[英]Catch RuntimeException thrown in a lambda and rethrow it as checked
我試圖找出為什么我的代碼拋出IllegalStateException
,而不是我的自定義,我希望它拋出。
public final class CollectorUtils {
private CollectorUtils() {
throw new UnsupportedOperationException();
}
public static <E, R, X extends Throwable> Collector<E, ?, R> listAndThenCollector(final Predicate<List<E>> listPredicate, final Function<List<E>, R> listFunction, final Function<Throwable, X> exceptionWrapper) throws X {
Objects.requireNonNull(listPredicate);
Objects.requireNonNull(listFunction);
Objects.requireNonNull(exceptionWrapper);
try {
return Collectors.collectingAndThen(Collectors.toList(), list -> {
if (!listPredicate.test(list)) {
throw new IllegalStateException(); //Line that throws the exception
}
return listFunction.apply(list);
});
} catch (IllegalStateException ex) {
throw exceptionWrapper.apply(ex);
}
}
public static <E> Collector<E, ?, E> singleElementCollector() throws NotASingleElementException {
return listAndThenCollector(list -> list.size() == 1, list -> list.get(0), NotASingleElementException::new);
}
}
IllegalStateException
被拋出:line throw new IllegalStateException()
。
用法示例:
public static void test() {
try {
Integer result = IntStream.range(0, 2)
.boxed()
.collect(CollectorUtils.singleElementCollector());
} catch (NotASingleElementException ex) {
Logger.getLogger(CollectorUtils.class.getName()).log(Level.SEVERE, null, ex);
}
}
這段代碼應拋出NotASingleElementException
,而不是拋出IllegalStateException
,我怎么能讓它工作?
做一個實際的工作時錯誤的行為:
Exception in thread "pool-3-thread-1" java.lang.IllegalStateException
at dpc2.base.utils.CollectorUtils.lambda$listAndThenCollector$0(CollectorUtils.java:28)
at dpc2.base.utils.CollectorUtils$$Lambda$21/2071035411.apply(Unknown Source)
at java.util.function.Function.lambda$andThen$6(Function.java:88)
at java.util.function.Function$$Lambda$22/63121782.apply(Unknown Source)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:503)
at dpc2.base.utils.ImageMagickUtils.convertPDFToTIFF(ImageMagickUtils.java:30)
at dpc2.server.convert.ConvertConsumer.accept(ConvertConsumer.java:20)
at dpc2.server.convert.ConvertConsumer.accept(ConvertConsumer.java:14)
at dpc2.base.checker.BaseChecker.lambda$null$0(BaseChecker.java:116)
at dpc2.base.checker.BaseChecker$$Lambda$15/2121862243.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:744)
您的收集器已返回但未在listAndThenCollector
方法中收集。 實際的收集發生在:
.collect(CollectorUtils.singleElementCollector());
這是你的測試方法。 那是拋出異常的時候。
我會說這是因為當你調用Collectors.collectingAndThen
你傳遞一個當時沒有執行的lambda。 當它最終執行時,你的捕獲不再是捕獲它。
你不能用:
//throw new IllegalStateException();
throw exceptionWrapper.apply(new IllegalStateException());
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