NullPointerException in Avro ReflectDatumWriter

I have a particular problem with Avro serialization of Java objects. I have a POJO generated from xsd schemas which I then try to serialize using avro to post on kafka theme. Some of the xmlElements are optional

The test message looks like this:

@XmlRootElement(name = "message")
public class Testmessage {

  @XmlElement
  public String id;


  @XmlElement
  public String name;

  public Testmessage(String id, String name) {
    this.id = id;
    this.name = name;
  }

  public Testmessage() { }

  @Override
  public String toString() {
    return "Message{" +
        "id='" + id + '\'' +
        ", name=" + name +
        '}';
  }
}

      

        
        
        
      

    

And the serialization and posting method by topic:

public void sendMessage(Testmessage msg) throws Exception{

    DatumWriter<Testmessage> writer = new ReflectDatumWriter<Testmessage>(Testmessage.class); 
    ByteArrayOutputStream os = new ByteArrayOutputStream();

    Encoder encoder = EncoderFactory.get().binaryEncoder(os, null);
    writer.write(msg, encoder);
    encoder.flush();
    os.close();
    KeyedMessage<String, byte[]> data = new KeyedMessage<String, byte[]>(TOPIC_NAME, os.toByteArray());

    producer.send(data);

}

      

        
        
        
      

    

When I submit both fields, everything works as expected. If I remove one of the fields, or leave it alone, I get the NPE from the record.

java.lang.NullPointerException: in Testmessage in string null of string in field id of    Testmessage
at org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:145)
at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:58)

      

        
        
        
      

    

Any ideas? or point me in the right direction

Thank!