How to Convert Java Object to JSON using JAXB

In this example we will see how we can convert a Java Object into an JSON using JAXB Marshalling Technique.

JAXB Dependency

We will be requiring the below jars to be put in the classpath for performing the marshalling operation.

1. jaxb-api.jar
2. org.eclipse.persistence.moxy-2.6.2.jar
3. eclipselink-2.6.2.jar
4. validation-api-1.1.0.Final.jar

Important Note : 

In order to configure MOXY as JAXB provider we need to create a file named “jaxb.properties” in the same package where the model(Student.java) exist with the below content

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

If you have missed to add the jaxb.properties file then you will be getting the below exception

javax.xml.bind.PropertyException: name: eclipselink.media-type value: application/json
	at javax.xml.bind.helpers.AbstractMarshallerImpl.setProperty(AbstractMarshallerImpl.java:358)
	at com.sun.xml.internal.bind.v2.runtime.MarshallerImpl.setProperty(MarshallerImpl.java:527)
	at com.javainterviewpoint.jaxb.Object_JSON_Example_Moxy.main(Object_JSON_Example_Moxy.java:24)

Student.java

Our Student class is a simple POJO class containing three properties name,age,id. We will be using 2 main annotations namely @XmlRootElement(Maps Class to XML element) and @XmlElement(Maps Bean property to XML element).

package com.javainterviewpoint.jaxb;

import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Student 
{
    String name;
    String age;
    int id;
    public String getName() {
        return name;
    }
    @XmlElement
    public void setName(String name) {
        this.name = name;
    }
    public String getAge() {
        return age;
    }
    @XmlElement    
    public void setAge(String age) {
        this.age = age;
    }
    public int getId() {
        return id;
    }
    @XmlElement
    public void setId(int id) {
        this.id = id;
    }
}

ObjectToJSON_Example.java

package com.javainterviewpoint.jaxb;

import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;

import org.eclipse.persistence.jaxb.MarshallerProperties;

public class ObjectToJSON_Example 
{
	public static void main(String args[])
    {
        Student st = new Student();
        st.setName("JavaInterviewPoint");
        st.setAge("11");
        st.setId(12);
        try 
        {
            //Create jaxbContext
            JAXBContext jaxbContext = JAXBContext.newInstance(Student.class);
            //Getting Marshaller object
            Marshaller jaxbMarshaller = jaxbContext.createMarshaller();
            //Setting Marshaller MediaType to json
            jaxbMarshaller.setProperty("eclipselink.media-type", "application/json");
            //set it to true for printing the root element
            jaxbMarshaller.setProperty(MarshallerProperties.JSON_INCLUDE_ROOT, true);
            //set it to true for producing a formatted output
            jaxbMarshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
            //printing the json in the console
            jaxbMarshaller.marshal(st, System.out);
        } 
        catch (JAXBException e) 
        {
            e.printStackTrace();
        }
    }
}

We will be performing the below steps to convert Object into JSON

• Create object for our Student class and set values to the property associated with it.
• JaxbContext is created by passing the class reference of the Student class.
• Call the createMarshaller() method of the context above created, to get the object of the Marshaller
• Set the Marshaller MediaType to JSON

jaxbMarshaller.setProperty("eclipselink.media-type", "application/json");

• Set MarshallerProperties.JSON_INCLUDE_ROOT as true so that the output will be including the root element and the output will be like below

{
   "student" : {
      "age" : "11",
      "id" : 12,
      "name" : "JavaInterviewPoint"
   }
}

• If MarshallerProperties.JSON_INCLUDE_ROOT is set as false, then the root element will not be included.

{
   "age" : "11",
   "id" : 12,
   "name" : "JavaInterviewPoint"
}

• Set Marshaller.JAXB_FORMATTED_OUTPUT as true, if this is not set then the output will be produced without formatting(In a single line)

{"student":{"age":"11","id":12,"name":"JavaInterviewPoint"}}

• Finally the marshal() method is called which converts the Student object into JSON.

Output :

{
   "student" : {
      "age" : "11",
      "id" : 12,
      "name" : "JavaInterviewPoint"
   }
}