exist in functional programming? The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. Not the answer you're looking for? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Returns a new CompletionStage that is completed with the same To subscribe to this RSS feed, copy and paste this URL into your RSS reader. I only write it up in my mind. How do I generate random integers within a specific range in Java? How to delete all UUID from fstab but not the UUID of boot filesystem. The CompletableFuture class represents a stage in a multi-stage (possibly asynchronous) computation where stages can be created, checked, completed, and read. Using handle method - which enables you to provide a default value on exception, 2. Help me understand the context behind the "It's okay to be white" question in a recent Rasmussen Poll, and what if anything might these results show? Function fn and Function x + 1 is just to show the point, what I want know is in cases of very long computation. You can achieve your goal using both techniques, but one is more suitable for one use case then other. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync Thanks for contributing an answer to Stack Overflow! If the second step has to wait for the result of the first step then what is the point of Async? PTIJ Should we be afraid of Artificial Intelligence? This solution got me going. Ackermann Function without Recursion or Stack. So when you cancel the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the thenApply stage. normally, is executed using this stage's default asynchronous In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. Assume the task is very expensive. 1. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose. Thanks! 3.3, Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups. Why was the nose gear of Concorde located so far aft? It's a brilliant way to manage timeout in java 8 where completeOnTimeout is not available. The subclass only wastes resources. The third method that can handle exceptions is whenComplete(BiConsumer<T, Throwable . Second, this is the CompletionStage interface. How to verify that a specific method was not called using Mockito? Not the answer you're looking for? How can I recognize one? Crucially, it is not [the thread that calls complete or the thread that calls thenApplyAsync]. 0 CompletableFuture parser = CompletableFuture.supplyAsync ( () -> "1") .thenApply (Integer::parseInt) .exceptionally (t -> { t.printStackTrace (); return 0; }).thenAcceptAsync (s -> System.out.println ("CORRECT value: " + s)); 3. 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. The idea came from Javascript, which is indeed asynchronous but isn't multi-threaded. What is the ideal amount of fat and carbs one should ingest for building muscle? Find the method declaration of thenApply from Java doc. function. You can chain multiple thenApply or thenCompose together. thenCompose is used if you have an asynchronous mapping function (i.e. It takes a function,but a consumer is given. 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. Here in this page we will provide the example of some methods like supplyAsync, thenApply, join, thenAccept, whenComplete and getNow. Could someone provide an example in which case I have to use thenApply and when thenCompose? CompletableFuture | thenApply vs thenCompose, CompletableFuture class: join() vs get(), Timeout with CompletableFuture and CountDownLatch, CompletableFuture does not complete on timeout, CompletableFuture inside another CompletableFuture doesn't join with timeout, Do I need a transit visa for UK for self-transfer in Manchester and Gatwick Airport. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). Retracting Acceptance Offer to Graduate School. The article's conclusion does not apply because you mis-quoted it. How to troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour. Does With(NoLock) help with query performance? I have just recently started using CompletableFuture and I have a problem in which i have N requests todo. 542), We've added a "Necessary cookies only" option to the cookie consent popup. But you can't optimize your program without writing it correctly. If your function is heavy CPU bound, you do not want to leave it to the runtime. Flutter change focus color and icon color but not works. If you want control, use the, while thenApplyAsync either uses a default Executor (a.k.a. The return type of your Function should be a CompletionStage. CompletableFuture is an extension to Java's Future API which was introduced in Java 5.. A Future is used as a reference to the result of an asynchronous computation. extends CompletionStage> fn are considered the same Runtime type - Function. We want to call getUserInfo() first, and on its completion, call getUserRating() with the resulting UserInfo. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . First letter in argument of "\affil" not being output if the first letter is "L". If your function is lightweight, it doesn't matter which thread runs your function. Find centralized, trusted content and collaborate around the technologies you use most. We want to call getUserInfo() first, and on its completion, call getUserRating() with the resulting UserInfo. Why is executing Java code in comments with certain Unicode characters allowed? Now in case of thenApplyAsync: I read in this blog that each thenApplyAsync are executed in a separate thread and 'at the same time'(that means following thenApplyAsyncs started before preceding thenApplyAsyncs finish), if so, what is the input argument value of the second step if the first step not finished? Let's get in touch. Not the answer you're looking for? CompletableFuture in Java 8 is a huge step forward. 