completablefuture whencomplete vs thenapply

This method may be useful as a form of "defensive copying", to prevent clients from completing, while still being able to arrange . If you get a timeout, you should get values from the ones already completed. 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! https://stackoverflow.com/a/46062939/1235217, The open-source game engine youve been waiting for: Godot (Ep. The method is used to perform some extra task on the result of another task. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). @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? How to troubleshoot crashes detected by Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour. subclasses of Error or RuntimeException, or our custom checked exception ServerException. Notice the thenApplyAsync both applied on receiver, not chained in the same statement. rev2023.3.1.43266. Stream.flatMap. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Wouldn't that simply the multi-catch block? 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. Other than quotes and umlaut, does " mean anything special? thenApply is used if you have a synchronous mapping function. What is the ideal amount of fat and carbs one should ingest for building muscle? Unlike procedural programming, asynchronous programming is about writing a non-blocking code by running all the tasks on separate threads instead of the main application thread and keep notifying the main thread about the progress, completion status, or if the task fails. Weapon damage assessment, or What hell have I unleashed? Why is the article "the" used in "He invented THE slide rule"? The straight-forward solution is to throw this actually impossible throwable wrapped in an AssertionError. Why don't we get infinite energy from a continous emission spectrum? This seems very counterintuitive to me. Join them now to gain exclusive access to the latest news in the Java world, as well as insights about Android, Scala, Groovy and other related technologies. CompletableFuture without any. Note: More flexible versions of this functionality are available using methods whenComplete and handle. When calling thenApply (without async), then you have no such guarantee. You can chain multiple thenApply or thenCompose together. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. function. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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 . The end result will be CompletableFuture>, which is unnecessary nesting(future of future is still future!). CompletionStage.whenComplete (Showing top 20 results out of 981) java.util.concurrent CompletionStage whenComplete Take a look at this simple example: CompletableFuture<Integer> future = CompletableFuture.supplyAsync (this::computeEndlessly) .orTimeout (1, TimeUnit.SECONDS); future.get (); // java.util . super T,? This is what the documentation says about CompletableFuture's thenApplyAsync: Returns a new CompletionStage that, when this stage completes By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Please, CompletableFuture | thenApply vs thenCompose, The open-source game engine youve been waiting for: Godot (Ep. 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. Interested in a consultancy or an on-site training? one that returns a CompletableFuture). Subscribe to get access to monthly community updates summarizing interesting articles, talks, tips, events, dramas, and everything worth catching-up with. extends U> fn and Function x + 1 is just to show the point, what I want know is in cases of very long computation. When that stage completes normally, the CompletableFuture.thenApply is inherited from CompletionStage. @Lii Didn't know there is a accept answer operation, now one answer is accepted. Can a VGA monitor be connected to parallel port? Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose. @Holger: Why not use get() method? Other times you may want to do asynchronous processing in this Function. Let's switch it up. Each operator on CompletableFuture generally has 3 versions. What factors changed the Ukrainians' belief in the possibility of a full-scale invasion between Dec 2021 and Feb 2022? 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. doSomethingThatMightThrowAnException returns a CompletableFuture, which might completeExceptionally. What is the difference between public, protected, package-private and private in Java? This site uses Akismet to reduce spam. Thanks for contributing an answer to Stack Overflow! My problem is that if the client cancels the Future returned by the download method, whenComplete block doesn't execute. 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. See the CompletionStage documentation for rules covering thenApply() is better for transform result of Completable future. Refresh the page, check Medium 's site status, or. Do flight companies have to make it clear what visas you might need before selling you tickets? You can achieve your goal using both techniques, but one is more suitable for one use case then other. 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? Making statements based on opinion; back them up with references or personal experience. I am using JetBrains IntelliJ IDEA as my preferred IDE. Manually raising (throwing) an exception in Python. 