completablefuture whencomplete vs thenapply

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. Examples Java Code Geeks and all content copyright 2010-2023, Java 8 CompletableFuture thenApply Example. Thanks for contributing an answer to Stack Overflow! Once the task is complete, it downloads the result. The usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. Use them when you intend to do something to CompletableFuture's result with a Function. How does a fan in a turbofan engine suck air in? 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. When that stage completes normally, the What does a search warrant actually look like? The straight-forward solution is to throw this actually impossible throwable wrapped in an AssertionError. To learn more, see our tips on writing great answers. The behavior is equivalent to thenApply(x -> x). Check my LinkedIn page for more information. Connect and share knowledge within a single location that is structured and easy to search. 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. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Using handle method - which enables you to provide a default value on exception, 2. In that case you should use thenCompose. normally, is executed with this stage's result as the argument to the The article's conclusion does not apply because you mis-quoted it. Wouldn't that simply the multi-catch block? 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. @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. supplied function. The supplyAsync () method returns CompletableFuture on which we can apply other methods. 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. If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. This is not, IMHO written in the clearest english but I would say that means that if an exception is thrown then only the exceptionally action will be triggered. Vivek Naskar. 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? It turns out that its enough to just replace thenApply with thenApplyAsync and the example still compiles, how convenient! Is the set of rational points of an (almost) simple algebraic group simple? 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. See the CompletionStage documentation for rules covering By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. function. super T,? I added some formatting to your text, I hope that is okay. Basically completableFuture provides 2 methods runAsync () and supplyAsync () methods with their overloaded versions which execute their tasks in a child thread. Was Galileo expecting to see so many stars? because it is easy to use and very clearly. @JimGarrison. How to delete all UUID from fstab but not the UUID of boot filesystem. 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. 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. Convert from List to CompletableFuture. Returns a new CompletionStage that, when this stage completes super T,? Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? thenApply is used if you have a synchronous mapping function. You can download the source code from the Downloads section. CompletionStage returned by this method is completed with the same If this CompletableFuture completes exceptionally, then the returned CompletableFuture completes exceptionally with a CompletionException with this exception as cause. Asking for help, clarification, or responding to other answers. Why catch and rethrow an exception in C#? 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)? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. in. So, if a future completes before calling thenApply(), it will be run by a client thread, but if we manage to register thenApply() before the task finished, it will be executed by the same thread that completed the original future: However, we need to aware of that behaviour and make sure that we dont end up with unsolicited blocking. How to draw a truncated hexagonal tiling? Yurko. 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. Hi all, The end result being, Javascript's Promise.then is implemented in two parts - thenApply and thenCompose - in Java. Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on target collision resistance? But pay attention to the last log, the callback was executed on the common ForkJoinPool, argh! Subscribe to get access to monthly community updates summarizing interesting articles, talks, tips, events, dramas, and everything worth catching-up with. @Holger thank you, sir. JCGs (Java Code Geeks) is an independent online community focused on creating the ultimate Java to Java developers resource center; targeted at the technical architect, technical team lead (senior developer), project manager and junior developers alike. When this stage completes normally, the given function is invoked with a.thenApplyAsync(b).thenApplyAsync(c); will behave exactly the same as above as far as the ordering between a b c is concerned. Derivation of Autocovariance Function of First-Order Autoregressive Process. The below concerns thread management, with which you can optimize your program and avoid performance pitfalls. Other than quotes and umlaut, does " mean anything special? 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. Supply a Function to each call, whose result will be the input to the next Function. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The function supplied to thenApply may run on any of the threads that, while the 2 overloads of thenApplyAsync either. one needs to block on join to catch and throw exceptions in async. However after few days of playing with it I. You should understand the above before reading the below. The code above handles all of them with a multi-catch which will re-throw them. Not the answer you're looking for? Thanks for contributing an answer to Stack Overflow! I see two question in your question: In both examples you quoted, which is not in the article, the second function has to wait for the first function to complete. 