Async java8
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This document discusses asynchronous programming in Java 8 using CompletableFuture. It introduces key concepts like asynchronous vs synchronous execution, and asynchronous patterns like callbacks. It then covers the main CompletableFuture methods for creating asynchronous tasks, chaining and combining tasks, and handling exceptions. The main points are that CompletableFuture provides tools to chain, combine and handle asynchronous tasks in a way that is easier to read and maintain compared to callbacks.
Async java8
- 1. Think Async in Java 8
- 2. 2 Asynchronous Asynchronous Multi threading Way to Think in Async
- 9. Asynchronous ✗ It can be really faster ✗ Its non-blocking ✗ No gap between tasks 9
- 10. Asynchronous vs Multi-thread ✗ Synchronous Single Threaded ✗ Synchronous Multi-Threaded ✗ Asynchronous Single Threaded ✗ Asynchronous Multi-Threaded 10
- 11. 11 Asynchronous in Java Runnable Java 1 Do not have the option to notify in case of any error
- 12. 12 Asynchronous in Java Runnable Callable Java 1 Java 5 Have option to notify in case of any error
- 13. 13 Asynchronous in Java Runnable Callable Executer Service Java 1 Java 5 Java 5 Future Java 5
- 14. Asynchronous use case 14 Callable<String> task = () --‐> "select user from User" executorService.submit (task) Future<String>
- 16. Future 16 main Thread 1 Submit() get() Result ready Blockingthemain thread
- 17. 17 Future main Thread 1 Submit() get() Result ready Don’t have the ability to attach a callback function
- 18. 18 Asynchronous use case main Thread 1 Thread 2 Thread 3 task1 task2 task3 task4
- 19. 19 Asynchronous use case main Thread 1 Thread 2 Thread 3 task1 task2 task3 task4 Multiple Futures cannot be chained together
- 20. 20 Asynchronous use case Can not combine multiple Futures together
- 21. “We have to make callback” 21
- 22. 22 Callbacks Main Thread Thread pool Event Timer File I/O User code Async API Calls Callback method
- 23. 23 Callbacks public void processAsync( ExecutorService executor, Supplier supplier, Consumer onSuccess ) { executor.submit(() -> { List lines = supplier.get(); onSuccess.accept(lines); }); } Consumer onSuccess onSuccess.accept(lines);
- 24. 24 Callbacks public void processAsync( ExecutorService executor, Supplier supplier, Consumer onSuccess , Consumer onFail ) { executor.submit(() -> { try { List lines = supplier.get(); onSuccess.accept(lines); catch(Exception e) { onFail.accept(e); } }); } Consumer onSuccess Consumer onFail onSuccess.accept(lines); onFail.accept(e);
- 25. Drawbacks of Callbacks ✗ Do not scale well for even moderately complex asynchronous code ✗ Multiple callback function hard to read, easy to break, and hard to debug 25
- 26. “How to achieve asynchronicity in java” 26
- 27. We have new tools in Java 8 to handle this precise case It brings new solutions to chain tasks 27 Asynchronous in Java 8
- 28. Handle both asynchronous and multithreaded programming 28 Asynchronous in Java 8
- 30. 30 CompletableFuture Intro Future<T> Completion Stage<T> Completable Future<?> ✗ task may be running ✗ task may have Complete normally ✗ task may have complete exceptionally It has a state:
- 32. 32 Creating Method ✗ new ✗ supplyAsync() ✗ runAsync()
- 33. 33 Creating a CompletableFuture CompletableFuture<String> cf = new CompletableFuture<>(); String result = cf.get(); String result = cf. complete(“ Killed !! ”); ` CompletableFuture With no-arg constructor Blocks until the Future is complete Complete a Future manually
- 34. 34 Running asynchronous ExecutorService es = Executors.newCachedThreadPool(); es.execute (new Runnable() { public void run() { System.out.print("Hello Java“); } }); CompletableFuture<Void> cf = CompletableFuture.runAsync ( () -> { System.out.print("Hello Java“); }); Java 7 Java 8 es.execute CompletableFuture.runAsync
- 35. 35 Running asynchronous ExecutorService es = Executors.newCachedThreadPool(); Future<String> future = es.submit(new Callable<String>() { public String call() throws Exception { return "Hello Java"; } }); CompletableFuture<String> cf = CompletableFuture.supplyAsync(() -> { return "Hello Java"; }); Java 7 Java 8 es.submit CompletableFuture.supplyAsync
