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How to read specific json node in Jackson api (tree model)?


This page shows how to read Json data in tree model using JsonNode.

Note: Refer How to convert Java object to JSON string? page for dependent libraries.

Here is the input json file:

Json Input:
{
    "emp_id": 1017,
    "emp_name": "Nagesh Y",
    "emp_designation": "Manager",
    "department": "Java2Novice",
    "salary": 30000,
    "direct_reports": [
        "Nataraj G",
        "Kalyan",
        "Mahitha"
    ]
}

package com.java2novice.json.examples;

import java.io.File;
import java.io.IOException;
import java.util.Iterator;

import org.codehaus.jackson.JsonNode;
import org.codehaus.jackson.map.ObjectMapper;

public class JsonTreeModleReadEx {

	public static void main(String a[]){
		
		ObjectMapper mapper = new ObjectMapper();
		try {
			// reading json input from the file and mapping to object
			File jsonInputFile = new File("/Users/java2novice/jsonInput.txt");
			
			JsonNode rootNode = mapper.readTree(jsonInputFile);
			// read employee id
			JsonNode empId = rootNode.path("emp_id");
			System.out.println(empId.getIntValue());
			// read employee name
			JsonNode empName = rootNode.path("emp_name");
			System.out.println(empName.getTextValue());
			// read direct reports
			JsonNode drNode = rootNode.path("direct_reports");
			Iterator<JsonNode> itr = drNode.getElements();
			System.out.println("\nDirect reports:");
			while (itr.hasNext()) {
				JsonNode temp = itr.next();
				System.out.println(temp.getTextValue());
 			}
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

Output:
1017
Nagesh Y


Direct reports:
Nataraj G
Kalyan
Mahitha
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Jackson JSON examples

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  8. How to order JSON elements using Jackson annotations?
  9. How to ignore json empty or null values using Jackson API in java?
  10. How to handle date in Json using Jackson api in java?
  11. How to read specific json node in Jackson api (tree model)?
  12. Jackson API client - how to read json from URL?
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About Author

I'm Nataraja Gootooru, programmer by profession and passionate about technologies. All examples given here are as simple as possible to help beginners. The source code is compiled and tested in my dev environment.

If you come across any mistakes or bugs, please email me to [email protected].

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Reference: Java™ Platform Standard Ed. 7 - API Specification | Java™ Platform Standard Ed. 8 - API Specification | Java is registered trademark of Oracle.
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