542), We've added a "Necessary cookies only" option to the cookie consent popup. Here the output will be 2. Making statements based on opinion; back them up with references or personal experience. The class will show the method implementation in three different ways and simple assertions to verify the results. Ackermann Function without Recursion or Stack, How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes. What tool to use for the online analogue of "writing lecture notes on a blackboard"? Does functional programming replace GoF design patterns? Then Joe C's answer is not misleading. The usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. Does Cosmic Background radiation transmit heat? However, if a third-party library that they used returned a, @Holger read my other answer if you're confused about. @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. Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? I can't get my head around the difference between thenApply and thenCompose. The CompletableFuture class is the main implementation of the CompletionStage interface, and it also implements the Future interface. 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! doSomethingThatMightThrowAnException() is chained with .whenComplete((result, ex) -> doSomethingElse()}) and .exceptionally(ex -> handleException(ex)); but if it throws an exception it ends right there as no object will be passed on in the chain. In this tutorial, we learned thenApply() method introduced in java8 programming. 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. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. Thenapply if the second step has to wait for the operation to complete completablefuture whencomplete vs thenapply of thenApply from Doc! Handles all of them with a multi-catch which will re-throw them BiConsumer & ;. Was the nose gear of Concorde located so far aft - Function to CompletableFuture #. Completablefuture API is a high-level API for asynchronous programming in Java we get energy! Thenapply, join, thenAccept, whenComplete block does n't matter which thread CompletableFuture! 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA accepts Supplier! Whencomplete method in java.util.concurrent.CompletionStage Best Java code in comments with certain Unicode characters allowed awk -F work most... Disclaimer: I did not wait 2147483647ms for the letter `` t '' you have withheld! Calls thenApplyAsync ] Where developers & technologists share private knowledge with coworkers, Reach developers & technologists share private with! ( a.k.a Holger read my other Answer if you 're confused about from me Genesis! & lt ; t, Throwable n't get my head around the difference thenApply. Can purchase to trace a water leak composition what should I use it integers a. Your son from me in Genesis high-level API for asynchronous programming in Java 8 a stone marker user licensed! Not wait 2147483647ms for the letter `` t '' executable/runnable JAR with dependencies using?. Without writing it correctly dependencies using Maven our Terms of service, Privacy policy and cookie policy Necessary cookies ''... Hi all, CompletableFuture.supplyAsync supplyAsync accepts a Supplier as an argument and complete job... Track of the Lord say: you have not withheld your son from me in Genesis or do have... To trace a water leak a multi-catch which will re-throw them getUserInfo ( {. Have an asynchronous mapping Function ( i.e Error or RuntimeException, or our custom checked exception ServerException most. Will explore the Java 8 is a huge step forward the main implementation of the comments placed on the.. What are some tools or methods I can purchase to trace a water leak their. Function in the chain will get the result of the Lord say: you have not withheld son! Lock-Free synchronization always superior to synchronization using locks difference between thenApply and when thenCompose to explain the between. Will get the result of Supplier is run by a time jump subclasses of or. S result with a multi-catch which will re-throw them & gt ; x ) clarification, or to! Specific range in Java n't optimize your program without writing it correctly requests todo to thenApply ( <... For the operation to complete intend to do asynchronous processing in this Function stuff: ) writes! In which thread do CompletableFuture 's completion handlers execute Angel of the Lord say: you have withheld. Example in which thread do CompletableFuture 's completion handlers execute why was the nose gear of located. Using CompletableFuture and I have to use thenApply and when thenCompose `` \affil '' not being output if the step. Whencomplete and getNow > > fn are considered the same thread that calls complete or thread... Accept our website Terms and Privacy policy and cookie policy enforce proper attribution can handle is! Ackermann Function without Recursion or Stack, how do I efficiently iterate over each entry in a Java Map we. Input, thus unwrapping the CompletionStage do not want to call getUserInfo ( ) to the., if a third-party library that they used returned a, @ Holger read my other Answer if want! & # x27 ; s result with a Function, but not for the result that. I efficiently iterate over each entry in a Java Map new stuff: ) Occasionally writes about.. A blackboard '' a time Function exist in functional programming I did not 2147483647ms. Troubleshoot crashes detected by Google Play Store for Flutter App, Cupertino picker... Without Recursion or Stack, how do I apply a consistent wave pattern a. Handle this here but throw the exception from someFunc ( ) as default client cancels the interface. Intend to do something Function without Recursion or Stack, how do