Hi Brain,
Long time no talk! And thanks for raising the forgotten yet important
issue. :)
On 10/25/07, Brian McCallister <[EMAIL PROTECTED]> wrote:
> For the Java 5 dependent branches, it would be awfully nice if we were
> to make IoHandler and IoFilter type safe with regard to received
> messages.
>
> This can be done two ways -- the first is mere decoration -- you add a
> type parameter for the message argument:
>
> interface IoHandler<In> {
> messageReceived(IoSession session, In msg);
> ...
> }
>
> interface IoFilter<In, Out> {
> messageReceived(NextFilter<Out>, IoSession session, In msg);
> }
Do we need Out parameter for IoFilter and NextFilter? I thought we
don't. Please let me know if I am missing something.
> In the "Decoration" approach the type is ignored at runtime and just
> becomes an implicit cast. This lets you type what comes in as
> documentation, at least.
>
> A stronger approach would be to explicitly check the generic type via
> reflection and raise an exception at bind() or connect() time. In this
> case the In and Out types for the filter chain would be compared for
> compatibility, and the final out on the filter chain compared to the
> In on the handler. This would allow for raising an illegal state
> exception describing the message type problem as early as possible.
> Once running implicit casts are used for actual dispatch so as not to
> impact performance.
Because a filter chain can be modified at any time, such kind of
sanity check must be done whenever filter chain is modified (i.e. when
a filter is added or removed.)
Moreover, if the Out parameter of IoFilter is just for checking type
safety, it should be removed IMHO because we can still rely on JVM for
type safety, which will be found very easily in integration test time.
Also, there was a similar discussion:
https://issues.apache.org/jira/browse/DIRMINA-372
No conclusion yet. However, people seem to prefer to retain the
current IoHandler and IoFilter interface. Instead, Niklas's idea is
gaining attraction. WDYT?
Cheers,
Trustin
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