Read elements from the Json Tree - say responseData.json

JsonNodeReadingExample1.java

String jsonString = Util.readFileFromClassPathAndConvert2String(fileNameInCP);
JsonNode root = objectMapper.readTree(jsonString);

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APPROACH-1
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JsonNode nodes = root.get("companies");
// imp note that you are going to iterate over the node values, not the keys ...
Iterator<JsonNode> itr = nodes.iterator();

while (itr.hasNext()) {
  
  JsonNode node = itr.next();
   String name =  node.get("companyname").textValue()
   // store string value or print it
}

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APPROACH-2
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Instead of iterator you can use as below

node.at("/companies").fields().forEachRemaining(e -> {
  System.out.println(e.getKey() + "---" + e.getValue().get("companyname")); 
// e.getKey() is abcd and e.getValue() is the obj, so e.getValue().get("companyname") is Hersheys
});

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APPROACH-3	
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Map<String, Object> result = objectMapper.convertValue(root, Map.class);
  for (String key : result.keySet()) {
     // this give syou ability to get the keys.. and only the keys
  }
----
  
Assume responseData.json

{
   "companies": {
       "abcd" :  {
        "companyname" : "Hersheys",
        "flavors" : {
              "xyz" : {
                  "flavorname" : "vanilla",
                   "id" : 101