Jackson JSON: get node name from json-tree

Jackson JSON: get node name from json-tree

In Jackson, you can extract the node name from a JSON tree when parsing JSON data. However, JSON itself does not inherently have a concept of "node names" like XML does with element names. JSON primarily consists of key-value pairs in objects and ordered arrays of values. Nevertheless, if you have a JSON object and you want to extract the keys (which can be thought of as "node names"), you can do that using the Jackson library in Java.

Here's an example of how to extract node names (keys) from a JSON object using Jackson's JsonNode:

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonNodeExample {
    public static void main(String[] args) throws Exception {
        // Sample JSON string
        String jsonString = "{\"name\": \"John\", \"age\": 30, \"city\": \"New York\"}";

        // Create an ObjectMapper
        ObjectMapper objectMapper = new ObjectMapper();

        // Parse the JSON string into a JsonNode
        JsonNode jsonNode = objectMapper.readTree(jsonString);

        // Iterate through the fields (node names) in the JSON object
        jsonNode.fields().forEachRemaining(entry -> {
            String fieldName = entry.getKey();
            System.out.println("Node Name: " + fieldName);
        });
    }
}

In this example:

  1. We create a JSON string representing a JSON object with key-value pairs.

  2. We use the ObjectMapper class from Jackson to parse the JSON string into a JsonNode object.

  3. We iterate through the fields (key-value pairs) of the JsonNode using the fields() method, and for each field, we extract the key (which can be considered as the "node name") using entry.getKey().

  4. We print the node names to the console.

Keep in mind that this approach works for JSON objects, but it doesn't directly apply to JSON arrays or other JSON structures, which don't have "node names" in the same way objects do. In arrays, you typically access elements by index.

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