Joseph Witt created NIFI-1249:
---------------------------------
Summary: Allow ReplaceText expression language functions to access
matching group values
Key: NIFI-1249
URL: https://issues.apache.org/jira/browse/NIFI-1249
Project: Apache NiFi
Issue Type: Improvement
Components: Extensions
Reporter: Joseph Witt
Chanru from the user's mailing list asked how we'd support a pretty simple use
case of converting
{quote}
col1,col2,col3
2006,10-01-2004,10may2004
2007,15-05-2006,10jun2005
2009,8-8-2008,10aug2008
{quote}
to this
{quote}
col1,col2,col3
2006,10-01-2004,2004-05-10
2007,15-05-2006,2005-06-10
2009,8-8-2008,2008-08-10
{quote}
And we can do it today but it is surprising more effort than it should be. The
problem is that ReplaceText as-is gets us sooo close. But what it cannot do is
convert the original column three into a formatted Date object which can then
be written out as a formatted string. If it could then this would be easy. So
for example if we extracted each column as a matching group and the replacement
value could be
{quote}
${ $3:toDate('ddMMMyyy'):format('yyyy/MM/ddd')}
{quote}
Then we'd be all set. But right now there is no way to take that third
matching group and do anything fun with expression language on it because it is
not a subject passed into the EL on which functions could be applied. If
instead we simply added those matching groups as keys/subjects available to the
EL then this becomes a quite powerful tool.
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