code: /*
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.skywalking.library.elasticsearch.requests.search;
  
  import com.fasterxml.jackson.core.JsonGenerator;
  import com.fasterxml.jackson.databind.JsonSerializer;
  import com.fasterxml.jackson.databind.SerializerProvider;
  import com.fasterxml.jackson.databind.annotation.JsonSerialize;
  import com.google.common.collect.ImmutableList;
  import java.io.IOException;
  import java.util.Collections;
  import java.util.Iterator;
  import lombok.AccessLevel;
  import lombok.Getter;
  import lombok.RequiredArgsConstructor;
  
  @Getter
  @JsonSerialize(using = Sorts.Serializer.class)
  @RequiredArgsConstructor(access = AccessLevel.PACKAGE)
  final class Sorts implements Iterable<Sort> {
      private final ImmutableList<Sort> sorts;
  
      @Override
      public Iterator<Sort> iterator() {
          if (sorts == null) {
              return Collections.emptyIterator();
          }
          return sorts.iterator();
      }
  
      static class Serializer extends JsonSerializer<Sorts> {
          @Override
          public void serialize(final Sorts value, final JsonGenerator gen,
                                final SerializerProvider provider)
              throws IOException {
  
              gen.writeStartArray();
              {
                  for (final Sort sort : value) {
                      gen.writeStartObject();
                      {
                          gen.writeFieldName(sort.getName());
                          gen.writeStartObject();
                          {
                              gen.writeStringField("order", sort.getOrder().toString());
                          }
                          gen.writeEndObject();
                      }
                      gen.writeEndObject();
                  }
              }
              gen.writeEndArray();
          }
      }
  }
  