如何在可完成的未来识别空指针异常？

Question

我有一个可抛出 NPE 的可完成的未来代码。我无法在本地重现异常。

我已尝试对代码进行验收测试和单元测试，但没有给出准确的错误响应。

    final List<CompletableFuture<Map<K, V>>> completableFutures = 
    copy.stream()                                                                         
    .map(copy -> getRespForId(requestContext, copy))                                                                          
    .collect(Collectors.toList());

    return CompletableFuture.allOf(completableFutures.toArray(new CompletableFuture<?>[0]))
               .thenApply(future -> completableFutures.stream()
                                        .map(CompletableFuture::join)
                                        .flatMap(longMap -> longMap.entrySet().stream())
                                        .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue)));

预计是

Caused by: java.util.concurrent.CompletionException: java.lang.NullPointerException
    at java.base/java.util.concurrent.CompletableFuture.encodeThrowable(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture.completeThrowable(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture.postComplete(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture.postFire(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture$UniApply.tryFire(Unknown Source)
    at java.base/java.util.concurrent.CompletableFuture$Completion.exec(Unknown Source)
    at java.base/java.util.concurrent.ForkJoinTask.doExec(Unknown Source)
    at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(Unknown Source)
    at java.base/java.util.concurrent.ForkJoinPool.scan(Unknown Source)
    at java.base/java.util.concurrent.ForkJoinPool.runWorker(Unknown Source)
    at java.base/java.util.concurrent.ForkJoinWorkerThread.run(Unknown Source)
Caused by: java.lang.NullPointerException: null
    at java.base/java.util.Objects.requireNonNull(Unknown Source)
    at java.base/java.util.stream.Collectors.lambda$uniqKeysMapAccumulator(Unknown Source)

Answer 1

这里的问题不是键而是值。你得到这个异常是因为一个值是空的。看起来 java.util.stream.Collectors#uniqKeysMapAccumulator 检查 Objects.requireNonNull 值。参见 NullPointerException in Collectors.toMap with null entry values

如何在可完成的未来识别空指针异常？

How do I identify the null pointer exception in completable future?

rest

asynchronous

spring-boot

completable-future

java-11