JAXB: Marshalling and Unmarshalling Example

Project Description

In this JAXB tutorial we will see an example on how to marshal and unmarshal Java objects.
This example explains how to,
- map Java object’s property to XML element’s attribute using @XmlAttribute annotation,
- map Java object’s property that references a class annotated with @XmlType as a child element to XML parent element.

Environment Used:

JDK 6.
Eclipse Indigo IDE for Java EE Developers.

New project in Eclipse

Create a new Java project in Eclipse IDE and name it as “SimpleJAXBDemo”.

Create Bean classes

Address.java

Create a new Class “Address.java” in the package “com.theopentutorials.jaxb.to” and copy the following code.

package com.theopentutorials.jaxb.to;

import javax.xml.bind.annotation.XmlType;

@XmlType
public class Address {
	private String street;
	private String city;
	private String state;
	private long zip;
	public String getStreet() {
		return street;
	}
	public void setStreet(String street) {
		this.street = street;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getState() {
		return state;
	}
	public void setState(String state) {
		this.state = state;
	}
	public long getZip() {
		return zip;
	}
	public void setZip(long zip) {
		this.zip = zip;
	}
	@Override
	public String toString() {
		return "Address [street=" + street + ", city=" + city + ", state="
				+ state + ", zip=" + zip + "]";
	}
}

This is a bean class which is embedded in parent class (Employee) to create a child element (<address> tag). This class is annotated with @javax.xml.bind.annotation.XmlType.

Employee.java

Create a new Class “Employee.java” in the package “com.theopentutorials.jaxb.to” and copy the following code.

package com.theopentutorials.jaxb.to;

import javax.xml.bind.annotation.XmlAccessType;
import javax.xml.bind.annotation.XmlAccessorType;
import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;

@XmlAccessorType(XmlAccessType.FIELD)
@XmlRootElement(name = "employee")
public class Employee {

	@XmlAttribute
	private int id;
	private String name;
	private String department;
	private Address address;
	
	//Must have no-argument constructor
	public Employee() {	}
	
	public Employee(int id, String name, String department, Address address) {
		super();
		this.id = id;
		this.name = name;
		this.department = department;
		this.address = address;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	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;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
	@Override
	public String toString() {
		return "Employee [id=" + id + ", name=" + name + ", department="
				+ department + ", address=" + address + "]";
	}	
}

This is the root/parent class containing JAXB annotations whose object is marshalled and unmarshalled.

@XmlAccessorType specifies whether annotations are applied to fields or Javabean properties (getters and setters).
@XmlRootElement specifies the XML element.
@XmlAttribute specifies XML element’s attribute.

Create JAXB Handler (Helper class)

Create a new Class “JAXBXMLHandler.java” in the package “com.theopentutorials.jaxb.xml” and copy the following code.

This is a helper class which has methods to perform marshalling and unmarshalling. These methods are called from client code (in this case, main() method).

Marshalling is the process of writing Java objects to XML file.
Unmarshalling is the process of converting XML content to Java objects.

package com.theopentutorials.jaxb.xml;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import javax.xml.bind.JAXBContext;
import javax.xml.bind.JAXBException;
import javax.xml.bind.Marshaller;
import javax.xml.bind.Unmarshaller;
import com.theopentutorials.jaxb.to.Employee;

public class JAXBXMLHandler {

	// Export: Marshalling
	public static void marshal(Employee employee, File selectedFile)
			throws IOException, JAXBException {
		JAXBContext context;
		BufferedWriter writer = null;
		writer = new BufferedWriter(new FileWriter(selectedFile));
		context = JAXBContext.newInstance(Employee.class);
		Marshaller m = context.createMarshaller();
		m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
		m.marshal(employee, writer);
		writer.close();
	}

	// Import: Unmarshalling
	public static Employee unmarshal(File importFile) throws JAXBException {
		Employee employee = null;
		JAXBContext context;

		context = JAXBContext.newInstance(Employee.class);
		Unmarshaller um = context.createUnmarshaller();
		employee = (Employee) um.unmarshal(importFile);

		return employee;
	}
}

Create Java Application client (main())

Create a new Class “JAXBDemo.java” in the package “com.theopentutorials.jaxb.main” and copy the following code.

package com.theopentutorials.jaxb.main;

import java.io.File;
import java.io.IOException;
import javax.xml.bind.JAXBException;
import com.theopentutorials.jaxb.to.Address;
import com.theopentutorials.jaxb.to.Employee;
import com.theopentutorials.jaxb.xml.JAXBXMLHandler;

public class JAXBDemo {
	public static void main(String[] args) {

		Address address = new Address();
		address.setStreet("2163, 1st Avenue");
		address.setCity("Peoria");
		address.setState("Illinois");
		address.setZip(61606);
		
		Employee employee = new Employee(1, "Kumar", "Development", address);
		
		try {
			//Marshalling: Writing Java object to XML file
			JAXBXMLHandler.marshal(employee, new File("employee.xml"));
		
			//Unmarshalling: Converting XML content to Java objects
			Employee employee2 = JAXBXMLHandler.unmarshal(new File("employee.xml"));
			System.out.println(employee2);	
		} catch (IOException e) {
			e.printStackTrace();
		} catch (JAXBException e) {
			e.printStackTrace();
		}		
	}
}

This class creates employee object and calls marshal method from JAXBXMLHandler helper class passing the employee object and the file to write the generated xml.
We call unmarshal method passing the marshalled file name which returns employee object.
Finally, printing the employee object (which calls toString() from Employee class).

Output

Run the JAXBDemo.java.

Employee [id=1, name=Kumar, department=Development,
address=Address [street=2163, 1st Avenue, city=Peoria, state=Illinois, zip=61606]]

Refresh your project in Project Explorer (press F5 on your project) to see the generated XML file.

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<employee id="1">
    <name>Kumar</name>
    <department>Development</department>
    <address>
        <city>Peoria</city>
        <state>Illinois</state>
        <street>2163, 1st Avenue</street>
        <zip>61606</zip>
    </address>
</employee>