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https://issues.apache.org/jira/browse/PLC4X-196?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17102904#comment-17102904
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Otto Fowler commented on PLC4X-196:
-----------------------------------
This is easy enough to add, but in looking at it, I have seen that connection
and addresses are evaluated when the processor is scheduled and re-used.
This change would mean that the connections would actually have to be created
each time and the addresses too ( although I guess you could only do that if
there were expressions present in either ).
Also, if you are going to process a lot of data, you would actually want to
re-use the connection if possible, so then you get into maybe wanting to use a
connection pool strategy.
If _just_ the addresses were to by dynamic and expression driven it would be
more simple.
Then you would have to have addresses per connection/plc/processor.
[~cdutz], do you have an opinion here?
> Apache NiFi integration should allow Expression Language
> --------------------------------------------------------
>
> Key: PLC4X-196
> URL: https://issues.apache.org/jira/browse/PLC4X-196
> Project: Apache PLC4X
> Issue Type: New Feature
> Components: Integration-NiFi
> Affects Versions: 0.7.0
> Reporter: Turker TUNALI
> Priority: Major
> Labels: feature-request
>
> Apache NiFi integration should allow us to use Expression Language for PLC
> connection string and PLC resource address string.
> We sometimes need to get data from 100 different addresses. Current
> processors doesn't allow us to create those strings on the fly. So we need to
> enter them manually or we need utilize NiFi API to create flows
> automatically.
> If those parameters allows us to use expression language, we can read a list
> from csv file or from database and then we can read them in a loop in Apache
> NiFi.
> So it will be very handy feature to dynamically specify the connection string
> and the address string.
> For starting point PutFile processor can be examined. This processor utilizes
> expression language for it's "Directory" parameter.
> [https://github.com/apache/nifi/blob/master/nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/PutFile.java]
> Notable Lines:
> import org.apache.nifi.expression.ExpressionLanguageScope;
> ...
> Define the parameter as expression language supported.
> public static final PropertyDescriptor DIRECTORY = new
> PropertyDescriptor.Builder()
> .name("Directory")
> .description("The directory to which files should be written. You may use
> expression language such as /aa/bb/${path}")
> .required(true)
> .addValidator(StandardValidators.NON_EMPTY_VALIDATOR)
> *.expressionLanguageSupported(ExpressionLanguageScope.FLOWFILE_ATTRIBUTES)*
> .build();
> ...
> And then script can be evaluated in the onTrigger event like
> context.getProperty(DIRECTORY).evaluateAttributeExpressions(flowFile).getValue()
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