[jira] [Created] (IGNITE-18049) Cursor#close() should not declare any exceptions in throws clause

["Roman Puchkovskiy (Jira)" <ji...@apache.org>]

Roman Puchkovskiy created IGNITE-18049:
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             Summary: Cursor#close() should not declare any exceptions in throws clause
                 Key: IGNITE-18049
                 URL: https://issues.apache.org/jira/browse/IGNITE-18049
             Project: Ignite
          Issue Type: Improvement
            Reporter: Roman Puchkovskiy
            Assignee: Roman Puchkovskiy
             Fix For: 3.0.0-beta2


When an {{AutoCloseable}} subinterface/implementation declares {{throws Exception}} in its {{close()}} method, it makes it very inconvenient to work with such a type using try-with-resources because the using code must use something like {{catch (Exception e)}} which makes it difficult to process exceptions that might arise in the {{try}} block.

The suggestion is to make {{Cursor#close()}} not declare any checked exceptions. Most of the current implementations of {{Cursor}} already obey to this restriction, and a few that don't can be easily reworked to obey.

The only problem is adapters (when we adapt an {{Iterator}} producing a {{{}Cursor{}}}). Here, we must be prepared to get an {{Iterator}} that is a resource itself (is an {{{}AutoCloseable{}}}) and hence needs to be closed when the cursor is closed. But {{AutoCloseable#close()}} might throw a checked exception. It is unacceptable to swallow it, and it is not too good to just automatically wrap it in an unchecked exception.
 # The best thing is that developers (who know their resources) write their own custom {{Cursor}} implementations handling the closure.
 # We also need a way to adapt 'safe close' iterators (obtained from in-memory collections, for example). We should add a method like {{Cursor#fromPurIterator(Iterator)}} that will check (at the moment of invocation that the provided iterator is NOT an AutoCloseable and will throw if it is)
 # We can also provide a generic way to adapt a closeable iterator with a method like {{<IT extends Iterator<T> & AutoCloseable> Cursor#fromCloseableIterator(IT iterator)}} adding a Javadoc urging the user to use this method only when absolutely necessary
 # We probably should not add an omnivorous method that could adapt both pure and closeable iterators for now to prevent abuses.



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