Chris,
Depending on the size* of the flowfile content, a combination of
ExtractText and ReplaceText might also work.
This is what I am picturing:
ExtractText the entire contents of the flowfile into a new attribute
flowfile.original.
ReplaceText with the ${kafka.key}. This will place the ${kafka.key} into
the output stream. Then EvaluateJSONPath with the kafka.key, return
'results'.
ExtractText 'results' into another attribute, and swap the original
flowfile contents out of the attributes and back into the output stream.
*Having large flowfiles in the attribute space may not be the most
efficient for processing and provenance. You may need to adjust the
ExtractText property Max Capture Group Length (default is 1024 )to
accommodate this flow.
Thanks,
Lee
On Mon, Mar 21, 2016 at 12:38 PM, McDermott, Chris Kevin (MSDU -
STaTS/StorefrontRemote) <chris.mcderm...@hpe.com> wrote:
> Thanks everyone. While I’m naturally disappointed that this doesn’t
> exist, I am hyper charged about the responsiveness and enthusiasm of the
> NiFi community!
>
> From: Matt Burgess <mattyb...@gmail.com<mailto:mattyb...@gmail.com>>
> Reply-To: "users@nifi.apache.org<mailto:users@nifi.apache.org>" <
> users@nifi.apache.org<mailto:users@nifi.apache.org>>
> Date: Monday, March 21, 2016 at 1:58 PM
> To: "users@nifi.apache.org<mailto:users@nifi.apache.org>" <
> users@nifi.apache.org<mailto:users@nifi.apache.org>>
> Subject: Re: Help on creating that flow that requires processing
> attributes in a flow content but need to preserve the original flow content
>
> One way (in NiFi 0.5.0+) is to use the ExecuteScript processor, which
> gives you full control over the session and flowfile(s). For example if
> you had JSON in your "kafka.key" attribute such as "{"data": {"myKey":
> "myValue"}}" , you could use the following Groovy script to parse out the
> value of the 'data.myKey' field:
>
> def flowfile = session.get()
> if(!flowfile) return
> def json = new
> groovy.json.JsonSlurper().parseText(flowfile.getAttribute('kafka.key'))
> flowfile = session.putAttribute(flowfile, 'myKey', json.data.myKey)
> session.transfer(flowfile, REL_SUCCESS)
>
>
> I put an example of this up as a Gist (
> https://gist.github.com/mattyb149/478864017ec70d76f74f)
>
> A possible improvement could be to add a "jsonPath" function to Expression
> Language, which could take any value (including an attribute) along with a
> JSONPath expression to evaluate against it...
>
> Regards,
> Matt
>
> On Mon, Mar 21, 2016 at 1:48 PM, McDermott, Chris Kevin (MSDU -
> STaTS/StorefrontRemote) <chris.mcderm...@hpe.com<mailto:
> chris.mcderm...@hpe.com>> wrote:
> Joe,
>
> Thanks for the reply. I think I was not clear.
>
> The JSON I need to evaluate is in a FlowFile attribute (kafka.key) which I
> need to be able to evaluate without modifying the original FlowFile content
> (which was read from the Kafka topic). What I can’t figure out is how to
> squirrel away the flowfile content so that I can write the value of the
> kafka.key attribute to the FlowFile content, so that I can process it with
> EvaluateJsonPath, and then read content I squirreled away back into the
> FlowFile content. I considered using the the DistributedMapCache, but there
> would be no guarantee what I added to the cache would still be there when I
> needed it back.
>
>
>
>
> On 3/21/16, 1:37 PM, "Joe Witt" <joe.w...@gmail.com<mailto:
> joe.w...@gmail.com>> wrote:
>
> >Chris,
> >
> >Sounds like you have the right flow in mind already. EvaluateJSONPath
> >does not write content. It merely evaluates the given jsonpath
> >expression against the content of the flowfile and if appropriate
> >creates a flowfile attribute of what it finds.
> >
> >For example if you have JSON from Twitter you can use EvaluateJsonPath
> >and add a property with a name
> >'twitter.user' and a value of '$.user.name<http://user.name>'
> >
> >Once you run the tweets through each flow file will have an attribute
> >called 'twitter.user' with the name found in the message. No
> >manipulation of content at all. Just promotes things it finds to flow
> >file attributes.
> >
> >Thanks
> >Joe
> >
> >On Mon, Mar 21, 2016 at 1:34 PM, McDermott, Chris Kevin (MSDU -
> >STaTS/StorefrontRemote) <chris.mcderm...@hpe.com<mailto:
> chris.mcderm...@hpe.com>> wrote:
> >> What I need to do is read a file from Kafka. The Kafka key contains a
> JSON string which I need to turn in FlowFile attributes while preserving
> the original FlowFile content. Obviously I can use EvaluteJsonPath but
> that necessitates replacing the FlowFile content with the kaka.key
> attribute, thus loosing the original FlowFile content. I feel like I’m
> missing something fundamental.
>
>
