The JAXB Unmarshaller
interface is responsible for governing the process of deserializing the XML data to Java Objects. The unmarshalling to objects can be done to variety of input sources.
1. How to unmarshal XML to Object
1.1. Create Unmarshaller
Generally, to create Unmarshaller you can reuse this code.
JAXBContext jaxbContext = JAXBContext.newInstance( Employee.class ); Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller(); //Overloaded methods to unmarshal from different xml sources Employee employee = (Employee) jaxbUnmarshaller.unmarshal( xmlSource );
1.2. Unmarshalling from an InputStream
InputStream inStream = new FileInputStream( "employee.xml" ); Employee employee = (Employee) jaxbUnmarshaller.unmarshal( inStream );
1.3. Unmarshalling from a URL
URL url = new URL( "http://localhost:8080/employee.xml" ); Employee employee = (Employee) jaxbUnmarshaller.unmarshal( url );
1.4. Unmarshalling the String content
String xmlString = "..."; Employee employee = (Employee) jaxbUnmarshaller.unmarshal(new StringReader(xmlString));
1.5. Unmarshalling from a org.w3c.dom.Node
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); dbf.setNamespaceAware(true); DocumentBuilder db = dbf.newDocumentBuilder(); Document document = db.parse(new File( "employee.xml")); //Node Employee employee = (Employee) jaxbUnmarshaller.unmarshal( document );
2. JAXB Unmarshaller Properties
There currently are not any properties required to be supported by all JAXB Providers on Unmarshaller. However, some providers may support their own set of provider specific properties.
3. Unmarshaller Event Callbacks
You can customize the Unmarshalling operation by adding these callback methods inside JAXB annotated class e.g. Employee.java
. You need to define two methods which will listen before and after the Unmarshaller
process that class.
void beforeUnmarshal(Unmarshaller unmarshaller, Object parent) {}
void afterUnmarshal(Unmarshaller unmarshaller, Object parent) {}
package com.howtodoinjava.demo.model; import java.io.Serializable; import javax.xml.bind.Marshaller; import javax.xml.bind.annotation.XmlAccessType; import javax.xml.bind.annotation.XmlAccessorType; import javax.xml.bind.annotation.XmlRootElement; @XmlRootElement(name = "employee") @XmlAccessorType(XmlAccessType.PROPERTY) public class Employee implements Serializable { private static final long serialVersionUID = 1L; private Integer id; private String firstName; private String lastName; private Department department; public Employee() { super(); } //Setters and Getters @Override public String toString() { return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", department=" + department + "]"; } // It is called immediately after the object is created and before the unmarshalling begins. // The callback provides an opportunity to initialize JavaBean properties prior to unmarshalling. void beforeUnmarshal(Unmarshaller unmarshaller, Object parent) { System.out.println("Before Unmarshaller Callback"); } // It is called after all the properties are unmarshalled for this object, // but before this object is set to the parent object. void afterUnmarshal(Unmarshaller unmarshaller, Object parent) { System.out.println("After Unmarshaller Callback"); } }
4. JAXB Unmarshaller Example
Example of unmarshalling XML file to Java Object.
package com.howtodoinjava.demo; import java.io.File; import javax.xml.bind.JAXBContext; import javax.xml.bind.JAXBException; import javax.xml.bind.Unmarshaller; import com.howtodoinjava.demo.model.Employee; public class JaxbExample { public static void main(String[] args) { String fileName = "employee.xml"; jaxbXmlFileToObject(fileName); } private static void jaxbXmlFileToObject(String fileName) { File xmlFile = new File(fileName); JAXBContext jaxbContext; try { jaxbContext = JAXBContext.newInstance(Employee.class); Unmarshaller jaxbUnmarshaller = jaxbContext.createUnmarshaller(); Employee employee = (Employee) jaxbUnmarshaller.unmarshal(xmlFile); System.out.println(employee); } catch (JAXBException e) { e.printStackTrace(); } } }
Program Output.
Before Unmarshaller Callback After Unmarshaller Callback Employee [id=1, firstName=Lokesh, lastName=Gupta, department=Department [id=101, name=IT]]
Where employee.xml
file is:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <employee> <department> <id>101</id> <name>IT</name> </department> <firstName>Lokesh</firstName> <id>1</id> <lastName>Gupta</lastName> </employee>
Drop me your questions in comments section related to unmarshalling in java using jaxb.
Happy Learning !!
rathore
my Xml root element has an attribute the how to handle while unmarshalling..
swetanand singh
The example given above is not working. After unmarshalling all the fields are zero.
Suresh A K
check whether you created a Department Entity class
anonymous
if overriding of unmarshalling happens .how to resolve ?
like if i have 2 JAXB resposnes like
InputStream inStream = new FileInputStream( “employee.xml” );
Employee employee = (Employee) jaxbUnmarshaller.unmarshal( inStream );
InputStream inStream2 = new FileInputStream( “studentxml” );
Employee employee = (Employee) jaxbUnmarshaller.unmarshal( inStream );
if i did i am getting instream2 response as instream response .how to resolve this type of issues ?
Moe
Hi,
So after the unmarshalling if I want to turn the pojo into a json object to pass to the server, how would I do that?
Jamal
could you please tell me from where employee.xml is there i mean your reading from resource path or any other path,please give me some examples how to read xml from resource path.