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How to access the JSON fields, arrays and nested objects of JsonNode in Java?
A JsonNode is Jackson's tree model for JSON and it can read JSON into a JsonNode instance and write a JsonNode out to JSON. To read JSON into a JsonNode with Jackson by creating ObjectMapper instance and call the readValue() method. We can access a field, array or nested object using the get() method of JsonNode class. We can return a valid string representation using the asText() method and convert the value of the node to a Java int using the asInt() method of JsonNode class.
In the below example, we can access JSON fields, arrays and nested objects of JsonNode.
Example
import com.fasterxml.jackson.databind.*;
import java.io.*;
public class ParseJSONNodeTest {
public static void main(String args[]) {
String jsonStr = "{ \"name\" : \"Raja\", \"age\" : 30," +
" \"technologies\" : [\"Java\", \"Scala\", \"Python\"]," +
" \"nestedObject\" : { \"field\" : \"value\" } }";
ObjectMapper objectMapper = new ObjectMapper();
try {
JsonNode node = objectMapper.readValue(jsonStr, JsonNode.class);
JsonNode nameNode = node.get("name");
String name = nameNode.asText();
System.out.println(name);
JsonNode ageNode = node.get("age");
int age = ageNode.asInt();
System.out.println(age);
JsonNode array = node.get("technologies");
JsonNode jsonNode = array.get(1);
String techStr = jsonNode.asText();
System.out.println(techStr);
JsonNode child = node.get("nestedObject");
JsonNode childField = child.get("field");
String field = childField.asText();
System.out.println(field);
} catch (IOException e) {
e.printStackTrace();
}
}
}Output
Raja 30 Scala value
Updated on: 25-Oct-2023
27K+ Views
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