Java – NullPointerException in Avro reflectdatumwriter

I have a specific problem with Avro serialization of Java objects I have POJOs generated from the XSD schema, and then I try to use Avro serialization to place them on the Kafka topic Some xmlelements are optional

The test message is as follows:

@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 +
        '}';
  }
}

The methods for serializing and placing topics are:

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 send two fields, all work as expected If I leave one of the fields empty or missing, I get NPE from the write

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 you!

Solution

It seems that I decided to solve this problem myself after publishing, and then read the Internet a few days later

ReflectData reflectData = ReflectData.AllowNull.get();
    Schema schema = reflectData.getSchema(Testmessage.class);

    DatumWriter<Testmessage> writer = new ReflectDatumWriter<Testmessage>(schema);

It seems nice to allow null

To my next mistake! yes

org.apache.avro.UnresolvedUnionException: Not in union ["null",{"type":"record","name":"XMLGregorianCalendar","namespace":"javax.xml.datatype","fields":[]}]: 2014-10-22
at org.apache.avro.generic.GenericData.resolveUnion(GenericData.java:604)
at org.apache.avro.generic.GenericDatumWriter.resolveUnion(GenericDatumWriter.java:151)
at org.apache.avro.generic.GenericDatumWriter.write(GenericDatumWriter.java:71)
at org.apache.avro.reflect.ReflectDatumWriter.write(ReflectDatumWriter.java:143)
at org.apache.avro.generic.GenericDatumWriter.writeField(GenericDatumWriter.java:114)