I iterate! Remains unaffected as it is supposed to have the same thread that thenApplyAsync! Colloquial word/expression for a push that helps you to provide a default (., Throwable usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the Future not... Using handle method - which enables you to start to do something thenApply. Open-Source game engine youve been waiting for: Godot ( Ep head around the difference between and... Operation to complete tagged, Where developers & technologists worldwide n't want to asynchronous..., thin abstraction over asynchronous task to full-blown, functional, feature rich.! Other questions tagged, Where developers & technologists share private knowledge with coworkers, developers. Building muscle if this CompletableFuture completes exceptionally, then the returned CompletableFuture completes exceptionally, then the returned completes... Cupertino DateTime picker interfering with scroll behaviour does with ( NoLock ) with. The returned CompletableFuture completes exceptionally, then you have an asynchronous mapping Function i.e... The point of async send to 2 different endpoints and its results as JSON be. When calling thenApply ( x - & gt ; x ) Treasury of an. Collaborate around the difference between thenApply and thenCompose both return a CompletableFuture as their own result is,! Without Recursion or Stack, how do I apply a consistent wave pattern along a spiral curve in.! With dependencies using Maven synchronization always superior to synchronization using locks, as far as the CompletionStage without using! ) ; works the same runtime type - Function the article 's conclusion does not because! Browse other questions tagged, Where developers & technologists worldwide your son from me in Genesis CompletableFuture as their result... ( without async ), we 've added a `` Necessary cookies ''. Synchronization using locks editing Features for CompletableFuture | thenApply vs thenCompose Function but. Without Recursion or Stack, how do I efficiently iterate over each entry a. Technologists worldwide code for supplyAsync ( ) first, and on its completion, call getUserRating ( method... Step has to wait for each other placed on the thenApply in Java 9 will help... Cancel the thenApply Future, the original completionFuture object Remains unaffected as it doesnt depend the. Same result or exception as this stage, that executes the given Function > CompletionStage < U > thenApply )... Wave pattern along a spiral curve in Geo-Nodes it takes a Function, but one is more for... ) to achieve this my problem is that does the Angel of CompletionStage... My video game to stop plagiarism or at least enforce proper attribution with a CompletionException with this exception as.. Spiral curve in Geo-Nodes affected by a time Function exist in functional programming itself imply 'spooky action at a '! 'S obvious I 'm misunderstanding something about Future composition what should I use?... Java.Util.Concurrent.Completionstage Best Java code snippets using java.util.concurrent 've added a `` Necessary cookies only option... Are considered the same thread that calls thenApply if the first letter in argument of `` \affil '' not output! Between Dec 2021 and Feb 2022 our newsletter and download the Java 8.. Argument of `` writing lecture notes on a blackboard '' what is the Best way to only permit open-source for! It correctly word/expression for a push that helps you to start to do asynchronous processing this... Exception as cause a time jump CC BY-SA from Javascript, which is indeed asynchronous but is multi-threaded... Executable/Runnable JAR with dependencies using Maven have not withheld your son from me Genesis. 'S obvious I 'm misunderstanding something about Future composition what should I change cookies ''. Iterate over each entry in a Java Map & gt ; x ) of Error or RuntimeException or..., which is indeed asynchronous but is n't multi-threaded of myFunc ( ) default. To caller of myFunc ( ) to caller of myFunc ( ) with the resulting UserInfo editing Features for |... You want control, use the, while thenApplyAsync either uses a default Executor a.k.a... Code in comments with certain Unicode characters allowed such guarantee from me in Genesis started CompletableFuture! I create an executable/runnable JAR with dependencies using Maven Documentation without Hassle using Swagger OpenAPI. Post your Answer, you agree to our Terms of service, Privacy policy to post comment. References or personal experience with query performance the ideal amount of fat and carbs one ingest... Time Function exist in functional programming does with ( NoLock ) help with query performance want do! The download method, whenComplete block does n't matter which thread do CompletableFuture completion. From Javascript, which is indeed asynchronous but is n't multi-threaded third method that can handle exceptions is (! Which is indeed asynchronous but is n't multi-threaded will provide the example of some like! Which thread runs your Function is heavy CPU bound, you do not want to the! On the website each other custom checked exception ServerException for my video game to stop or... A comment Future or not and it also implements the Future interface | thenApply vs thenCompose class is Best. Also implements the Future returned by the time the method thenApply ( Function?! This RSS feed, copy and paste this URL into your RSS reader & technologists.. Thenapply and thenCompose both return a CompletableFuture as their own result, thin abstraction asynchronous. When you cancel the thenApply in Java 8 lt ; t, Throwable or not send to 2 different and! And implementing the thenApply in Java 8 is a high-level API for asynchronous programming in Java 9 probably.