Java Jackson ObjectMapper Class with Examples

The ObjectMapper class from the com.fasterxml.jackson.databind is the class that can be used to convert Java Objects (mostly POJOs) to JSON and vice-versa.

To make use of the ObjectMapper, you will need to add the jackson-databind dependency in your Gradle/Maven Project,

How to add Jackson Dependecy in Gralde Project

How to add Jackson Dependecy in Maven Project

Example: ObjectMapper to convert JSON String to Java Object

Employee.java

public class Employee {

    String empName;
    int empAge;
    String empDept;

    public  Employee() {}
    
    public Employee(String empName, int empAge, String empDept) {
        this.empName = empName;
        this.empAge = empAge;
        this.empDept = empDept;
    }

    public String getEmpName() {
        return empName;
    }

    public void setEmpName(String empName) {
        this.empName = empName;
    }

    public int getEmpAge() {
        return empAge;
    }

    public void setEmpAge(int empAge) {
        this.empAge = empAge;
    }

    public String getEmpDept() {
        return empDept;
    }

    public void setEmpDept(String empDept) {
        this.empDept = empDept;
    }
}

import com.fasterxml.jackson.databind.ObjectMapper;

public class ObjectMapperExample {

    public static void main(String[] args) {

        try {
            ObjectMapper objectMapper = new ObjectMapper();
            String employeeJson = "{ \"empName\" : \"Jake\", \"empAge\" : 35, \"empDept\" : \"Insurance\"}";

            Employee employee = objectMapper.readValue(employeeJson, Employee.class);
            System.out.println("Employee Name:" + employee.getEmpName());
            System.out.println("Employee Department:" + employee.getEmpDept());

        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Example: ObjectMapper to convert Java Object to Json String

    public static void main(String[] args) {

        try {
            Employee employee = new Employee("Jake",45,"Finance");
            ObjectMapper objectMapper = new ObjectMapper();
            String employeeJsonString = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(employee);
            System.out.println("Employee Json :" + employeeJsonString);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Output:

Employee Json :{
  "empName" : "Jake",
  "empAge" : 45,
  "empDept" : "Finance"
}