JSON, or JavaScript Object Notation, serves as a widely adopted data exchange format due to its simplicity and ease of use. However, when dealing with JSON in a language like Java, where objects are omnipresent, the relevance of JSON nodes becomes apparent. Why use JSON nodes in Java when objects can seemingly handle everything? The answer lies in scenarios where a JSON node lacks a predefined structure, yet you need to manipulate a part of it while preserving the integrity of the whole. This is precisely where the significance of JSON nodes in Java emerges.

Utilizing JSON Nodes in Java

Let's delve into the process of converting a JSON string into a JSON node using the Jackson library in Java:

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

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

        // Parse JSON string into JsonNode
        ObjectMapper objectMapper = new ObjectMapper();
        JsonNode jsonNode = objectMapper.readTree(jsonString);
    }
}

The objectMapper.readTree(string) method efficiently converts the JSON string into a JsonNode, providing a foundation for further exploration and manipulation.

Extracting and Displaying Values

Now, let's extract specific values from the JSON node and display them:

// Accessing values from JsonNode
String name = jsonNode.get("name").asText();
int age = jsonNode.get("age").asInt();

// Displaying values
System.out.println("Name: " + name);
System.out.println("Age: " + age);

In this snippet, jsonNode.get(fieldName).asText() retrieves values as text, and asInt() converts values to integers. The flexibility of Jackson allows similar methods for handling double, boolean, and other data types.

Dynamic Manipulation with JsonNode

Now, let's explore how to dynamically manipulate a JSON node by adding a new field, "occupation," and assigning it the value "Player":

System.out.print(jsonNode);
((ObjectNode) jsonNode).set("occupation", objectMapper.readTree("\"Player\""));
System.out.print(jsonNode);

In this example, we use ObjectNode, a subset of JsonNode, for manipulation, as JsonNode itself lacks direct methods for modification. The syntax objectNode.set(fieldName, jsonNode) allows us to add and modify fields dynamically. The objectMapper.readTree method assists in creating a JsonNode, as discussed earlier.

Try It Yourself

Try adding an address nested object with first line second line and third line

Conclusion:

In summary, leveraging JsonNode in Java provides a powerful and flexible approach to handle JSON data dynamically. This not only facilitates the conversion of JSON strings into a structured format but also enables seamless extraction, manipulation, and addition of fields. Jackson's ObjectNode proves to be a valuable tool for dynamic JSON manipulation in scenarios where the structure may vary or needs modification. Cheers to enhancing your Java JSON manipulation skills!