Convert object to/from json string in java (jackson objectmapper-example)

• Given a user defined object (POJO), we would like to convert POJO to JSON & vice versa.
• We will use jackson’s objectmapper to serialize/deserialize POJO to/from JSON.
• We will create Person class & we will perform following operations with Person class.
  • Convert Person Object (POJO) to JSON string
  • Convert JSON string to Person object (POJO)

Jackson ObjectMapper Maven Dependencies

<dependency>
 <groupId>com.fasterxml.jackson.core</groupId> 
 <artifactId>jackson-databind</artifactId>
 <version>2.7.1</version> 
</dependency>

Program – Convert object to/from json string in java

1.) Person Class:

The person class contains the data members as follows:

public class Person {
 public String firstName;
 public String lastName;
 public int age;
 public String contact;
 public Person(String firstName, String lastName,
    int age, String contact) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.age = age;
  this.contact = contact;
 }
 public String toString() {
     return "[" + firstName + " " + lastName +
         " " + age + " " +contact +"]";
 }
}

2.) JSONObjectConverter Class:

We are performing couple of operations in JSONObjectConverter class:

1. Convert Person Object (POJO) to JSON string
2. Convert JSON string to Person object (POJO)

import java.io.IOException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializationFeature;

public class JSONObjectConverter 
{
    public static void main( String[] args ) throws IOException
    {
     ObjectMapper objectMapper = new ObjectMapper();
     //Set pretty printing of json
     objectMapper.enable(SerializationFeature.INDENT_OUTPUT);
     Person objPerson = new Person("Mike", "harvey", 34, "001894536");
     
     //Convert Person object to json
     String json = objectMapper.writeValueAsString(objPerson);
     System.out.println("1. Convert Person object to Json");
     System.out.println(json);
     
     //Convert to json to person object     
     System.out.println("2. Convert JSON to person object");
     Person objFromJson = objectMapper.readValue(json, Person.class);
     System.out.println(objFromJson); 
    }
}

Output – convert object to/from json string (objectmapper)

1. Convert Person object to Json
{
  "firstName" : "Mike",
  "lastName" : "harvey",
  "age" : 34,
  "contact" : "001894536"
}
2. Convert JSON to person object
[Mike harvey 34 001894536]

Download Example Code – Jackson Object to JSON