Update Json field via Nifi

Question

I have a json like this coming from an input port:

{
"url": "blablabla",
"keyword": "foo"
}

then I have to generate a new json to pass to a post call. The new json is something like this:

{
    "requests": [
        {
            "source": "blablabla",
            "params": {
                "keywords": [
                    "something"
                ],
                "sub-field1": "1"
           }
        }
    ],
    "field1": "1",
    "field2": "2",
    "field3": false
}

where the array keywords should be replaced with a new array with the value of the previous Json ("foo"). The resulting is:

{
    "requests": [
        {
            "source": "blablabla",
            "params": {
                "keywords": [
                    "foo"
                ],
                "sub-field1": "1"
           }
        }
    ],
    "field1": "1",
    "field2": "2",
    "field3": false
}

then i pass this json to a invokehttp to call the post.

Could you please explain me how to generate this flow?

thanks

adhishankarit · Accepted Answer

Hi @alexmarco

If your final json format is fixed and input json also coming in same format always with values different then you extract keyword value (foo or new value) into flowfile attribute and you can use attribute in following replacetext processor to pass the value .

ExtractText processor --> UpdateAttributeProcessor --> ReplaceText Processor

1. Add a new property(keyword_value) in ExtractText and value/expression should be below

("keyword":.*)

2. Remove space,double quotes from the extracted keyword_value attribute in UpdateAttributeProcessor. (You can add the updateattribute logic directly in Replacetext processor itself for retrieving the keyword_value also as ReplaceText processor supports NiFi expression language. Its optional and you avoid Updateattribute processor in this flow then if you chose )

3. Append the keyword_value in ReplaceText processor (keep the final json ) as in sample .

4. Connect the success flow into Invokehttp processor.

* CreateKeywordvalueAttribute (Extract processor) expression below : ("keyword":.*)

* Updateattributeprocessor ${keyword_value:substringAfter(':'):trim():replace('"', '')}

* FinalReplaceText processor : Place the below JSON into Replacement Value section of the processor

{
    "requests": [
        {
            "source": "blablabla",
            "params": {
                "keywords": [
                    "${keyword_value}"
                ],
                "sub-field1": "1"
           }
        }
    ],
    "field1": "1",
    "field2": "2",
    "field3": false
}

I have attached the sample tested flow(.xml) for your reference .

Please accept the solution if it works as expected.

Thanks

Adhi

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