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Jul 28, 2014

Java and JAXB with MOXy implementation tutorial to convert XML to object and vice versa



Q. Why favor MOXy JAXB implementation?
A. JAXB is a specification for which there are many implementations like JDK default, MOXy, Metro, and JaxMeAPI. MOXy is from EclipseLink  enhances mapping with

1. @XmlPath extension which is inspired from XPath
2. The Jersey JAX-RS reference implementation provides JSON binding via MOXy.
3. MOXy is already the default JAXB implementation in WebLogic 12.1.1


Q. How to enable MOXy?
A.

Step 1: You need eclipselink-xxx.jar in your classpath. So, include in pom.xml dependency.

<dependency>
    <groupid>org.eclipse.persistence</groupId>
    <artifactid>eclipselink</artifactId>
    <version>2.5.1</version>
</dependency>


Step 2: You need  jaxb.properties in your classpath with the following entry.

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


Verify?

JAXBContext context = JAXBContext.newInstance(Employee.class);
System.out.println("JAXB Context is=" + context.toString());

Output:

JAXB Context is=org.eclipse.persistence.jaxb.JAXBContext@4501b7af


Now, remap Employee covered in tutorial without the nested Name object. The @XmlPath annotation from the MOXy to the rescue.


Step 1: The employee XML file

<Employee>
   <name type="first">Peter</name>
   <age>25</age>
</Employee>


Step 2: The Employee  object with annotations to map to the above XML. Note the @XmlPath annotation with XPath syntax.

package com.xml;

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlElement;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlTransient;
import javax.xml.bind.annotation.XmlType;

import org.eclipse.persistence.oxm.annotations.XmlPath;

@XmlRootElement(name = "Employee")
@XmlType(propOrder = { "name", "type", "age" })
public class Employee {

 private int id;
 private String name;
 private String type;
 private int age;

 @XmlTransient
 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 @XmlElement
 public String getName() {
  return this.name;
 }

 public void setName(String name) {
  this.name = name;
 }

 @XmlAttribute
 @XmlPath("name/@type")
 public String getType() {
  return type;
 }

 public void setType(String type) {
  this.type = type;
 }

 public int getAge() {
  return age;
 }

 public void setAge(int age) {
  this.age = age;
 }

 @Override
 public String toString() {
  StringBuilder sb = new StringBuilder();
  sb.append("name=" + this.name);
  if (type != null) {
   sb.append("\ntype=" + type);
  }
  sb.append("\n");
  sb.append("age=" + age);
  return sb.toString();
 }
}


Step 3: Marshalling and unmarshalling with MOXy.

package com.xml;

import java.io.ByteArrayInputStream;

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

public class JaxbMarshallUnMarshallWithMoxy {

 public static void main(String[] args) {

  String xml = "<Employee><name type=\"first\">Peter</name><age>25</age></Employee>";

  try {

   JAXBContext context = JAXBContext.newInstance(Employee.class);
   
   //Ensuring that we are using MOXy JAXB implementation instead of JDK default
   System.out.println("JAXB Context is=" + context.toString());

   // unmarshalling - XML to Java object
   Unmarshaller un = context.createUnmarshaller();
   Employee emp = (Employee) un.unmarshal(new ByteArrayInputStream(xml.getBytes()));

   System.out.println("Object: " + emp);

   // Marshalling - Java object to XML
   Marshaller m = context.createMarshaller();
   // for pretty-print XML in JAXB
   m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, Boolean.TRUE);
   m.marshal(emp, System.out);

  } catch (JAXBException e) {
   e.printStackTrace();
  }

 }
}


Output:

JAXB Context is=org.eclipse.persistence.jaxb.JAXBContext@4501b7af
Object: name=Peter
type=first
age=25
<?xml version="1.0" encoding="UTF-8"?>
<Employee>
   <name type="first">Peter</name>
   <age>25</age>
</Employee>

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