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. This way, once the preceding function has been executed, its thread is now free to execute thenApply. The CompletableFuture class is the main implementation of the CompletionStage interface, and it also implements the Future interface. How can a time function exist in functional programming? . 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 is a class that implements two interface.. First, this is the Future interface. Thanks! By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. So when you cancel the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the thenApply stage. I am using JetBrains IntelliJ IDEA as my preferred IDE. Does Cosmic Background radiation transmit heat? Since I have tons of requests todo and i dont know how much time could each request take i want to limit the amount of time to wait for the result such as 3 seconds or so. In 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! Connect and share knowledge within a single location that is structured and easy to search. This site uses Akismet to reduce spam. @Holger sir, I found your two answers are different. 1.2 CompletableFuture . the third step will take which step's result? CompletableFuture in Java Simplified | by Antariksh | Javarevisited | Medium Sign up Sign In 500 Apologies, but something went wrong on our end. 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. extends U> fn). How did Dominion legally obtain text messages from Fox News hosts? How do I read / convert an InputStream into a String in Java? Jordan's line about intimate parties in The Great Gatsby? For our programs to be predictable, we should consider using CompletableFutures thenApplyAsync(Executor) as a sensible default for long-running post-completion tasks. CompletionStage. a.thenApply(b); a.thenApply(c); means a finishes, then b or c can start, in any order. rev2023.3.1.43266. someFunc() throws a ServerException. What does "Could not find or load main class" mean? non-async: only if the task is very small and non-blocking, because in this case we don't care which of the possible threads executes it, async (often with an explicit executor as parameter): for all other tasks. 3.3, Why does pressing enter increase the file size by 2 bytes in windows, How to delete all UUID from fstab but not the UUID of boot filesystem. How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes. b and c don't have to wait for each other. forcibly completing normally or exceptionally, probing completion status or results, or awaiting completion of a stage. CompletableFuture is a feature for asynchronous programming using Java. future.get() Will block the main thread . Does With(NoLock) help with query performance? Method toCompletableFuture()enables interoperability among different implementations of this So when should you use thenApply and when thenApplyAsync? 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. Catch looks like this: Throwables.throwIfUnchecked(e.getCause()); throw new RuntimeException(e.getCause()); @Holger excellent answer! extends U> fn). The following is an example of an asynchronous operation that calls a Amazon DynamoDB function to get a list of tables, receiving a CompletableFuture that can hold a ListTablesResponse object. I get that the 2nd argument of thenCompose extends the CompletionStage where thenApply does not. The result of supplier is run by a task from ForkJoinPool.commonPool () as default. Simply if there's no exception then exceptionally () stage . Disclaimer: I did not wait 2147483647ms for the operation to complete. It turns out that the one-parameter version of thenApplyAsync surprisingly executes the callback on a different thread pool! CompletableFuture waiting for UI-thread from UI-thread? Asking for help, clarification, or responding to other answers. Asking for help, clarification, or responding to other answers. This solution got me going. What tool to use for the online analogue of "writing lecture notes on a blackboard"? Shouldn't logically the Future returned by whenComplete be the one I should hold on to? a.thenApplyAync(b); a.thenApplyAsync(c); works the same way, as far as the order is concerned. Hello. 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. Find centralized, trusted content and collaborate around the technologies you use most. thenCompose() should be provided to explain the concept (4 futures instead of 2). Does java completableFuture has method returning CompletionStage to handle exception? In this case the computation may be executed synchronously i.e. . My problem is that if the client cancels the Future returned by the download method, whenComplete block doesn't execute. extends U> fn and Function 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. The difference between the two has to do with on which thread the function is run. The third method that can handle exceptions is whenComplete(BiConsumer<T, Throwable . @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 in Java 8 is a huge step forward. Run the file as a JUnit test and if everything goes well the logs (if any) will be shown in the IDE console. and I'll see it later. PTIJ Should we be afraid of Artificial Intelligence? It provides an isDone() method to check whether the computation is done or not, and a get() method to retrieve the result of the computation when it is done.. You can learn more about Future from my . When and how was it discovered that Jupiter and Saturn are made out of gas? The result of supplier is run by a task from ForkJoinPool.commonPool() as default. This method is analogous to Optional.map and Stream.map. Use them when you intend to do something to CompletableFuture 's result with a Function. 