👀 Views: 48 💬 Answers: 1 📅 Created: 2025-06-02

spring completablefuture async java-20 Java

I've been banging my head against this for hours. I'm a bit lost with I've been banging my head against this for hours..... I'm working on a personal project and I'm encountering an issue with Java 20 when using `CompletableFuture` in conjunction with Spring's `@Async` annotation. I have a service method annotated with `@Async`, which is supposed to execute asynchronously. However, I notice that the `CompletableFuture` occasionally returns `null` despite the fact that the method is supposed to return a non-null value. For example, I have the following method in my service class: ```java @Service public class MyService { @Async public CompletableFuture<String> asyncMethod() throws InterruptedException { Thread.sleep(1000); return CompletableFuture.completedFuture("Result"); } } ``` In my controller, I call this method like this: ```java @RestController public class MyController { private final MyService myService; public MyController(MyService myService) { this.myService = myService; } @GetMapping("/test") public ResponseEntity<String> testAsync() throws ExecutionException, InterruptedException { CompletableFuture<String> future = myService.asyncMethod(); return ResponseEntity.ok(future.get()); } } ``` In some cases, when I make the GET request to `/test`, I get a response with the expected result, but other times, I receive a null value. I have verified that there are no exceptions being thrown and that the method executes successfully, which leads me to believe the issue might be related to the way Spring handles the asynchronous execution. I've also ensured that the `@EnableAsync` annotation is present in my main application class. Here are the dependencies in my `pom.xml`: ```xml <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-aop</artifactId> </dependency> ``` I've tried wrapping the `CompletableFuture` calls in a `try-catch` block to capture any exceptions, but none are thrown. I suspect it might have something to do with thread management or how the Spring context is configured. Any insights or suggestions on how to debug this issue would be greatly appreciated! Am I missing something obvious? Is this even possible? I'm developing on Linux with Java. I'd really appreciate any guidance on this. I'm using Java 3.9 in this project. I'm open to any suggestions.