java.util.concurrent.CompletableFuture#applyToEither ( )源码实例Demo

final <V> CompletionStage<V> registerAwaitTarget(CompletionStage<V> originalAwait) {
    blockerVersion.incrementAndGet();
	CompletableFuture<V> terminateMethod = new CompletableFuture<>();
    CompletionStage<V> guardedAwait = terminateMethod.applyToEither(originalAwait, Function.identity());
    // Save references for outer promise cancellation
    this.terminateMethod = terminateMethod;
    this.originalAwait   = originalAwait;
    // Re-check for race with main future cancellation
    cancelAwaitIfNecessary(terminateMethod, originalAwait);
    return guardedAwait;
}
 

/**
 * When an already-contextualized Function is specified as the action/task,
 * the action/task runs with its already-captured context rather than
 * capturing and applying context per the configuration of the managed executor.
 *
 * @throws ExecutionException indicates test failure
 * @throws InterruptedException indicates test failure
 * @throws TimeoutException indicates test failure
 */
@Test
public void contextOfContextualFunctionOverridesContextOfManagedExecutor() throws ExecutionException, InterruptedException, TimeoutException {
    ThreadContext labelContext = ThreadContext.builder()
            .propagated(Label.CONTEXT_NAME)
            .unchanged()
            .cleared(ThreadContext.ALL_REMAINING)
            .build();

    ManagedExecutor executor = ManagedExecutor.builder()
            .propagated(Buffer.CONTEXT_NAME)
            .cleared(ThreadContext.ALL_REMAINING)
            .build();
    try {
        Buffer.set(new StringBuffer("contextualFunctionOverride-buffer-1"));
        Label.set("contextualFunctionOverride-label-1");

        Function<Integer, Integer> precontextualizedFunction1 = labelContext.contextualFunction(i -> {
            Assert.assertEquals(Label.get(), "contextualFunctionOverride-label-1",
                    "Previously captured context type not found on thread.");
            Assert.assertEquals(Buffer.get().toString(), "",
                    "Context type not cleared from thread.");
            return i + 1;
        });

        Buffer.set(new StringBuffer("contextualFunctionOverride-buffer-2"));
        Label.set("contextualFunctionOverride-label-2");

        Function<Integer, Integer> precontextualizedFunction2 = labelContext.contextualFunction(i -> {
            Assert.assertEquals(Label.get(), "contextualFunctionOverride-label-2",
                    "Previously captured context type not found on thread.");
            Assert.assertEquals(Buffer.get().toString(), "",
                    "Context type not cleared from thread.");
            return i + 20;
        });

        Function<Throwable, Integer> precontextualizedErrorHandler = labelContext.contextualFunction(failure -> {
            Assert.assertEquals(Label.get(), "contextualFunctionOverride-label-2",
                    "Previously captured context type not found on thread.");
            Assert.assertEquals(Buffer.get().toString(), "",
                    "Context type not cleared from thread.");
            return -1;
        });

        Buffer.set(new StringBuffer("contextualFunctionOverride-buffer-3"));
        Label.set("contextualFunctionOverride-label-3");

        Function<Integer, Integer> normalFunction = i -> {
            Assert.assertEquals(Buffer.get().toString(), "contextualFunctionOverride-buffer-3",
                    "Previously captured context type not found on thread.");
            Assert.assertEquals(Label.get(), "",
                    "Context type not cleared from thread.");
            return i + 300;
        };

        CompletableFuture<Integer> stage0 = executor.newIncompleteFuture();
        CompletableFuture<Integer> stage1 = stage0.thenApplyAsync(precontextualizedFunction1);

        Buffer.set(new StringBuffer("contextualFunctionOverride-buffer-4"));
        Label.set("contextualFunctionOverride-label-4");

        Function<Integer, CompletableFuture<Integer>> precontextualizedFunction4 = labelContext.contextualFunction(i -> {
            Assert.assertEquals(Label.get(), "contextualFunctionOverride-label-4",
                    "Previously captured context type not found on thread.");
            Assert.assertEquals(Buffer.get().toString(), "",
                    "Context type not cleared from thread.");
            return stage1;
        });

        Buffer.set(new StringBuffer("contextualFunctionOverride-buffer-3"));
        Label.set("contextualFunctionOverride-label-3");

        CompletableFuture<Integer> stage2 = stage0.thenComposeAsync(precontextualizedFunction4);
        CompletableFuture<Integer> stage3 = stage2.applyToEither(stage1, precontextualizedFunction2);
        CompletableFuture<Integer> stage4 = stage3.thenApply(normalFunction);
        CompletableFuture<Integer> stage5 = stage4.thenApply(i -> i / (i - 321)) // intentional ArithmeticException for division by 0
                .exceptionally(precontextualizedErrorHandler);

        stage0.complete(0);

        Assert.assertEquals(stage2.join(), Integer.valueOf(1),
                "Unexpected result for completion stage.");

        Assert.assertEquals(stage5.join(), Integer.valueOf(-1),
                "Unexpected result for completion stage.");
    }
    finally {
        executor.shutdownNow();
        // Restore original values
        Buffer.set(null);
        Label.set(null);
    }
}
 

public <T,U> CompletableFuture<U> applyToEither
    (CompletableFuture<T> f,
     CompletionStage<? extends T> g,
     Function<? super T,U> a) {
    return f.applyToEither(g, a);
}
 

private CompletableFuture<Response> retryOrTimeOut(ClientRequest request) {
    final CompletableFuture<Response> resultFuture = new CompletableFuture<>();
    retryOperation(resultFuture, () -> oneShot(serviceNameResolver.resolveHost(), request), maxRetries);
    CompletableFuture<Response> timeoutAfter = timeoutAfter(readTimeout, TimeUnit.MILLISECONDS);
    return resultFuture.applyToEither(timeoutAfter, Function.identity());
}
 

public <T,U> CompletableFuture<U> applyToEither
    (CompletableFuture<T> f,
     CompletionStage<? extends T> g,
     Function<? super T,U> a) {
    return f.applyToEither(g, a);
}