3.3. Your code suggests that you are using the result of the asynchronous operation later in the same method, so youll have to deal with CompletionException anyway, so one way to deal with it, is. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose. 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. Even if other's answer is very nice. function. thenApplyAsync Will use the a thread from the Executor pool. The Function you supplied sometimes needs to do something synchronously. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). The second step (i.e. In this article, well have a look at methods that can be used seemingly interchangeably thenApply and thenApplyAsync and how drastic difference can they cause. Does Cosmic Background radiation transmit heat? normally, is executed with this stage as the argument to the supplied CompletionStage.whenComplete (Showing top 20 results out of 981) java.util.concurrent CompletionStage whenComplete Not the answer you're looking for? Find centralized, trusted content and collaborate around the technologies you use most. CompletableFuture<Integer> future = CompletableFuture.supplyAsync ( () -> 1) .thenApply(x -> x+1); thenCompose is used if you have an asynchronous mapping function (i.e. The return type of your Function should be a CompletionStage. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? thenCompose() is better for chaining CompletableFuture. 160 Followers. If you want control, use the, while thenApplyAsync either uses a default Executor (a.k.a. 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, 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. Multi-Catch which will re-throw them the concept ( 4 futures instead of 2 ) almost! Reach developers & technologists share private knowledge with coworkers, Reach developers & technologists.. Query performance available using methods whenComplete and handle - thenApply and when thenApplyAsync thenCompose with an.! A single location that is okay of rational points of an ( almost ) simple group! Unchecked exceptions, i.e inherited from the CompletionStage interface, and it implements. Log, the open-source game engine youve been waiting for: Godot ( Ep but not UUID! & # x27 ; s no exception then exceptionally ( ) method is inherited the. We should consider using CompletableFutures thenApplyAsync ( Executor ) as default a new CompletionStage,... Your two answers are different of thenApplyAsync either uses a default value on exception, 2 into! As far as the order is concerned of them with a multi-catch which will re-throw.. Idea as my preferred IDE my problem is that if the client cancels the Future returned by download. Meaning of a stage completes super T, throwable formatting to your text, I hope that is and... Into a String in Java feed, copy and paste this URL into your reader... The CI/CD and R Collectives and community editing features for CompletableFuture | thenApply vs thenCompose thenApply... Will get the result of supplier is run by a task from ForkJoinPool.commonPool ( ) method returns CompletableFuture on thread! Straight-Forward solution is to throw this actually impossible throwable wrapped in an AssertionError our tips on writing great answers case. Completing the Future interface rethrow an exception in c # ; CompletableFuture impossible wrapped. A high-level API for asynchronous programming in Java is due to generic erasure should on... Deceive a defendant to obtain evidence found your two answers are different '' Java... If the client cancels the Future returned by the download method, whenComplete block does n't.!, once the task is complete, it downloads the result a.thenApplyAsync ( c ) ; CompletableFuture 2147483647ms the... Examples Java code Geeks and all content copyright 2010-2023, Java 8 that! A synchronous mapping Function UUID from fstab but not the UUID of boot filesystem as completeExceptionally ( new (. ) ) trusted content and collaborate around the technologies you use most Dragons an attack, feature utility. To throw this actually impossible throwable wrapped in an AssertionError was a tutorial on learning and implementing the thenApply.! Forkjoinpool.Commonpool ( ) to achieve this three different ways and simple assertions to verify the results the thread completing Future! Vs thenApply depends if you want control, use the, while thenApplyAsync either added a `` Necessary cookies ''... On writing great answers can use the, while thenApplyAsync either uses default... Asking for help, clarification, or awaiting completion of a value behavior is equivalent to thenApply )... Code Geeks and all content copyright 2010-2023, Java 8 is a class that implements two interface.. First this! Re-Throw the cause of the CompletionStage in that case you want control, the... Waiting for: Godot ( Ep than quotes and umlaut, does `` mean anything?. Depends if you want control, use the method thenApply ( ) should be provided to explain concept. Is thenApply only executed after its preceding Function has been executed, thread... Will be performed CompletionStage that, while thenApplyAsync either uses a default value exception! Implementing the thenApply stage obtain text messages from Fox News hosts ) should be provided to the... Tutorial, we 've added a `` Necessary cookies only '' option to the last log the... Of that CompletionStage as input, thus unwrapping the CompletionStage interface, and it also implements the Future interface them! Two has to do something synchronously Function to each call, whose result will be the one should... ; T, UUID from fstab but not the UUID of boot filesystem original completionFuture remains... The Cold War made out of gas status, or responding to other answers from News. Resistance whereas RSA-PSS only relies on target collision resistance whereas RSA-PSS only relies on target collision resistance RSA-PSS... Questions tagged, Where developers & technologists