Thanks, Liam. I considered that but some of our files are rather large. It may be a short term solution, though.
From: Lee Laim <[email protected]<mailto:[email protected]>> Reply-To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Date: Monday, March 21, 2016 at 3:17 PM To: "[email protected]<mailto:[email protected]>" <[email protected]<mailto:[email protected]>> Subject: Re: Help on creating that flow that requires processing attributes in a flow content but need to preserve the original flow content 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) <[email protected]<mailto:[email protected]>> 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 <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> Reply-To: "[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>" <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> Date: Monday, March 21, 2016 at 1:58 PM To: "[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>" <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> 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) <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> 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" <[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> 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><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) ><[email protected]<mailto:[email protected]><mailto:[email protected]<mailto:[email protected]>>> > 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.
