Java unmarshlling XML to Object which are dynamic

Question

I\'m looking for best tool/way to create and load JAVA objects from XML definitions. I had checked out JAXB, seems pretty nice, but didn\'t find is there a way to work with

Answer 1

So, you're basically trying to make POJO's (plain old Java objects) using XML files? They are just like data classes, right?

I'm a big fan of XStream, which is really easy to use and works great if you don't need validation. I've used Castor when validation against a schema was required. I just used XStream to save an object to an xml file and then I can read it back in from anywhere, even if I change the data values associated with the object (which I think is what you mean by "dynamic set of attributes", right?).

Answer 2

Note: I'm the EclipseLink JAXB (MOXy) lead, and a member of the JAXB 2 (JSR-222) expert group.

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Check out the following EclipseLink example. It demonstrates how to use dynamic properties with both the JPA and JAXB implementations:

• http://wiki.eclipse.org/EclipseLink/Examples/MySports

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Option #1 - Static Objects with Dynamic Properties

MOXy has an @XmlVirtualAccessMethods extension which allows you to map entries in a map to XML. This allows you to add properties to a static class. In the example below the Customer class has a "real" name property and may have many "virtual" properties.

package blog.metadatasource.refresh;

import java.util.*;
import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlVirtualAccessMethods;

@XmlRootElement
@XmlType(propOrder={"firstName", "lastName", "address"})
@XmlVirtualAccessMethods
public class Customer {

    private String name;
    private Map<String, Object> extensions = new HashMap<String, Object>();

    public String getName() {
        return name;
    }

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

    public Object get(String key) {
        return extensions.get(key);
    }

    public void set(String key, Object value) {
        extensions.put(key, value);
    }

}

The virtual properties are defined via MOXy's XML metadata. In the example below we will add two properties: middleName and shippingAddress.

<?xml version="1.0"?>
<xml-bindings
    xmlns="http://www.eclipse.org/eclipselink/xsds/persistence/oxm"
    package-name="blog.metadatasource.refresh">
    <java-types>
        <java-type name="Customer">
            <java-attributes>
                <xml-element
                    java-attribute="middleName"
                    name="middle-name"
                    type="java.lang.String"/>
                <xml-element
                    java-attribute="shippingAddress"
                    name="shipping-address"
                    type="blog.metadatasource.multiple.Address"/>
            </java-attributes>
        </java-type>
    </java-types>
</xml-bindings>

For More Information

• http://blog.bdoughan.com/2011/06/extensible-models-with-eclipselink-jaxb.html
• http://blog.bdoughan.com/2011/06/moxy-extensible-models-multi-tenant.html
• http://blog.bdoughan.com/2011/06/moxy-extensible-models-multiple.html
• http://blog.bdoughan.com/2011/06/moxy-extensible-models-refresh-example.html

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Option #2 - Dynamic Objects

MOXy also offers full dynamic object models:

DynamicJAXBContext jaxbContext = DynamicJAXBContextFactory.createContextFromXSD(xsdInputStream, null, null, null);

Unmarshaller unmarshaller = jaxbContext.createUnmarshaller();
DynamicEntity customer = (DynamicEntity) unmarshaller.unmarshal(inputStream);

DynamicEntity address = jaxbContext.newDynamicEntity("org.example.Address");
address.set(street, "123 A Street");
address.set(city, "Any Town");
customer.set("address", address);

Marshaller marshaller = jaxbContext.createMarshaller();
marshaller.marshal(customer, System.out);

For More Information

• http://wiki.eclipse.org/EclipseLink/UserGuide/MOXy
• http://wiki.eclipse.org/EclipseLink/Examples/MOXy/Dynamic