public class MyWarningsJsonConverter implements AttributeConverter<MyWarnings, String> {

        @Override
        public String convertToDatabaseColumn(final MyWarnings warnings) {
            if ( null != warnings && (!warnings.isEmpty()) ) {
                return JSON_CONVERTED_WARNINGS;
            }

            return null;
        }

        @Override
        public MyWarnings convertToEntityAttribute(final String dbData) {

            if (null != dbData) {
                return MODEL_FROM_JSON_OF_DBDATA;
            }
            //this executes. But gets overridden by hibernate to null
            return MyWarnings.createNew();
        }
    }

@Column(name = "warnings")
    @Convert(converter = MyWarningsJsonConverter.class)
    private MyWarnings warnings = MyWarnings.createNew();

if ( value == null || rs.wasNull() ) {  //rs resultset
        return null;
    }