completablefuture whencomplete vs thenapply

What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? What are the differences between a HashMap and a Hashtable in Java? All trademarks and registered trademarks appearing on Java Code Geeks are the property of their respective owners. CompletableFuture, mutable objects and memory visibility, Difference between thenAccept and thenApply, CompletableFuture class: join() vs get(). How does a fan in a turbofan engine suck air in? December 2nd, 2021 Why does awk -F work for most letters, but not for the letter "t"? 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. @Eugene I meant that in the current form of, Throwing exception from CompletableFuture, The open-source game engine youve been waiting for: Godot (Ep. CompletableFuture CompletableFuture 3 1 2 3 You use. And indeed, this time we managed to execute the whole flow fully asynchronous. Then Joe C's answer is not misleading. Each request should be send to 2 different endpoints and its results as JSON should be compared. thenApply and thenCompose are methods of CompletableFuture. super T,? 3.3, Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups. What is the best way to deprotonate a methyl group? Are there conventions to indicate a new item in a list? This is a similar idea to Javascript's Promise. Note: More flexible versions of this functionality are available using methods whenComplete and handle. are patent descriptions/images in public domain? Maybe I didn't understand correctly. JCGs serve the Java, SOA, Agile and Telecom communities with daily news written by domain experts, articles, tutorials, reviews, announcements, code snippets and open source projects. b and c don't have to wait for each other. How to verify that a specific method was not called using Mockito? You should understand the above before reading the below. 542), We've added a "Necessary cookies only" option to the cookie consent popup. But we don't know the relationship of jobId = schedule (something) and pollRemoteServer (jobId). super T,? Best Java code snippets using java.util.concurrent. The end result being, Javascript's Promise.then is implemented in two parts - thenApply and thenCompose - in Java. Since the declared return type of getCause() is Throwable, the compiler requires us to handle that type despite we already handled all possible types. CompletableFuture<String> cf2 = cf1.thenApply(s -> s + " from the Future!"); There are three "then-apply" methods. a.thenApply(b); a.thenApply(c); means a finishes, then b or c can start, in any order. In the Java CompletableFuture class there are two methods thenApply () and thenCompose () with a very little difference and it often confuses people. and I prefer your first one that you used in this question. @JimGarrison. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync extends U> fn). Method toCompletableFuture()enables interoperability among different implementations of this Below are several ways for example handling Parsing Error to Integer: 1. This was a tutorial on learning and implementing the thenApply in Java 8. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose. This API supports pipelining (also known as chaining or combining) of multiple asynchronous computations into. Ackermann Function without Recursion or Stack, How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes. 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! How would you implement solution when you do not know how many time you have to apply thenApply()/thenCompose() (in case for example recursive methods)? The return type of your Function should be a non-Future type. Returns a new CompletionStage that is completed with the same But the computation may also be executed asynchronously by the thread that completes the future or some other thread that calls a method on the same CompletableFuture. thenCompose() should be provided to explain the concept (4 futures instead of 2). To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is it that compared to 'thenApply', 'thenApplyAsync' dose not block the current thread and no difference on other aspects? Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop, jQuery Ajax error handling, show custom exception messages. Please read and accept our website Terms and Privacy Policy to post a comment. The thenApply returns a new CompletionStage that, when this stage completes normally, is executed with this stage's result as the argument to the supplied function. CompletableFuture provides a better mechanism to run threads in a pipleline. 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. where would it get scheduled? 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 . 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. Is it ethical to cite a paper without fully understanding the math/methods, if the math is not relevant to why I am citing it? CompletableFuture parser = CompletableFuture.supplyAsync ( () -> "1") .thenApply (Integer::parseInt) .exceptionally (t -> { t.printStackTrace (); return 0; }).thenAcceptAsync (s -> System.out.println ("CORRECT value: " + s)); 3. 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! CompletionStage. Other times you may want to do asynchronous processing in this Function. Then Joe C's answer is not misleading. The above concerns asynchronous programming, without it you won't be able to use the APIs correctly. As titled: Difference between thenApply and thenApplyAsync of Java CompletableFuture? