[configuration] CombinedConfiguration.getSource()

["ralph.goers @dslextreme.com" <rg...@apache.org>]

I don't understand why getSource throws an Exception when a property can be
found in multiple configurations. If the property is not a list or if
escaping is disabled then the value from the first Configuration the key is
found in will be used. Shouldn't an Exception only be thrown when the value
is constructed by merging values from two Configurations? (This only seems
to happen if a String with the escape character is present). I'm writing a
class that extends CombinedConfiguration and I wanted to changed this
behavior so that it works that way but unfortunately findSourceConfiguration
is private instead of protected so I can't reimplement getSource without
also reimplementing findSourceConfiguration.

Re: [configuration] CombinedConfiguration.getSource()

[Ralph Goers <ra...@dslextreme.com>]

Oliver Heger wrote:
>
>
> The getSource() method was added on behalf of CONFIGURATION-215 [1]. 
> The original request was a bit adapted to come to a more generic 
> solution. IIRC the usage scenario was that you have multiple child 
> configurations with different name spaces and want to uniquely 
> identify the child configuration that added a specific key. If 
> multiple child configurations define the key in question, no unique 
> source can be identified; hence the exception.
>
> Do you propose making findSourceConfiguration() protected? I did not 
> do this in the past because I was not sure whether there would be 
> another use case for this method and I wanted to keep the API lean. 
> But if you need it, I am not against this change.
>
>
No, I wouldn't necessarily make it protected. It would be a bad idea to 
have some classes have the method behave in one manner while in another 
it behaves differently. 

I ran into this problem because my use cases involve a combined 
configuration where all the defaults are in the base configuration and 
the first configuration contains values that override the defaults. I 
was simply trying to write a unit test that listed the source for each 
key to verify my new class was working properly.

I don't want to distract things by going into the details of this (I'll 
do that when I submit the code), but in this case getSource seems to be 
completely useless as it throws an exception for every key that is 
defined in the override file.  For the purposes you are suggesting a 
better method name would have been getUniqueSource().  For my purposes 
adding a getFirstSource() method would make sense. This would never 
throw an exception but would either return the first configuration 
containing the key or would return null. The only question would be what 
to do about Lists. In all my use cases I will be disabling this behavior 
as I never want to combine the data from multiple configurations.

Ralph

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
For additional commands, e-mail: dev-help@commons.apache.org

Re: [configuration] CombinedConfiguration.getSource()

[Oliver Heger <ol...@oliver-heger.de>]

ralph.goers @dslextreme.com schrieb:
> I don't understand why getSource throws an Exception when a property can be
> found in multiple configurations. If the property is not a list or if
> escaping is disabled then the value from the first Configuration the key is
> found in will be used. Shouldn't an Exception only be thrown when the value
> is constructed by merging values from two Configurations? (This only seems
> to happen if a String with the escape character is present). I'm writing a
> class that extends CombinedConfiguration and I wanted to changed this
> behavior so that it works that way but unfortunately findSourceConfiguration
> is private instead of protected so I can't reimplement getSource without
> also reimplementing findSourceConfiguration.
> 

The getSource() method was added on behalf of CONFIGURATION-215 [1]. The 
original request was a bit adapted to come to a more generic solution. 
IIRC the usage scenario was that you have multiple child configurations 
with different name spaces and want to uniquely identify the child 
configuration that added a specific key. If multiple child 
configurations define the key in question, no unique source can be 
identified; hence the exception.

Do you propose making findSourceConfiguration() protected? I did not do 
this in the past because I was not sure whether there would be another 
use case for this method and I wanted to keep the API lean. But if you 
need it, I am not against this change.

Oliver

[1] https://issues.apache.org/jira/browse/CONFIGURATION-215

---------------------------------------------------------------------
To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
For additional commands, e-mail: dev-help@commons.apache.org