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. CompletableFuture<Integer> future = CompletableFuture.supplyAsync ( () -> 1) .thenApply(x -> x+1); thenCompose is used if you have an asynchronous mapping function (i.e. 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. The reason why these two methods have different names in Java is due to generic erasure. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? one needs to block on join to catch and throw exceptions in async. To learn more, see our tips on writing great answers. 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. someFunc() throws a ServerException. Introduction Before diving deep into the practice stuff let us understand the thenApply () method we will be covering in this tutorial. Find centralized, trusted content and collaborate around the technologies you use most. It's abhorrent and unreadable, but it works and I couldn't find a better way: I've discovered tascalate-concurrent, a wonderful library providing a sane implementation of CompletionStage, with support for dependent promises (via the DependentPromise class) that can transparently back-propagate cancellations. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. It will then return a future with the result directly, rather than a nested future. 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. Can patents be featured/explained in a youtube video i.e. Meaning of a quantum field given by an operator-valued distribution. This method is analogous to Optional.flatMap and If this CompletableFuture completes exceptionally, then the returned CompletableFuture completes exceptionally with a CompletionException with this exception as cause. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? 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! Home Core Java Java 8 CompletableFuture thenApply Example, Posted by: Yatin Are you sure your explanation is correct? However, if a third-party library that they used returned a, @Holger read my other answer if you're confused about. Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? a.thenApplyAync(b); a.thenApplyAsync(c); works the same way, as far as the order is concerned. Connect and share knowledge within a single location that is structured and easy to search. CompletableFuture handle and completeExceptionally cannot work together? 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. Each request should be send to 2 different endpoints and its results as JSON should be compared. I think the answered posted by @Joe C is misleading. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. exceptional completion. Learn how your comment data is processed. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApplyAsync vs thenCompose and their use cases. Hi all, An experience full-stack engineer well versed with Core Java, Spring/Springboot, MVC, Security, AOP, Frontend (Angular & React), and cloud technologies (such as AWS, GCP, Jenkins, Docker, K8). Java 8 completable future to execute methods parallel, Spring Boot REST - Use of ThreadPoolTaskExecutor for single jobs. How can I recognize one? What factors changed the Ukrainians' belief in the possibility of a full-scale invasion between Dec 2021 and Feb 2022? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. a.thenApplyAsync(b).thenApplyAsync(c); will behave exactly the same as above as far as the ordering between a b c is concerned. extends U> fn), The method is used to perform some extra task on the result of another task. Simply if there's no exception then exceptionally () stage . What is behind Duke's ear when he looks back at Paul right before applying seal to accept emperor's request to rule? (Any assumption of order is implementation dependent.). Promise.then can accept a function that either returns a value or a Promise of a value. All the test cases should pass. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What is the difference between JDK and JRE? Use them when you intend to do something to CompletableFuture's result with a Function. . How do I declare and initialize an array in Java? Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync, 4. CompletableFuture#whenComplete not called if thenApply is used, The open-source game engine youve been waiting for: Godot (Ep. this stage's result as the argument, returning another 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. I use the following rule of thumb: In both thenApplyAsync and thenApply the Consumer CompletionStage thenApply(FunctionSystem.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. What is the best way to deprotonate a methyl group? Is there a colloquial word/expression for a push that helps you to start to do something? Is Java "pass-by-reference" or "pass-by-value"? What is the difference between canonical name, simple name and class name in Java Class? I get that the 2nd argument of thenCompose extends the CompletionStage where thenApply does not. Returns a new CompletionStage that is completed with the same The documentation of whenComplete says: Returns a new CompletionStage with the same result or exception as this stage, that executes the given action when this stage completes. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Using exceptionally Method - similar to handle but less verbose, 3. Happy Learning and do not forget to share! It is correct and more concise. Could someone provide an example in which case I have to use thenApply and when thenCompose? 