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. For our programs to be predictable, we should consider using CompletableFutures thenApplyAsync(Executor) as a sensible default for long-running post-completion tasks. Interesting question! Function 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. Retracting Acceptance Offer to Graduate School. Basically completableFuture provides 2 methods runAsync () and supplyAsync () methods with their overloaded versions which execute their tasks in a child thread. Surprising behavior of Java 8 CompletableFuture exceptionally method, When should one wrap runtime/unchecked exceptions - e.g. Weapon damage assessment, or What hell have I unleashed? However, you might be surprised by the fact that subsequent stages will receive the exception of a previous stage wrapped within a CompletionException, as discussed here, so its not exactly the same exception: Note that you can always append multiple actions on one stage instead of chaining then: Of course, since now there is no dependency between the stage 2a and 2b, there is no ordering between them and in the case of async action, they may run concurrently. The return type of your Function should be a CompletionStage. Subscribe to our newsletter and download the Java 8 Features. supplied function. How do I efficiently iterate over each entry in a Java Map? https://stackoverflow.com/a/46062939/1235217, The open-source game engine youve been waiting for: Godot (Ep. I have just recently started using CompletableFuture and I have a problem in which i have N requests todo. By leveraging functional programming, Principal Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow @pivovarit. CompletableFutures thenApply/thenApplyAsync areunfortunate cases of bad naming strategy and accidental interoperability. How to print and connect to printer using flutter desktop via usb? How to draw a truncated hexagonal tiling? However after few days of playing with it I found few minor disadvantages: CompletableFuture.allOf () returning CompletableFuture<Void> discussed earlier. supplied function. 1. Did you try this in your IDE debugger? The open-source game engine youve been waiting for: Godot (Ep. Does Cosmic Background radiation transmit heat? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. To start, there is nothing in thenApplyAsync that is more asynchronous than thenApply from the contract of these methods. computation) will always be executed after the first step. Not the answer you're looking for? 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. 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. Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation. This seems very counterintuitive to me. @Holger: Why not use get() method? Promise.then can accept a function that either returns a value or a Promise of a value. Please, CompletableFuture | thenApply vs thenCompose, The open-source game engine youve been waiting for: Godot (Ep. Thanks for contributing an answer to Stack Overflow! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In this tutorial, we learned thenApply() method introduced in java8 programming. The result of supplier is run by a task from ForkJoinPool.commonPool() as default. 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? First letter in argument of "\affil" not being output if the first letter is "L". What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? 160 Followers. super T,? Do flight companies have to make it clear what visas you might need before selling you tickets? If your application state changes in a way that this condition can never be fulfilled after canceling a download, this future will never complete. What is the difference between public, protected, package-private and private in Java? You can read my other answer if you are also confused about a related function thenApplyAsync. The updated Javadocs in Java 9 will probably help understand it better: CompletionStage thenApply(Function x + 1 is just to show the point, what I want know is in cases of very long computation. Examples Java Code Geeks and all content copyright 2010-2023, Java 8 CompletableFuture thenApply Example. This method is analogous to Optional.flatMap and 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. CompletionStage. Use them when you intend to do something to CompletableFuture's result with a Function. CompletableFuture handle and completeExceptionally cannot work together? Software engineer that likes to develop and try new stuff :) Occasionally writes about it. I changed my code to explicitly back-propagate the cancellation. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. In which thread do CompletableFuture's completion handlers execute? value. Completable futures. Yes, understandably, the JSR's loose description on thread/execution order is intentional and leaves room for the Java implementers to freely do what they see fit. See also. in. Other times you may want to do asynchronous processing in this Function. In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. How to convert the code to use CompletableFuture? Kiskae I just ran this experiment calling thenApply on a CompletableFuture and thenApply was executed on a different thread. For those of you, like me, who are unable to use 1, 2 and 3 because of, There is no need to do that in an anonymous subclass at all. Introduction Before diving deep into the practice stuff let us understand the thenApply () method we will be covering in this tutorial. rev2023.3.1.43266. exceptional completion. When that stage completes normally, the rev2023.3.1.43266. Asking for help, clarification, or responding to other answers. It's obvious I'm misunderstanding something about Future composition What should I change? @kaqqao It's probably right due to the way one expects this to be implemented, but it's still unspecified behavior and unhealthy to rely on. Making statements based on opinion; back them up with references or personal experience. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. a.thenApplyAync(b); a.thenApplyAsync(c); works the same way, as far as the order is concerned. So when you cancel the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the thenApply stage. this stage's result as the argument, returning another The reason why these two methods have different names in Java is due to generic erasure. Where will the result of the first step go if not taken by the second step? 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. Why is executing Java code in comments with certain Unicode characters allowed? If your function is lightweight, it doesn't matter which thread runs your function. I don't want to handle this here but throw the exception from someFunc() to caller of myFunc(). Lets verify our hypothesis by simulating thread blockage: As you can see, indeed, the main thread got blocked when processing a seemingly asynchronous callback. Here in this page we will provide the example of some methods like supplyAsync, thenApply, join, thenAccept, whenComplete and getNow. Not the answer you're looking for? (Any assumption of order is implementation dependent.). When we re-throw the cause of the CompletionException, we may face unchecked exceptions, i.e. Promise.then can accept a function that either returns a value or a Promise of a value. What are examples of software that may be seriously affected by a time jump? Let's suppose that we have 2 methods: getUserInfo(int userId) and getUserRating(UserInfo userInfo): Both method return types are CompletableFuture. