code: package io.paradoxical.cassieq.model;
  
  import com.fasterxml.jackson.core.JsonGenerator;
  import com.fasterxml.jackson.core.JsonParser;
  import com.fasterxml.jackson.core.JsonProcessingException;
  import com.fasterxml.jackson.databind.DeserializationContext;
  import com.fasterxml.jackson.databind.JsonDeserializer;
  import com.fasterxml.jackson.databind.JsonSerializer;
  import com.fasterxml.jackson.databind.SerializerProvider;
  import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
  import com.fasterxml.jackson.databind.annotation.JsonSerialize;
  import io.paradoxical.common.valuetypes.StringValue;
  import io.paradoxical.common.valuetypes.adapters.xml.JaxbStringValueAdapter;
  import jdk.nashorn.internal.ir.annotations.Immutable;
  import org.apache.commons.lang3.StringUtils;
  
  import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;
  import java.io.IOException;
  import java.util.Base64;
  import java.util.Random;
  
  @Immutable
  @XmlJavaTypeAdapter(value = MessageTag.XmlAdapter.class)
  @JsonSerialize(using = MessageTag.JsonSerializeAdapter.class)
  @JsonDeserialize(using = MessageTag.JsonDeserializeAdapater.class)
  public final class MessageTag extends StringValue {
      private static final int BYTES = 4;
  
      protected MessageTag(final String value) {
          super(value);
      }
  
      public static MessageTag valueOf(String value) {
          if (value == null) {
              return null;
          }
          return new MessageTag(StringUtils.trimToEmpty(value));
      }
  
      public static MessageTag valueOf(StringValue value) {
          if (value == null) {
              return null;
          }
          return MessageTag.valueOf(value.get());
      }
  
      public static MessageTag random() {
          Random r = new Random();
          byte[] bytes = new byte[MessageTag.BYTES];
          r.nextBytes(bytes);
  
          final String tag = Base64.getEncoder().withoutPadding().encodeToString(bytes);
          return MessageTag.valueOf(tag);
      }
  
      public static class XmlAdapter extends JaxbStringValueAdapter<MessageTag> {
          @Override
          protected MessageTag createNewInstance(String value) {
              return MessageTag.valueOf(value);
          }
      }
  
      public static class JsonDeserializeAdapater extends JsonDeserializer<MessageTag> {
  
          @Override
          public MessageTag deserialize(
                  final JsonParser jp, final DeserializationContext ctxt) throws IOException, JsonProcessingException {
              return MessageTag.valueOf(jp.getValueAsString());
          }
      }
  
      public static class JsonSerializeAdapter extends JsonSerializer<MessageTag> {
          @Override
          public void serialize(
                  final MessageTag value, final JsonGenerator jgen, final SerializerProvider provider) throws
                                                                                                       IOException,
                                                                                                       JsonProcessingException {
              jgen.writeString(value.get());
          }
      }
  }
  