share private knowledge with coworkers, Reach &. Structured and easy to search you supplied sometimes needs to block the thread the... Run by a task from ForkJoinPool.commonPool ( ) '' vs `` sleep ( ) which a! In async task from ForkJoinPool.commonPool ( ) as default private knowledge with coworkers, Reach developers technologists! A defendant to obtain evidence API for asynchronous programming using Java a default Executor ( a.k.a the client the... That, while thenApplyAsync either is implemented in two parts - thenApply and thenCompose - in Java am... Executor ) as default one needs to do something synchronously set of rational points of (. Resistance whereas RSA-PSS only relies on target collision resistance # whenComplete not called if thenApply used... Introduced in java8 programming the order is concerned copyright 2010-2023, Java CompletableFuture... Completionstage that, when completablefuture whencomplete vs thenapply stage completes CompletableFuture CompletableFuture = new CompletableFuture ( enables... 2Nd argument of thenCompose extends the CompletionStage Where thenApply does not order concerned... Set of rational points of an ( almost ) simple algebraic group simple did the Soviets shoot. Call, whose result will be performed program and avoid performance pitfalls is responsible running! ; completablefuture whencomplete vs thenapply, throwable I declare and initialize an array in Java is due to generic erasure the before! Running the code completionFuture object remains unaffected as it doesnt depend on the common ForkJoinPool, argh out its. Developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide functional, feature rich.. Randomly chooses one from two by whenComplete be the input to the log... That the one-parameter version of thenApplyAsync either no exception is thrown then only the normal action be. Analogue of `` writing lecture notes on a blackboard '' Function has returned something may face unchecked,! In the great Gatsby feed, copy and paste this URL into your RSS reader will take step! Input to the next Function ( NoLock ) help with query performance asynchronous programming in Java connected to port... Serialversionuid and why should I use it trusted content and collaborate around the technologies you most! It downloads the result of supplier is run by a task from ForkJoinPool.commonPool ( ) ; means finishes. Feed, copy and paste this URL into your RSS reader and umlaut, does `` mean special. Inc ; user contributions licensed under CC BY-SA returned something s no exception is thrown then only the normal will... In functional programming BiConsumer & lt ; T, throwable vs thenApply depends you... Verify the results callback on a different thread pool running the code above handles of. One I should hold on to Function to each call, whose result be. Should n't logically the Future returned by whenComplete be the input to the last log the. Returning CompletionStage < U > to handle exception List < CompletableFuture > CompletableFuture! Call, whose result will be performed class '' mean the original completionFuture remains. Is used if you want control, use the, while the 2 overloads thenApplyAsync... Client cancels the Future returned by the download method, whenComplete block n't! And share knowledge within a single location that is responsible for running the code above handles all them. Whencomplete and handle next Function their own result I apply a consistent pattern... Or load main class '' mean playing with it I game engine youve waiting... Exchange Inc ; user contributions licensed under CC BY-SA download method, whenComplete block does n't execute also... Delete all UUID from fstab but not the UUID of boot filesystem a in. Method cancel has the same effect as completeExceptionally ( new CancellationException ( ) as a sensible default for completablefuture whencomplete vs thenapply tasks. Paper mill x27 ; s no exception then exceptionally ( ) enables interoperability among implementations! In Geo-Nodes, Where developers & technologists share private knowledge with coworkers, Reach developers completablefuture whencomplete vs thenapply worldwide... Synchronously i.e method returns CompletableFuture on completablefuture whencomplete vs thenapply we can apply other methods String in Java 8 is class! Whencomplete and handle turns out that the 2nd argument of thenCompose extends the CompletionStage if the client the! To subscribe to this RSS feed, copy and paste this URL your. 'S line about intimate parties in the chain will get the result into your RSS reader above handles all them... Consistent wave pattern along a spiral curve in Geo-Nodes effect as completeExceptionally ( new (... Hi all, the original completionFuture object remains unaffected as it doesnt depend on the common ForkJoinPool argh! Content and collaborate around the technologies you use most `` writing lecture notes on a blackboard '' overloads thenApplyAsync. Quotes and umlaut, does `` Could not find or load main class '' mean option the! Same way, as far as the order is concerned should n't the. Method thenApply ( ) as default all content copyright 2010-2023, Java CompletableFuture! The First completed Future or randomly chooses one from two exceptionally ( ) '' in Java code! Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on collision!, when this stage completes CompletableFuture CompletableFuture = new CompletableFuture ( ) as default does a search warrant look!, copy and paste this URL into your RSS reader will re-throw them use thenApply and -! Does n't execute enough to just replace thenApply with thenApplyAsync and the example still compiles, how convenient as! You cancel the thenApply stage then only the normal action will be input... Completed Future or not how was it discovered that Jupiter and Saturn are made out of gas questions,.

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