commons-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Greg Torrance <greg.torra...@pobox.com>
Subject Re: [configuration] Combined Configuration examples
Date Sun, 13 Nov 2016 20:54:54 GMT
Thanks Oliver.

I think I understand what you're saying about why Channel 4 would not be 
included with the OverrideCombiner (if it doesn't exist in 
testfile1.xml). I am sorry to hear, though, that attributes are not used 
at all for matching with OverrideCombiner. If I'm understanding it 
correctly, that means it can't really be used for overriding just 
specific list items, as the entire list would have to be represented, in 
the same order, in both primary and overriding files, or the wrong list 
item might be overridden. (For example, if the primary list had Channels 
1, 2, and 3, and the override list had only Channel 2, then it would 
attempt to override Channel 1 with the info from Channel 2.) Is my 
understanding correct?

Anyway, I'm going to experiment a bit and try to make sure I have a good 
understanding of how this works.

Thanks again for the help.

Greg

On 11/13/2016 01:51 PM, Oliver Heger wrote:
> Hi Greg,
>
> Am 13.11.2016 um 18:41 schrieb Greg Torrance:
>> Hi Oliver,
>>
>> Thanks for the reply. That is helpful!
>>
>>> Hm, it looks as if the examples are partly incorrect. I assume that
>> the channel with id="4" should not be part of testfile1.xml, but only be
>> contained in the second file. It should appear in the results of union
>> and  merge combiner. Does that make sense?
>>
>> I'm not clear why -- if the channel with id="4" is not contained in
>> testfile1.xml -- why it will not end up in the results from all three
>> combiners. Why just union and merge and not override, too?
> On a higher level, OverrideCombiner detects that both files have a list
> of channels. Therefore, it copies the first list and ignores the second
> one. So the channels element in the first file overrides the one in the
> second file.
>
>> As for the attributes, do I understand correctly that the attribute
>> values for elements are used, essentially, as "key" values to
>> distinguish the various elements for combining purposes? And if the
>> values of any attributes of two elements differ, then the elements would
>> be considered different elements for combining purposes? (Said another
>> way, if two elements have a set of attributes in common, if the values
>> for those common attributes are the same, the elements will be
>> considered to match.) Does that make sense? Is that correct?
> This is true only for MergeCombiner. The other combiners do not try to
> match nodes in both configurations based on their attribute values; they
> take two source nodes at the same position in the hierarchy and produce
> a result node that has all the attributes of the two source nodes.
>
> Oliver
>
>> Thanks again for the reply.
>>
>> Greg
>>
>> On 11/13/2016 12:05 PM, Oliver Heger wrote:
>>> Hi Greg,
>>>
>>> Am 13.11.2016 um 15:07 schrieb Greg Torrance:
>>>> Hi all,
>>>>
>>>> I am trying to work out the precise differences between
>>>> OverrideCombiner, UnionCombiner, and MergeCombiner. However, the
>>>> examples on this page
>>>> (https://commons.apache.org/proper/commons-configuration/userguide/howto_combinedconfiguration.html)
>>>>
>>>> are confusing to me.
>>>>
>>>> testfile1.xml and testfile2.xml both contain Channels with id="4",
>>>> however none of the Combiner Results shows any Channels with id="4".
>>>> And the Notes on the right-hand side of the page contain no mention of
>>>> Channel 4.
>>>>
>>>> Am I missing something? Are the examples correct?
>>> Hm, it looks as if the examples are partly incorrect. I assume that the
>>> channel with id="4" should not be part of testfile1.xml, but only be
>>> contained in the second file. It should appear in the results of union
>>> and merge combiner. Does that make sense?
>>>
>>>> What I'm really trying to understand is the impact of attributes in the
>>>> way the various combiners choose to combine elements. (Any pointers to
>>>> further documentation on this would be appreciated.)
>>> Some more information can be found in the Javadocs of the combiner
>>> classes:
>>> - UnionCombiner states: "Another limitation is the handling of
>>> attributes: Attributes can only have a single value. So if two nodes are
>>> to be combined which both have an attribute with the same name, it is
>>> not possible to construct a proper union attribute. In this case, the
>>> attribute value from the first node is used."
>>>
>>> - OverrideCombiner has an addAttributes() method with the following
>>> documentation: "Handles the attributes during a combination process.
>>> First all attributes of the first node are added to the result. Then all
>>> attributes of the second node, which are not contained in the first
>>> node, are also added."
>>>
>>> - The merging behavior of MergeCombiner is also described in its class
>>> documentation.
>>>
>>> Does this help?
>>> Oliver
>>>
>>>> Thoughts?
>>>>
>>>> Thanks,
>>>> Greg
>>>>
>>>>
>>>> ---------------------------------------------------------------------
>>>> To unsubscribe, e-mail: user-unsubscribe@commons.apache.org
>>>> For additional commands, e-mail: user-help@commons.apache.org
>>>>
>>> ---------------------------------------------------------------------
>>> To unsubscribe, e-mail: user-unsubscribe@commons.apache.org
>>> For additional commands, e-mail: user-help@commons.apache.org
>>>
>>>
>>
>> ---------------------------------------------------------------------
>> To unsubscribe, e-mail: user-unsubscribe@commons.apache.org
>> For additional commands, e-mail: user-help@commons.apache.org
>>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: user-unsubscribe@commons.apache.org
> For additional commands, e-mail: user-help@commons.apache.org
>
>


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


Mime
View raw message