- 36. 36 Create Method ✗ CompletableFuture() cf = new CompletableFuture(); ✗ CompletableFuture<U> :: supplyAsync( Supplier<U>supplier ) ✗ CompletableFuture<U> :: runAsync ( Runnable runnable ) Supplier<U>supplier Runnable runnable
- 37. 37 Create Method ✗ CompletableFuture<U> :: supplyAsync (Supplier<U>supplier) ✗ CompletableFuture<U> :: runAsync (Runnable runnable) supplyAsync runAsync ForkJoinPool :: commonPool()
- 38. 38 Create Method ✗ CompletableFuture<U> :: supplyAsync ( Supplier<U>supplier , Executor executor ) ✗ CompletableFuture<U> :: runAsync(Runnable runnable , ,Executor executor ) Executor executor Executor executor
- 39. 39 Attach Callback Method ✗ thenApply() ✗ thenAccept() ✗ thenRun()
- 40. 40 thenApply CompletableFuture<String> cf = CompletableFuture.supplyAsync(() -> { return "Hello "; }).thenApply ( s -> { return s + "World "; }).thenApply (s -> { return "First " + s + " Programe!!"; }); thenApply thenApply cf.get() “First Hello World Programe”
- 41. 41 thenAccept CompletableFuture.supplyAsync(() -> { return "Hello "; }).thenApply ( s -> { return s + "World "; }).thenApply (s -> { return "First " + s + " Programe!!"; }).thenAccept (result -> { System.out.print(result); }); thenAccept cf.get() “First Hello World Programe”
- 42. 42 thenRun CompletableFuture.supplyAsync(() -> { return "Hello "; }).thenApply ( s -> { return s + "World "; }).thenRun (() -> { //TODO: some other work }); thenRun
- 43. 43 Async Callback CompletableFuture.supplyAsync(() -> { return "Hello "; }).thenApply ( s -> { return s + "World "; }); CompletableFuture.supplyAsync(() -> { return "Hello "; }).thenApplyAsync ( s -> { return s + "World "; }); thenApply Executed in the same thread where the supplyAsync() task is executed thenApplyAsync Executed in a different thread from ForkJoinPool.commonPool()
- 44. 44 Combining together ✗ thenCompose() ✗ thenCombine() ✗ allOf() ✗ anyOf()
- 45. 45 thenCompose CompletableFuture<User> cf = CompletableFuture.supplyAsync((Long id) -> { return getUserInfo(id); }); CompletableFuture<User> I wanted to call the method inside the user object and also need to chain..?
- 46. 46 thenCompose CompletableFuture<String> cf = CompletableFuture.supplyAsync((Long id) -> { return getUserInfo(id); }). thenCompose (user -> { return user.getName(); }); thenCompose Monads thenApply thenCompose
- 47. 47 thenCombine CompletableFuture<String> cf1 = CompletableFuture.supplyAsync(() -> "Hello“ CompletableFuture<String> cf2 = CompletableFuture.supplyAsync(() -> “World“ CompletableFuture<String> result = cf1.thenCombine (cf2, (s1, s2) -> { s1 + s2 } );thenCombine ( s1, s2 ) -> { s1 + s2 } Callback method is invoked both task is completed
- 48. 48 allOf and anyOf ✗ CompletableFuture <Void> :: allOf ( CompletableFuture<?>... Cfs ) ✗ CompletableFuture <Object> :: anyOf ( CompletableFuture<?>... cfs ) CompletableFuture<?>... cfs CompletableFuture<?>... cfs <Void> <Object>
- 49. 49 Exception Handling ✗ exceptionally() ✗ handle()
- 50. 50 exceptionally CompletableFuture.supplyAsync(() -> { //TODO: some work here }). exceptionally ( ex -> { System.out.print(“exception occurred in future:” + ex); //TODO: some other work }); exceptionally ex
- 51. 51 handle CompletableFuture.supplyAsync(() -> { //TODO: some work here }). handle (( res, ex ) -> { //TODO: some other work }); handle res, ex It is called whether or not an exception occurs
- 52. 52 CompletableFuture for Async When we program asynchronously we usually think in terms of workflows, events and tasks ✗ Do this then that ✗ Do this and/or that ✗ Do this on failure Chaining Joining Recovering
Editor's Notes
- #19: The Future interface was added in Java 5 to serve as a result of an asynchronous computation, but it did not have any methods to combine these computations or handle possible errors.
- #20: The Future interface was added in Java 5 to serve as a result of an asynchronous computation, but it did not have any methods to combine these computations or handle possible errors.