Convert Java Object to JSON using Jackson

Jackson is a easy to use API that can help in the Java to/from JSON transformation.
In this post lets see how to convert java object to json using Jackson.

Add Jackson dependency

Please note we are using jackson 2 in our examples
The latest Jackson version during writing this post was 2.8.3

<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.8.3</version>
</dependency>

<groupId>com.fasterxml.jackson.core</groupId>

<artifactId>jackson-databind</artifactId>

</dependency>

If you are not using Maven you will need to download 3 jars
1. Jackson Databind 2.8.3 jar
2. Jackson Core 2.8.3 jar
3. Jackson Annotations 2.8.3 jar

Employee.java

Now lets start the example. First we will create a Employee Class

package com.kscodes.json.jackson;


public class Employee {

	private int empId;

	private String name;

	private String department;

	public Employee() {
		super();
	}

	public Employee(int empId, String name, String department) {
		super();
		this.empId = empId;
		this.name = name;
		this.department = department;
	}

	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 getDepartment() {
		return department;
	}

	public void setDepartment(String department) {
		this.department = department;
	}

}

package com.kscodes.json.jackson;

public class Employee {

private int empId;

private String name;

private String department;

public Employee() {

super();

}

public Employee(int empId, String name, String department) {

super();

this.empId = empId;

this.name = name;

this.department = department;

}

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 getDepartment() {

return department;

}

public void setDepartment(String department) {

this.department = department;

}

JavaObjectToJSON.java

Now the Class that will convert Java to JSON

package com.kscodes.json.jackson;

import java.io.File;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JavaObjectToJSON {

	public static void main(String[] args) {

		// Create a Employee Object and add data
		Employee employee = new Employee(1, "John Doe", "Sales");

		// Create an ObjectMapper object
		ObjectMapper mapper = new ObjectMapper();

		// Create file object to write JSON into
		File jsonFile = new File("C:\\kscodes\\jacksonJSONTest.json");

		try {
			mapper.writeValue(jsonFile, employee);
			System.out.println("JSON file written !!!");

		} catch (Exception e) {
			System.out.println("Exception occurred while writeing JSON File");
			System.out.println("Exception::" + e);
		}
	}

}

package com.kscodes.json.jackson;

import java.io.File;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JavaObjectToJSON {

public static void main(String[] args) {

// Create a Employee Object and add data

Employee employee = new Employee(1, "John Doe", "Sales");

// Create an ObjectMapper object

ObjectMapper mapper = new ObjectMapper();

// Create file object to write JSON into

File jsonFile = new File("C:\\kscodes\\jacksonJSONTest.json");

try {

mapper.writeValue(jsonFile, employee);

System.out.println("JSON file written !!!");

} catch (Exception e) {

System.out.println("Exception occurred while writeing JSON File");

System.out.println("Exception::" + e);

}

Output
A JSON file will be created with following data

{"empId":1,"name":"John Doe","department":"Sales"}

1	{"empId":1,"name":"John Doe","department":"Sales"}

Writing a Java List into JSON

Lets change the above code and add a List of Employee instead of a single employee. Then we will write this List into JSON and see the output

// Create a List of Employee Object and add data
List<Employee> listEmployee = new ArrayList<>();
listEmployee.add(new Employee(1, "John Doe", "Sales"));
listEmployee.add(new Employee(2, "Smith T", "Management"));
listEmployee.add(new Employee(3, "Scott Tiger", "HR"));

// Create an ObjectMapper object
ObjectMapper mapper = new ObjectMapper();

// Create file object to write JSON into
File jsonFile = new File("C:\\kscodes\\jacksonJSONTest.json");

try {
	mapper.writeValue(jsonFile, listEmployee);
	System.out.println("JSON file written !!!");

} catch (Exception e) {
	System.out.println("Exception occurred while writeing JSON File");
	System.out.println("Exception::" + e);
}

// Create a List of Employee Object and add data

List<Employee> listEmployee = new ArrayList<>();

listEmployee.add(new Employee(1, "John Doe", "Sales"));

listEmployee.add(new Employee(2, "Smith T", "Management"));

listEmployee.add(new Employee(3, "Scott Tiger", "HR"));

// Create an ObjectMapper object

ObjectMapper mapper = new ObjectMapper();

// Create file object to write JSON into

File jsonFile = new File("C:\\kscodes\\jacksonJSONTest.json");

try {

mapper.writeValue(jsonFile, listEmployee);

System.out.println("JSON file written !!!");

} catch (Exception e) {

System.out.println("Exception occurred while writeing JSON File");

System.out.println("Exception::" + e);

}

Output

[
	{"empId":1,"name":"John Doe","department":"Sales"},
	{"empId":2,"name":"Smith T","department":"Management"},
	{"empId":3,"name":"Scott Tiger","department":"HR"}
]

[

{"empId":1,"name":"John Doe","department":"Sales"},

{"empId":2,"name":"Smith T","department":"Management"},

{"empId":3,"name":"Scott Tiger","department":"HR"}

]