Need help in Append JSON file using ContentMerge in Apache NIFi - json

Question

I'm trying to merge a JSON file which has multiple objects. Below is my Oringinal JSON file.
{
"applicant": {
"full-name": "Tyrion Lannister",
"mobile-number" : "8435739739",
"email-id" : "tyrionlannister_casterlyrock#gmail.com"
},
"product": {
"product-category" : "Credit Card",
"product-type" : "Super Value Card - Titanium"
}
}
I will get some more JSON data as below from other source.
{
"flags": {
"duplicate-flag" : "No"
"contact-flag" : "Yes"
}
}
My task is to append the new JSON in the old JSON recods as a new object as below.
{
"applicant": {
"full-name": "Tyrion Lannister",
"mobile-number" : "8435739739",
"email-id" : "tyrionlannister_casterlyrock#gmail.com"
},
"product": {
"product-category" : "Credit Card",
"product-type" : "Super Value Card - Titanium"
},
"flags": {
"duplicate-flag" : "No"
"contact-flag" : "Yes"
}
}
Can someone help to guide, how it can be achieved in NiFi ?

Answer 1

I recommend accumulating your components as flowfile attributes, then forming a merged object with an ExecuteScript processor using JavaScript/ECMAScript. Sometimes there's just no substitute for JavaScript. Something like the following might work:
flowFile = session.get();
if (flowFile != null) {
var OutputStreamCallback = Java.type("org.apache.nifi.processor.io.OutputStreamCallback");
var StandardCharsets = Java.type("java.nio.charset.StandardCharsets");
// Get attributes
var applicant = JSON.parse(flowFile.getAttribute("applicant"));
var product = JSON.parse(flowFile.getAttribute("product"));
var flags = JSON.parse(flowFile.getAttribute("flags"));
// Combine
var merged = {
"applicant": applicant,
"product": product,
"flags": flags
};
// Write output content
flowFile = session.write(flowFile, new OutputStreamCallback(function(outputStream) {
outputStream.write(JSON.stringify(merged, null, "\t").getBytes(StandardCharsets.UTF_8));
}));
session.transfer(flowFile, REL_SUCCESS);
}