Converting Nested json into dot notation json

Question

I have a service from where I get a json string response like as shown below

{
  \"id\": \"123\",
  \"name\": \"John\"
}

I consume the rest

Answer 1

Here is a recursive method that will flatten a nested Map with any depth to the desired dot notation. You can pass it to Jackson's ObjectMapper to get the desired json output:

@SuppressWarnings("unchecked")
public static Map flatMap(String parentKey, Map nestedMap)
{
    Map flatMap = new HashMap<>();
    String prefixKey = parentKey != null ? parentKey + "." : "";
    for (Map.Entry entry : nestedMap.entrySet()) {
        if (entry.getValue() instanceof String) {
            flatMap.put(prefixKey + entry.getKey(), (String)entry.getValue());
        }
        if (entry.getValue() instanceof Map) {
            flatMap.putAll(flatMap(prefixKey + entry.getKey(), (Map)entry.getValue()));
        }
    }
    return flatMap;
}

Usage:

mapper.writeValue(System.out, flatMap(null, nestedMap));