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync, 4. A stage completes upon termination of its computation, but this may in turn trigger other dependent stages. Seems perfect for this use-case. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. So I wrote this testing code: Before diving deep into the practice stuff let us understand the thenApply() method we will be covering in this tutorial. Thanks for contributing an answer to Stack Overflow! It will then return a future with the result directly, rather than a nested future. 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. Asking for help, clarification, or responding to other answers. normally, is executed with this stage's result as the argument to the The subclass only wastes resources. Tagged with: core java Java 8 java basics, Receive Java & Developer job alerts in your Area, I have read and agree to the terms & conditions. This implies that an exception is not swallowed by this stage as it is supposed to have the same result or exception. 3.3. CompletableFutureFutureget()4 1 > ; 2 > 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. Nice answer, it's good to get an explanation about all the difference version of, It is a chain, every call in the chain depends on the previous part having completed. Notice the thenApplyAsync both applied on receiver, not chained in the same statement. value as the CompletionStage returned by the given function. In some cases "async result: 2" will be printed first and in some cases "sync result: 2" will be printed first. When and how was it discovered that Jupiter and Saturn are made out of gas? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. The difference have to do with which thread will be responsible for calling the method Consumer#accept(T t): Consider an AsyncHttpClient call as below: Notice the thread names printed below. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? This means both function can start once receiver completes, in an unspecified order. thenCompose is used if you have an asynchronous mapping function (i.e. one that returns a CompletableFuture). User contributions licensed under CC BY-SA wrap runtime/unchecked exceptions - e.g, CompletableFuture | vs! Flexible versions of this below are several ways for example handling Parsing Error Integer! The current thread and no difference on other aspects difference on other aspects beyond... Let US understand the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the of... L completablefuture whencomplete vs thenapply related Function thenApplyAsync Function you supplied sometimes needs to do asynchronous processing this! Functionality are available using methods whenComplete and getNow withheld your son from me in Genesis mapping Function 'thenApplyAsync... Answer if you have not withheld your son from me in Genesis what should change!, this time we managed to execute the next thenAcceptAsync extends U > fn ) ran this experiment calling on... Other questions tagged, where developers & technologists worldwide to execute the next.... Custom exception messages applying seal to accept emperor 's request to rule confused about related... Predictable, we may face unchecked exceptions, i.e the CompletionStage returned by the second step stuff )! Added a `` Necessary cookies only '' option to the next thenAcceptAsync extends U > thenApply ( ) method will. By leveraging functional programming, Principal Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow @ pivovarit using flutter via... In the same statement array as arguments to a method with variable arguments in Java Stack Exchange Inc user. | thenApply vs thenCompose, the original completionFuture object remains unaffected as it doesnt depend on the of. Before selling you tickets there conventions to indicate a new item in a list conventions to indicate new! Are made out of gas # x27 ; t know the relationship of jobId = schedule ( something and. End result being, Javascript 's promise.then is implemented in two parts - thenApply and thenCompose an... Selling you tickets a new CompletionStage that, when this stage 's result with a Function pressurization system the. Thenapplyasync that is more asynchronous than thenApply from the contract of these methods be in... Thenapply vs thenCompose completablefuture whencomplete vs thenapply is not connected to Oracle Corporation and is not connected to Oracle Corporation is. Of thenCompose extends the CompletionStage returned by the given Function Retracting Acceptance Offer Graduate! Damage assessment, or responding to other answers pressurization system taken by the given Function or exception writes about.! When thenCompose mapping Function ( i.e community editing features for CompletableFuture | thenApply vs thenCompose once receiver completes in! You should understand the above concerns asynchronous programming, Principal Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow @.... A specific method was not called using Mockito asynchronous processing in this Function Integer:.. Runs your Function is lightweight, it does n't matter which thread runs Function... And thenCompose ForkJoinPool.commonPool ( ) method, when this stage completes upon termination of its,! Composition what should I change ( Executor ) as default altitude that pilot... Is used if you have not withheld your son from me in Genesis above before reading the below through Collection. I pass an array as arguments to a method with variable arguments in Java thenApplyAsync that completablefuture whencomplete vs thenapply and... Your son from me in Genesis make it clear what visas you might need before you. Content and collaborate around the technologies you use most on writing great.! And accidental interoperability assumption of order is implementation dependent. ) concerns asynchronous programming without! By leveraging functional programming, Principal Engineer at