OXM is Spring's Object/XML Mapping support which helps in conversion of Object to XML(Marshalling) and XML to Object(Unmarshalling). For this, spring has two interfaces Marshaller and Unmarshaller defined in spring-oxm under the package org.springframework.oxm.Marshaller . These can be defined as normal beans like other spring beans.
Marshaller and Unmarshaller has one method each for the actions as below.
There are different marshaller instances in spring-oxm. We will go through CastorMashaller because it's easy to implement and configure.
Code for bean "converter" is as below. Converter internally calls the marshall and unmarshall methods of CastorMarshaller.
Marshaller and Unmarshaller has one method each for the actions as below.
public interface Marshaller {
/**
* Marshals the object graph with the given root into the provided Result.
*/
void marshal(Object graph, Result result) throws XmlMappingException, IOException;
}
public interface Unmarshaller {
/**
* Unmarshals the given provided Source into an object graph.
*/
Object unmarshal(Source source) throws XmlMappingException, IOException;
}
Implementation:There are different marshaller instances in spring-oxm. We will go through CastorMashaller because it's easy to implement and configure.
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="converter" class="com.test.spring.oxm.converter.Converter"> <property name="marshaller" ref="castorMarshaller" /> <property name="unmarshaller" ref="castorMarshaller" /> </bean> <bean id="castorMarshaller" class="org.springframework.oxm.castor.CastorMarshaller"> <property name="mappingLocation" value="classpath:mapping.xml" /> </bean> </beans>CastorMarshaller is the marshaller and it requires one optional property "mappingLocation" which defines the mapping of class to xml. Sample mapping.xml file is
<?xml version="1.0" encoding="UTF-8"?> <mapping> <class name="com.test.spring.oxm.entity.Employee"> <map-to xml="employee" /> <field name="empid" type="integer"> <bind-xml name="id" node="element" /> </field> <field name="name" type="string"> <bind-xml name="ename" node="element" /> </field> <field name="dob" type="date" > <bind-xml name="dob" node="element" /> </field> <field name="salary" type="double"> <bind-xml name="salary" node="element" /> </field> </class> </mapping>Points to be noted
- property "mappingLocation" is optional. We can create CastorMarshaller without mappingLocation but it takes default values while binding
- Each class tag defines the Object which to be marshalled/unmarshalled with set of field tags. Each corresponds to XML and object mapping.
- type on the field indicates the type of the node and is mapped to Java Type.
- map-to and bind-xml tags defines the elements and attributes in the xml.
- node attribute in bind-xml defines whether the field should be attribute or element
Code for bean "converter" is as below. Converter internally calls the marshall and unmarshall methods of CastorMarshaller.
package com.test.spring.oxm.converter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import org.springframework.oxm.Marshaller;
import org.springframework.oxm.Unmarshaller;
public class Converter
{
private Marshaller marshaller;
private Unmarshaller unmarshaller;
public Marshaller getMarshaller()
{
return marshaller;
}
public void setMarshaller(Marshaller marshaller)
{
this.marshaller = marshaller;
}
public Unmarshaller getUnmarshaller()
{
return unmarshaller;
}
public void setUnmarshaller(Unmarshaller unmarshaller)
{
this.unmarshaller = unmarshaller;
}
public String convertToXml(Object obj,String filepath)
{
String finalString = new String();
FileOutputStream fos = null;
try {
fos = new FileOutputStream(filepath);
getMarshaller().marshal(obj, new StreamResult(fos));
}
catch (Exception e)
{
e.printStackTrace();
}
finally {
if(fos != null)
{
try
{
fos.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
return finalString;
}
public Object convertToObject(String filepath)
{
FileInputStream fis = null;
try {
fis = new FileInputStream(filepath);
return getUnmarshaller().unmarshal(new StreamSource(fis));
}
catch (Exception e)
{
e.printStackTrace();
}
finally {
if(fis != null)
{
try
{
fis.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
}
return null;
}
}
The object which to marshalled or unmarshalled is
package com.test.spring.oxm.entity;
import java.util.Date;
public class Employee
{
private int empid;
private String name;
private Date dob;
private Double salary;
public int getEmpid()
{
return empid;
}
public void setEmpid(int empid)
{
this.empid = empid;
}
public String getName()
{
return name;
}
public void setName(String name)
{
this.name = name;
}
public Date getDob()
{
return dob;
}
public void setDob(Date dob)
{
this.dob = dob;
}
public Double getSalary()
{
return salary;
}
public void setSalary(Double salary)
{
this.salary = salary;
}
}
Finally, the main program is
package com.test.spring.oxm;
import java.util.Date;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.test.spring.oxm.converter.Converter;
import com.test.spring.oxm.entity.Employee;
public class Application
{
public static void main(String[] args)
{
ApplicationContext context = new ClassPathXmlApplicationContext("spring-context.xml");
Converter converter = (Converter)context.getBean("converter");
Employee emp = new Employee();
emp.setDob(new Date());
emp.setEmpid(1234);
emp.setName("Employee Name");
emp.setSalary(2500.122);
converter.convertToXml(emp,"cust.xml");
Employee emp2 = (Employee)converter.convertToObject("cust.xml");
System.out.println("Empid : "+emp2.getEmpid());
System.out.println("Name : "+emp2.getName());
System.out.println("Salary: "+emp2.getSalary());
System.out.println("DOB : "+emp2.getDob());
}
}
The xml file generated out of it is :
<?xml version="1.0" encoding="UTF-8"?> <employee> <id>1234</id> <ename>Employee Name</ename> <dob>2013-07-28T21:17:29.331+05:30</dob> <salary>2500.122</salary> </employee>
