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How to convert JSON string to Java object?


This page shows how to convert JSON string to java object using Jackson's data binding.

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

Create a simple Employee pojo. We will read JSON string from a file and map it to Employee class.

package com.java2novice.json.models;

public class Employee {

	private int empId;
	private String name;
	private String designation;
	private String department;
	private int salary;
	
	public String toString(){
		StringBuilder sb = new StringBuilder();
		sb.append("************************************");
		sb.append("\nempId: ").append(empId);
		sb.append("\nname: ").append(name);
		sb.append("\ndesignation: ").append(designation);
		sb.append("\ndepartment: ").append(department);
		sb.append("\nsalary: ").append(salary);
		sb.append("\n************************************");
		return sb.toString();
	}
	
	public int getEmpId() {
		return empId;
	}
	public void setEmpId(int empId) {
		this.empId = empId;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getDesignation() {
		return designation;
	}
	public void setDesignation(String designation) {
		this.designation = designation;
	}
	public String getDepartment() {
		return department;
	}
	public void setDepartment(String department) {
		this.department = department;
	}
	public int getSalary() {
		return salary;
	}
	public void setSalary(int salary) {
		this.salary = salary;
	}	
}

Finally here is the example to convert JSON string value to java object:

package com.java2novice.json.examples;

import java.io.File;
import java.io.IOException;

import org.codehaus.jackson.map.ObjectMapper;

import com.java2novice.json.models.Employee;

public class JsonToObject {
	
	public static void main(String a[]){
		
		ObjectMapper mapper = new ObjectMapper();
		try {
			File jsonInputFile = new File("C:\\jsonInput.txt");
			Employee emp = mapper.readValue(jsonInputFile, Employee.class);
			System.out.println(emp);
			
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}

jsonInput.txt file contains below json input:

{
    "empId": 1017,
    "name": "Nagesh Y",
    "designation": "Manager",
    "department": "Java2Novice",
    "salary": 30000
}

Output:
************************************
empId: 1017
name: Nagesh Y
designation: Manager
department: Java2Novice
salary: 30000
************************************
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Interface and its usage
Interface is similar to a class which may contain method's signature only but not bodies and it is a formal set of method and constant declarations that must be defined by the class that implements it. Interfaces are useful for declaring methods that one or more classes are expected to implement, capturing similarities between unrelated classes without forcing a class relationship and determining an object's programming interface without revealing the actual body of the class.
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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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