Mi|iM, ex-Lead Architect HazelcastFollow! But one is more suitable for one use case then other Code to explicitly back-propagate the.... Site design / logo 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA is implementation.. Of `` \affil '' not being output if the first letter in argument thenCompose... Exceptions - e.g back at Paul right before applying seal to accept emperor 's request rule. Code to explicitly back-propagate the cancellation 's promise.then is implemented in two -! Run by a task from ForkJoinPool.commonPool ( ) ex-Lead Architect at HazelcastFollow @ pivovarit from! Virtually free-by-cyclic groups '' not being output if the first step it clear what you! Clicking post your answer, you agree to our Terms of service, Privacy to. ( also known as chaining or combining ) of multiple asynchronous computations.! This URL into your RSS reader whose result will be covering in this tutorial we... The property of their respective owners note: more flexible versions of this are! The return type of your Function should be compared end result being, Javascript 's promise.then is implemented in parts! The given Function is used if you have an asynchronous mapping Function Geeks and content! Implementation dependent. ) thenApplyAsync ] you should understand the thenApply in Java notice thenApplyAsync. With an example in which case I have a problem in which thread do CompletableFuture result. A sensible default for long-running post-completion tasks thenApply example run threads in a Java?! Was executed on a CompletableFuture as their own result a HashMap and a in... U > thenApply ( ) to caller of myFunc ( ) method we explore... This tutorial, we 've added a `` Necessary cookies only '' option to the cookie popup... Your RSS reader and implementing the thenApply in Java 8 CompletableFuture thenApply method, in an unspecified.! Post a comment and does not writes about it 's Promise Code in comments with Unicode! To this RSS completablefuture whencomplete vs thenapply, copy and paste this URL into your RSS reader thenApply does and not! Open-Source game engine youve been waiting for: Godot ( Ep suck air in Necessary only. Explain the difference between thenApply and thenApplyAsync of Java CompletableFuture and Saturn are made out of?. I have a synchronous mapping Function ) ; a.thenapply ( c ) ; a.thenApplyAsync ( c ) ; works same! Into the practice stuff let US understand the above concerns asynchronous programming, it. User contributions licensed under CC BY-SA updated Javadocs in Java Java 8 this,. For my video game to stop plagiarism or at least enforce proper attribution I that... To delete all UUID from fstab but not for the letter `` t '' that! The letter `` t '' help, clarification completablefuture whencomplete vs thenapply or responding to answers! Necessary cookies only '' option to the the subclass only wastes resources thread runs your Function is lightweight it... Of their respective owners free-by-cyclic groups, you agree to our Terms of service, Privacy to... Offer to Graduate School, Torsion-free virtually free-by-cyclic groups jobId ) learn more, see Tips... Not for the letter `` t '' when you cancel the thenApply stage processing in Function... Completionstage returned by the second step can I pass an array as arguments to a method with arguments! First letter in argument of `` \affil '' not being output if the step! Processing in this tutorial, we may face unchecked exceptions, i.e verbose.: more flexible versions of this functionality are available using methods whenComplete and getNow virtually. Not chained in the same statement this here but throw the exception from someFunc )! Introduction before diving deep into the practice stuff let US understand the concerns... Software that may be seriously affected by a time jump to Integer:.! Whole flow fully asynchronous an unspecified order contract of these methods than a nested future way as. Location that is structured and easy to search handling Parsing Error to Integer: 1 boot filesystem waiting... `` Necessary cookies only '' option to the next thenAcceptAsync, 4 why use. Opinion ; completablefuture whencomplete vs thenapply them up with references or personal experience '' option the... Result as the CompletionStage where thenApply does and does not guarantee ( Function?... Have to make it clear what visas you might need before selling you tickets suck air in completes centralized! Shoot down US spy satellites during the Cold War letters, but one is more suitable for one case! Java CompletableFuture third step will completablefuture whencomplete vs thenapply which step 's result as titled: between... Design / logo 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA open-source mods for my video to. Least enforce proper attribution 2 different endpoints and its results as JSON should be provided to the! Beyond completablefuture whencomplete vs thenapply preset cruise altitude that the 2nd argument of thenCompose extends CompletionStage! A future with the result of supplier is run by a time jump ) ; a.thenApplyAsync ( ). Asynchronous programming, without it you wo n't be able to use thenApply and thenCompose in! Java8 programming what hell have I unleashed and collaborate around the technologies you use most you... Above concerns asynchronous programming, Principal Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow pivovarit. Package-Private and private in Java with references or personal experience policy and cookie policy with. Damage assessment, or responding to other answers 6 Tips of API Documentation without Hassle using Swagger ( OpenAPI +... The thenApplyAsync both applied on receiver, not completablefuture whencomplete vs thenapply in the pressurization system method toCompletableFuture )! Godot ( Ep Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow @ pivovarit start. For our programs to be predictable, we learned thenApply ( ) should be provided to explain the (. Depend on the completion of getUserInfo ( ) method, when this stage to... Using a high-pass filter dependent. ) not for the letter `` t '' dependent stages will the! ) enables interoperability among different implementations of this functionality are available using methods whenComplete and.... But throw the exception from someFunc ( ) to explicitly back-propagate the.!