How to use of XmlGregorianCalendar with fromJson and toJson methods of gson?

Question

The theme of my project is to give XML format of data and get Json format using google-gson and I have JAXB generated java POJOs from XML schema in which I have a variable of XMLGregorianCalendar datatype.

I give the following input of XML and get the json format from the gson.toJson() method;

<?xml version="1.0" encoding="UTF-8"?>
<EmpRequest xmlns="http://java.com/Employee">
<EmplIn>
<EmpID>12</EmpID>
<Empname>sara</Empname>
<Designation>SA</Designation>
<DOJ>2002-05-30T09:30:10+06:00</DOJ>
</EmplIn>
</EmpRequest>

But in the output, I got the following.

{"emplIn":{"empID":"12","empname":"sara","designation":"SA","doj":{}}}

I surfed google and got the suggestion of adding in the xml schema and changing the XmlGregorianCalendar datatype with string. But I dont want to achieve it from both the ways.

I mean how to get the proper output with the XmlGregorianCalendar datatype through fromJson and toJson methods of gson?

Thank you so much, Harish Raj.

Solution 1

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

You could use MOXy to handle both the XML and JSON binding aspects of this use case. As I mentioned in my comment MOXy supports the XMLGregorianCalendar type. The Metadata would look like:

EmpRequest

package forum7725188;

import javax.xml.bind.annotation.*;

@XmlRootElement(name="EmpRequest")
@XmlAccessorType(XmlAccessType.FIELD)
public class EmpRequest {

    @XmlElement(name="EmplIn")
    private EmplIn emplIn;

}

EmplIn

package forum7725188;

import javax.xml.bind.annotation.*;
import javax.xml.datatype.XMLGregorianCalendar;

@XmlAccessorType(XmlAccessType.FIELD)
public class EmplIn {

    @XmlElement(name="EmpID")
    private long empId;

    @XmlElement(name="Empname")
    private String name;

    @XmlElement(name="Designation")
    private String designation;

    @XmlElement(name="DOJ")
    private XMLGregorianCalendar doj;

}

package-info

@XmlSchema(namespace="http://java.com/Employee", elementFormDefault=XmlNsForm.QUALIFIED)
@XmlAccessorType(XmlAccessType.FIELD)
package forum7725188;

import javax.xml.bind.annotation.*;

Demo

You can configure the MOXy implementation of Marshaller to output JSON by setting the eclipselink.media-type property to be application/json.

package forum7725188;

import java.io.File;   
import javax.xml.bind.*;
import javax.xml.namespace.QName;

public class Demo {

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

        Unmarshaller unmarshaller = jc.createUnmarshaller();
        File xml = new File("src/forum7725188/input.xml");
        EmpRequest empRequest = (EmpRequest) unmarshaller.unmarshal(xml);

        JAXBElement<EmpRequest> jaxbElement = new JAXBElement<EmpRequest>(new QName(""), EmpRequest.class, empRequest);
        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.setProperty("eclipselink.media-type", "application/json");
        marshaller.marshal(jaxbElement, System.out);
    }

}

input.xml

<?xml version="1.0" encoding="UTF-8"?>
<EmpRequest xmlns="http://java.com/Employee">
    <EmplIn>
        <EmpID>12</EmpID>
        <Empname>sara</Empname>
        <Designation>SA</Designation>
        <DOJ>2002-05-30T09:30:10+06:00</DOJ>
    </EmplIn>
</EmpRequest>

Output

{"EmplIn" : 
   {"EmpID" : "12",
   "Empname" : "sara",
   "Designation" : "SA",
   "DOJ" : "2002-05-30T09:30:10+06:00"}}

For More Information

• http://blog.bdoughan.com/2011/08/binding-to-json-xml-geocode-example.html
• http://blog.bdoughan.com/2011/08/json-binding-with-eclipselink-moxy.html
• http://blog.bdoughan.com/2011/05/specifying-eclipselink-moxy-as-your.html
• http://blog.bdoughan.com/2011/09/mapping-objects-to-multiple-xml-schemas.html

Solution 2

Hopefully, This can fix my issue of using google-gson.

(The following should be added in where we create the object of Gson)

Step 1:

    Gson gson =
        new GsonBuilder().registerTypeAdapter(XMLGregorianCalendar.class,
                                              new XGCalConverter.Serializer()).registerTypeAdapter(XMLGregorianCalendar.class,
                                                                                                   new XGCalConverter.Deserializer()).create();

Step 2: And we need to create the XGCalConverter Class as like the following.

 import com.google.gson.JsonDeserializationContext;
 import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonPrimitive;
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;

 import java.lang.reflect.Type;

 import javax.xml.datatype.DatatypeFactory;
 import javax.xml.datatype.XMLGregorianCalendar;

  public class XGCalConverter
  {
   public static class Serializer implements JsonSerializer
   {
    public Serializer()
    {
     super();
    }

    public JsonElement serialize(Object t, Type type,
                             JsonSerializationContext jsonSerializationContext)
    {
     XMLGregorianCalendar xgcal=(XMLGregorianCalendar)t;
     return new JsonPrimitive(xgcal.toXMLFormat());
    }
  }
    public static class Deserializer implements JsonDeserializer
    {

      public Object deserialize(JsonElement jsonElement, Type type,
                               JsonDeserializationContext jsonDeserializationContext)
      {
          try
           {
              return DatatypeFactory.newInstance().newXMLGregorianCalendar(jsonElement.getAsString());
           }
           catch(Exception ex)
           {
               ex.printStackTrace();
               return null;
           }
         }
       }
     }

Comments

[Harish Raj]

Thank you so much, Blaise. But sounds I need GAXB generated Java Pojos to be used for getting other resources of my application. Is theer any possiblity to use it with the GAXB generated Pojos?

[bdoughan]

@harish.raj - By GAXB do you mean JAXB? If so then yes. There isn't a real difference between generated classes or classes you annotate yourself as far as a JAXB runtime is concerned.

[Harish Raj]

Blaise, I use Jdeveloper. and I get the following error. Exception in thread "main" javax.xml.bind.PropertyException: name: eclipselink.media-type value: application/json at org.eclipse.persistence.jaxb.JAXBMarshaller.setProperty(JAXB‌​Marshaller.java:520) at com.moxy.employee.Test.main(Test.java:18) Can you tell me how I can install/configure EclipseLink JAXB (MOXy) so that it would be working fine.

[bdoughan]

@harish.raj - You need to use EclipseLink 2.4. You can obtain a milestone release from: eclipse.org/eclipselink/downloads/milestones.php

[Oleksi]

I am also getting this exception, but I'm using 2.4.0-SNAPSHOT. Any suggestions?

[osoblanco]

This method makes my serialized epoch times wrapped in quotes. Any ideas to get them as working numbers?