Add support for the handling of ExecutionExceptions
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Key: LANG-499
URL: https://issues.apache.org/jira/browse/LANG-499
Project: Commons Lang
Issue Type: New Feature
Affects Versions: 2.4
Reporter: Oliver Heger
Priority: Minor
Exceptions of the checked type {{ExecutionException}} are thrown by the Java
1.5 task execution framework if the execution of a task fails. Dealing with
these exceptions is somewhat cumbersome as they wrap all kinds of possible
error conditions: checked exceptions, runtime exceptions, and errors as well.
Therefore in _Java Concurrency in Practice_ (JCIP) the following approach is
suggested:
* First inspect the root cause of the exception and check whether it is one of
the possible checked exceptions. If this is the case, re-throw the checked
exception (after a type cast).
* After that call the utility method {{launderThrowable()}}.
{{launderThrowable()}} deals with errors and runtime exceptions and throws them
accordingly.
This approach ensures that all possible exception types are correctly extracted
from an {{ExecutionException}} and passed to the caller.
This ticket is about adding support for this exception extraction process to
_Commons Lang_.
With regards to checked exceptions, there is probably nothing we can do to
simplify exception handling as Java does not allow throwing arbitrary checked
exceptions from a method. However, we could at least add a method like
{{launderThrowable()}} to an utility class (e.g. {{ConcurrentUtils}}, which
could provide other functionality related to the _concurrent_ package as well).
We could also go a step further and define a custom Exception class, say
{{ConcurrentException}}, which plays a similar role as {{ExecutionException}},
but is guaranteed to wrap only a checked exception. An utility method
converting {{ExecutionException}} to {{ConcurrentException}} would - like
{{launderThrowable()}} - check for runtime exceptions and errors and handle
them directly. All other exceptions are wrapped in a {{ConcurrentException}}.
In cases where no checked exceptions are needed or desired, also a runtime
version ({{ConcurrentRuntimeException}}) could be provided.
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