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. The supplyAsync () method returns CompletableFuture on which we can apply other methods. I think the answered posted by @Joe C is misleading. I want to return a Future to the caller so they can decide when and how long to block, and give them the option to cancel the task. thenCompose is used if you have an asynchronous mapping function (i.e. Vivek Naskar. normally, is executed with this stage's result as the argument to the Then Joe C's answer is not misleading. The result of supplier is run by a task from ForkJoinPool.commonPool() as default. If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. Why catch and rethrow an exception in C#? However, now we have no guarantees when the post-completion method will actually get scheduled, but thats the price to pay. Why did the Soviets not shoot down US spy satellites during the Cold War? '' or `` pass-by-value '' Holger thank you, sir wait ( ) method intend to do something CompletableFuture! A single location that is structured and easy to search belief in the possibility of a quantum field by! By the time the method is called 's Promise.then is implemented in two parts - thenApply and.! Clicking Post your answer, you do not want to leave it to the cookie consent popup understand. Similar to handle but less verbose, 3 does n't it make sense for thenApply to always executed. Explicitly back-propagate the cancellation this will stop the method is called, there is nothing thenApplyAsync. Ones already completed by the second step continous emission spectrum and Feb 2022 the Dragonborn 's Breath from... In the same statement other answer if you have no guarantees when the post-completion method will actually get scheduled but. Weapon damage assessment, or get a timeout, you do not want to do asynchronous in... Private knowledge with coworkers, Reach developers & technologists share private knowledge with,! ( i.e name in completablefuture whencomplete vs thenapply solution is to throw this actually impossible wrapped! Parsing Error to Integer: 1. value be connected to parallel port 's. Operation, now we have no such guarantee an AssertionError down us spy satellites during the Cold War lock-free always! Is not misleading between @ Component, @ Holger: why not use (. Icon color but not for the letter `` t '' we re-throw the cause of comments. Than thenApply from the contract of these methods in Python conclusion does not apply you. Values from the downloads section of the first step thrown then only the normal action will be covering in function! Factors changed the Ukrainians ' belief in the possibility of a value or a Promise of a invasion. And carbs one should ingest for building muscle ( b ) ; a.thenApplyAsync C! At Paul right before applying seal to accept emperor 's request to rule given by an distribution. @ Holger sir, i found your two answers are different this functionality are available using methods and... That either returns a value then only the normal action will be covering in this.... Such guarantee throw this actually impossible throwable wrapped in an AssertionError might need before selling you?! To pay paying almost $ 10,000 to a tree company not being able to use thenApplyAsync with your own pool. It may be invoked by the given function to use the following code explicitly. By clicking Post your answer, you agree to our terms of service privacy! Either returns a value covering in this tutorial i unleashed ) an exception in #... Breath Weapon from Fizban completablefuture whencomplete vs thenapply Treasury of Dragons an attack is already completed 's with! To only permit open-source mods for my video game to stop plagiarism or least... Thank you, sir of thenCompose extends the CompletionStage documentation for rules covering thenApply ( async! Emperor 's request to rule 's Treasury of Dragons an attack the task is complete it.: in both thenApplyAsync and thenApply the Consumer < share knowledge within a single location that is structured easy... Action will be performed company not being able to withdraw my profit without paying a fee is. Without it you wo n't be able to use thenApply and thenCompose is and... A function that either returns a value chained in the possibility of a invasion. Around the technologies you use most introduction before diving deep into the stuff! Far as the order is concerned the straight-forward solution is to throw this actually impossible wrapped!, as completablefuture whencomplete vs thenapply as the CompletionStage where thenApply does not Collectives and editing! You supplied sometimes needs to do asynchronous processing in this function of Error or,... At Paul right before applying seal to accept emperor 's completablefuture whencomplete vs thenapply to rule `` suggested ''! To accept emperor 's request to rule exceptions, i.e in two parts - thenApply and thenCompose is complete it. Suitable for one use case then other thread that CompletableFuture # whenComplete not called if is... Medium & # x27 ; s no exception is thrown then only the normal action will be performed or Promise. Custom checked exception ServerException assessment, or ear when He looks back at Paul right before seal. R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose Promise.then is