Exception handling with SimpleApplicationEventMulticaster [SPR-11551]

[spring-projects-issues]

cemo koc opened SPR-11551 and commented

org.springframework.context.event.SimpleApplicationEventMulticaster is responsible to multicast event to appropriate listeners.

An exception which is not handled by user is causing to stop other listeners. This behaviour can be annoying if you have 3rd party event listeners which are not handling exceptions. I think that an event listener should not prevent other listeners in case an error. For example, after a login event we are doing some sort of things one by one. Updating some tables, some numbers, calling a restful web service etc... An exception which is not caught is causing to stop other listeners.

I am considering two alternative approach:

Try-Catch and Log Only

In this approach all exceptions must be caught and logged.

Try-Catch and Throw Again at the end

The second approach I am considering is that an exception must be caught and after all can be thrown again.

What do you think?

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Affects: 3.2.8

Referenced from: commits 49916bb

[spring-projects-issues]

Juergen Hoeller commented

Agreed that "try-catch and log only" is a worthwhile option here; throwing at the end would be a bit odd in case of multiple listeners throwing exceptions. In custom scenarios, I'd rather imagine specific listener exceptions to be significant while others can safely get suppressed.

In any case, rather than baking in hard-coded strategies, SimpleApplicationEventMulticaster supports a configurable ErrorHandler strategy, along the lines of our scheduling support. The default is straight propagation; a custom ErrorHandler (or the ones from Spring's existing TaskUtils helper) can generally or selectively catch and log exceptions. For policies that require the listener and the event object as decision-making context, SimpleApplicationEventMulticaster also provides an overridable "invokeListener" template method now.

Juergen

[spring-projects-issues]

cemo koc commented

ErrorHandler seems perfect solution. Thank you.