请求将基于CompletableFuture的方法转换为Reactor或Akka实现

Got it, let's walk through converting your CompletableFuture parallel execution code to both Reactor (Project Reactor, commonly used in Spring WebFlux) and Akka implementations. First, let's finish out your original code to make the comparison clear—since it cut off mid-way, I'm assuming it waits for all futures to complete and assembles the results into an AClass instance.

Original CompletableFuture Code (Completed) #

public AClass aMethod() {
    CompletableFuture<SomeClassA> someClassAFuture = CompletableFuture.supplyAsync(() -> someMethodThatReturnsA());
    CompletableFuture<SomeClassB> someClassBFuture = CompletableFuture.supplyAsync(() -> someMethodThatReturnsB());
    CompletableFuture<SomeClassC> someClassCFuture = CompletableFuture.supplyAsync(() -> someMethodThatReturnsC());
    
    try {
        // Wait for all tasks to finish
        CompletableFuture.allOf(someClassAFuture, someClassBFuture, someClassCFuture).get();
        
        // Assemble results into AClass
        return new AClass(
            someClassAFuture.get(),
            someClassBFuture.get(),
            someClassCFuture.get()
        );
    } catch (InterruptedException | ExecutionException e) {
        throw new RuntimeException("Failed to fetch all results", e);
    }
}

Reactor is built around non-blocking, reactive streams. We'll cover both the recommended non-blocking approach and a blocking fallback if you need a synchronous return.

Non-Blocking (Recommended) #

This returns a Mono<AClass> (Reactor's async type) to keep things non-blocking, which aligns with reactive best practices:

import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;

public Mono<AClass> aMethodReactor() {
    // Wrap blocking methods in Mono and offload to a dedicated scheduler for blocking work
    Mono<SomeClassA> aMono = Mono.fromCallable(this::someMethodThatReturnsA)
        .subscribeOn(Schedulers.boundedElastic());
    
    Mono<SomeClassB> bMono = Mono.fromCallable(this::someMethodThatReturnsB)
        .subscribeOn(Schedulers.boundedElastic());
    
    Mono<SomeClassC> cMono = Mono.fromCallable(this::someMethodThatReturnsC)
        .subscribeOn(Schedulers.boundedElastic());
    
    // Combine all three results when they complete, then map to AClass
    return Mono.zip(aMono, bMono, cMono)
        .map(tuple -> new AClass(tuple.getT1(), tuple.getT2(), tuple.getT3()))
        .onErrorMap(e -> new RuntimeException("Failed to fetch all results", e));
}

Key Notes: #

• Mono.fromCallable wraps blocking operations (use Mono.fromSupplier if your methods are non-blocking).
• subscribeOn(Schedulers.boundedElastic()) ensures blocking work doesn't clog the main event loop—critical for reactive applications.
• Mono.zip waits for all three tasks to finish before combining their results into a tuple.

Blocking (If You Need a Synchronous Return) #

If you must return a concrete AClass instead of a reactive type, use block() (not ideal for non-blocking apps, but matches your original code's behavior):

public AClass aMethodReactorBlocking() {
    Mono<SomeClassA> aMono = Mono.fromCallable(this::someMethodThatReturnsA)
        .subscribeOn(Schedulers.boundedElastic());
    
    Mono<SomeClassB> bMono = Mono.fromCallable(this::someMethodThatReturnsB)
        .subscribeOn(Schedulers.boundedElastic());
    
    Mono<SomeClassC> cMono = Mono.fromCallable(this::someMethodThatReturnsC)
        .subscribeOn(Schedulers.boundedElastic());
    
    try {
        return Mono.zip(aMono, bMono, cMono)
            .map(tuple -> new AClass(tuple.getT1(), tuple.getT2(), tuple.getT3()))
            .block(); // Block to get the synchronous result
    } catch (RuntimeException e) {
        throw new RuntimeException("Failed to fetch all results", e);
    }
}

Akka uses CompletionStage (compatible with Java's CompletableFuture) for async operations. We'll cover both non-blocking and blocking variants.

Non-Blocking (Akka's Async Style) #

Returns a CompletionStage<AClass> to maintain async behavior:

import akka.actor.ActorSystem;
import java.util.concurrent.CompletionStage;

public class AkkaAsyncExample {
    private final ActorSystem system;

    public AkkaAsyncExample(ActorSystem system) {
        this.system = system;
    }

    public CompletionStage<AClass> aMethodAkka() {
        // Execute each task on Akka's dispatcher (use a custom dispatcher for blocking work if needed)
        CompletionStage<SomeClassA> aFuture = system.dispatcher().execute(() -> someMethodThatReturnsA());
        CompletionStage<SomeClassB> bFuture = system.dispatcher().execute(() -> someMethodThatReturnsB());
        CompletionStage<SomeClassC> cFuture = system.dispatcher().execute(() -> someMethodThatReturnsC());
        
        // Combine results step-by-step
        return aFuture.thenCombine(bFuture, AAndB::new)
            .thenCombine(cFuture, (ab, c) -> new AClass(ab.a, ab.b, c))
            .exceptionally(e -> {
                throw new RuntimeException("Failed to fetch all results", e);
            });
    }

    // Helper class to hold intermediate results
    private static class AAndB {
        public final SomeClassA a;
        public final SomeClassB b;
        public AAndB(SomeClassA a, SomeClassB b) {
            this.a = a;
            this.b = b;
        }
    }
}

Blocking (Synchronous Return) #

If you need a concrete AClass, convert the CompletionStage to a CompletableFuture and block:

public AClass aMethodAkkaBlocking() {
    try {
        return aMethodAkka().toCompletableFuture().get();
    } catch (InterruptedException | ExecutionException e) {
        throw new RuntimeException("Failed to fetch all results", e);
    }
}

Key Notes: #

• Akka's dispatcher() handles async task execution—configure a dedicated blocking dispatcher if your someMethodThatReturnsX calls are long-running I/O operations.
• thenCombine chains async results to assemble the final AClass without blocking.

内容的提问来源于stack exchange，提问作者italktothewind