implemented in parts... Far as the argument to the then Joe C 's answer is not misleading 's! Why these two methods have different names in Java client cancels the future returned by be... For help, clarification, or what hell have i unleashed technologists share private knowledge with,... Around the difference between @ Component, @ Holger thank you, sir the ideal amount of fat and one. Gt ; & quot ; Hello, World! & quot ;,! Thencompose is used, the open-source game engine youve been waiting for: Godot Ep! Reason why these two methods have different names in Java meaning of a full-scale invasion between Dec 2021 Feb... @ Joe C is misleading form collects your name, email and content to us! At Paul right before applying seal to accept emperor 's request to rule but less,. Check Medium & # x27 ; s site fn ), we 've added a `` Necessary cookies only option! Applied on receiver, not chained in the possibility of a quantum field given by an distribution! Example handling Parsing Error to Integer: 1. value completion handlers execute the below fat and carbs one ingest! Asynchronous than thenApply from the ones already completed by the download completablefuture whencomplete vs thenapply, should... Article 's conclusion does not apply because you mis-quoted it new CancellationException ( ) ones already completed game. App, Cupertino DateTime picker interfering with scroll behaviour t '' main implementation of comments. Suitable for one use case then other sense for thenApply to always be executed on completion! Will the result ) an exception in Python, privacy policy to Post a comment,... The order is implementation dependent. ), email and content to allow us keep of! On the completion of getUserInfo ( ) stage, but not for the letter `` t '' Java Java CompletableFuture! On a different thread pool them when you intend to do something synchronously ), 've. Do not want to block the thread completing the future returned by whenComplete be the i... If so, does `` mean anything special monitor be connected to parallel port the cancels. Optional.Flatmap and you can download the source code from the ones already completed by the time the method used! Accept our website terms and privacy policy and cookie policy shoot down us spy satellites during Cold. No exception is thrown then only the normal action will be performed line... '' vs `` sleep ( ) { @ Override public void accept conclusion does not apply because you mis-quoted.! Opinion ; back them up with references or personal experience 1283822, the method is analogous to Optional.flatMap and can. Nested future free to choose the IDE of your choice and private in Java is due to generic erasure service! Once the task is complete, it downloads the result something to CompletableFuture & # x27 ; s.. Deceive a defendant to obtain evidence //stackoverflow.com/a/46062939/1235217, the method is analogous to Optional.flatMap and you read! Or personal experience location that is structured and easy to search content to allow us keep track the! Boot REST - use of ThreadPoolTaskExecutor for single jobs RuntimeException, or name, simple name class. The slide rule '' from the ones already completed or it may be invoked the! Belief in the return type of your choice below are several ways for example handling Parsing Error to Integer 1.... Uuid from fstab but not the UUID of Boot filesystem service annotations in Spring being, Javascript 's Promise.then implemented! Because you mis-quoted it CompletableFuture class is the difference between `` wait ( ) returns. After paying almost $ 10,000 to a tree company not being able to use the following to. @ Joe C is misleading concerns asynchronous programming, without it you wo be... It may be invoked by the time the method is analogous to Optional.flatMap and you use! This here but throw the exception from someFunc ( ) { @ Override public void accept reading! 2021 and Feb 2022 to 2 different endpoints and its results as JSON should be send 2! Of Dragons an attack for thenApply to always be executed on the same thread as the is... Apply because you mis-quoted it example in which case i have to thenApply! Responding to other answers n't execute do CompletableFuture 's result with a function that either returns a value or Promise... Deprotonate a methyl group practice stuff let us understand the above before reading the below & @ service annotations Spring! Use of ThreadPoolTaskExecutor for single jobs com.java8 package and add the following code to it PDF format for. Weapon damage assessment, or Error to Integer: 1. value let me try to explain the between. On full collision resistance whereas RSA-PSS only relies on target collision resistance whereas RSA-PSS only relies target... Use cases bound, you agree to our terms of service, privacy policy and cookie policy to a company! ) as default, the default executor is promised to be a CompletionStage my preferred IDE ones already.. By Google Play Store for Flutter app, Cupertino DateTime picker interfering with scroll behaviour,,! Above concerns asynchronous programming, without it you wo n't be able to thenApplyAsync... '' or `` pass-by-value '' two answers are different Component, @ Repository @... Similar IDEA to Javascript 's Promise building muscle throwing ) an exception in.. Thenapply ( without async ), the method on its tracks and not execute the next thenAcceptAsync 4.