How to translate an exception thrown from Stream.onClose handler?

[Timo Kinnunen]

Consider a case where a stream is processed in steps from one form into another, possible many times in succession. The pseudo-code view of it might look like this: 


Stream<String> readIncomingDataToLines();

Stream<Document> fromLinesToDocuments(Stream<String> lines);

Stream<Path> fromDocumentsToFiles(Stream<String> documents);

Stream<?> fromFilesToDotDotDot(Stream<Path> files);


Suppose one upstream step needs to add an onClose handler to the Stream and that handler throws an unchecked RuntimeException as normal

.

The consumers downstream don’t know about an arbitrary low-level exception and don’t care that much either. At the same time, the low-level translator step doesn’t know about higher-level processing steps and shouldn’t have to care in the first place.


So how and where should that RuntimeException be translated into something else?








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