[jboss-dev] throws Throwable

[Brian Stansberry]

Carlo de Wolf wrote:
> Jason T. Greene wrote:
>> Carlo de Wolf wrote:
>>> Andrew Lee Rubinger wrote:
>>>> Jason T. Greene wrote:
>>>>> Max Rydahl Andersen wrote:
>>>>>>
>>>>>>
>>>>>> Tim Fox wrote:
>>>>>>> David M. Lloyd wrote:
>>>>>>>> On 05/05/2009 03:02 AM, Carlo de Wolf wrote:
>>>>>>>>> What's the use case for having a public method: 
>>>>>>>>> doSomething(Object someArgs...) throws Throwable ? 
>>>>>>>>
>>>>>>>> No valid use cases exist afaik.  Any method that throws 
>>>>>>>> Throwable should die, if it's within our power to kill it. 
>>>>>>> Declaring a method as "throws Throwable" forces the caller to 
>>>>>>> handle the exception even if the exception/error thrown is 
>>>>>>> unchecked.
>>>>>> Then do throws RuntimeException
>>>>>>
>>>>>> Error's are *nonrecoverable* since they are OutOfMemory or hard VM 
>>>>>> errors.No client can ever recover sanely.
>>>>>
>>>>> One valid case for throwing Throwable is a generic invocation 
>>>>> mechanism
>>>>> (interceptors, proxies, etc).
>>>>
>>>> Just because it's generic doesn't mean the caller can do anything 
>>>> about it.  In that case why not just "throws Exception"?
>>> As per javax.interceptor.InvocationContext.proceed().
>>> But InvocationHandler.invoke throws a Throwable, which I think is wrong.
>>
>> IMO this is correct because the Java language allows user code to 
>> throw errors, and an interceptor should be able to throw any exception 
>> declared by the method it is emulating. The only alternative is to 
>> wrap it with a special exception that gets unwrapped, but this is just 
>> pointless copying.
>>
> I disagree: it should be: invoke(..) throws Exception.
> Both the user code and the invoke can throw unchecked exceptions 
> nonetheless. It's the handling of a checked exception that doesn't fit 
> the given method signature that gets special treatment.
> Ergo throws Throwable in this case is still wrong.
> 

The user code can also throw new Throwable(...). Not an Error, not an 
Exception, just a Throwable. Any code that did that should be taken out 
and shot, but it is allowed. And per section 11.2 of the JLS, that's a 
checked exception:

"The unchecked exceptions classes are the class RuntimeException and its 
subclasses, and the class Error and its subclasses. All other exception 
classes are checked exception classes. "

> Carlo
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-- 
Brian Stansberry
Lead, AS Clustering
JBoss, a division of Red Hat
brian.stansberry at redhat.com