Question

I am looking for a Java library to convert my domain objects into a flattened JSON

eg.

public class Person {
   String name
   Address homeAddress
}

public class Address {
  String street
  String zip
}

JSON: {name:'John', homeAddress_street: '123 Street', homeAddress_zip: 'xxxxx'}

I’ve looked into XStream, Eclipse MOXy, FlexJSON, JSON-lib & gson

My goal is to get rid of my json wrapper classes and minimize code. I would like to have a general service that would take any domain model class I have and get a json representation without having to write xml descriptors or any custom converters for each type of model. A depth of 1 level deep is sufficient for my models. I have not found an easy generic solution using annotations or built in functionality in the above libraries but I have probably overlooked them. Is there a non intrusive library that can do this? or maybe one that I’ve listed? I’m using Hibernate so the library must be able to deal with CGLib Proxies

Answer 1

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

Below is an example of how this could be done with MOXy by leveraging the @XmlPath extension.

Person

package forum7652387;

import javax.xml.bind.annotation.*;
import org.eclipse.persistence.oxm.annotations.XmlPath;

@XmlAccessorType(XmlAccessType.FIELD)
public class Person {
    String name;

    @XmlPath(".")
    Address homeAddress;
}

Address

package forum7652387;

import javax.xml.bind.annotation.*;

@XmlAccessorType(XmlAccessType.FIELD)
public class Address {
    @XmlElement(name="homeAddress_street")
    String street;

    @XmlElement(name="homeAddress_zip")
    String zip;
}

jaxb.properties

To specify MOXy as your JAXB provider you need to add a file called jaxb.properties in the same package as your domain classes with the following entry:

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

Demo

package forum7652387;

import java.io.StringReader;
import javax.xml.bind.*;
import javax.xml.transform.stream.StreamSource;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Person.class);

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        unmarshaller.setProperty("eclipselink.media-type", "application/json");
        unmarshaller.setProperty("eclipselink.json.include-root", false);
        String jsonString = "{\"name\":\"John\", \"homeAddress_street\":\"123 Street\", \"homeAddress_zip\":\"xxxxx\"}";
        StreamSource jsonSource = new StreamSource(new StringReader(jsonString));
        Person person = unmarshaller.unmarshal(jsonSource, Person.class).getValue();

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty("eclipselink.media-type", "application/json");
        marshaller.setProperty("eclipselink.json.include-root", false);
        marshaller.marshal(person, System.out);
    }

}

Output

 {"name" : "John", "homeAddress_street" : "123 Street", "homeAddress_zip" : "xxxxx"}

For More Information

• http://blog.bdoughan.com/2011/08/json-binding-with-eclipselink-moxy.html