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.oap.server.core.storage.type;
  
  import java.util.Base64;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  import lombok.RequiredArgsConstructor;
  import org.apache.skywalking.oap.server.core.Const;
  import org.apache.skywalking.oap.server.library.util.CollectionUtils;
  import org.apache.skywalking.oap.server.library.util.StringUtil;
  
  /**
   * HashMapConverter represents a HashMap based converter to hold the value.
   *
   * This converter includes following converting rules.
   * 1. byte[] is converted to/from String through BASE64 encoder/decoder.
   */
  public class HashMapConverter {
      /**
       * Stateful Hashmap based converter, build object from a HashMap type source.
       */
      @RequiredArgsConstructor
      public static class ToEntity implements Convert2Entity {
          private final Map<String, Object> source;
  
          @Override
          public Object get(final String fieldName) {
              return source.get(fieldName);
          }
  
          @Override
          public byte[] getBytes(final String fieldName) {
              final String value = (String) source.get(fieldName);
              if (StringUtil.isEmpty(value)) {
                  return new byte[] {};
              }
              return Base64.getDecoder().decode(value);
          }
      }
  
      /**
       * Stateful Hashmap based converter, from object to HashMap.
       */
      public static class ToStorage implements Convert2Storage<Map<String, Object>> {
          private Map<String, Object> source;
  
          public ToStorage() {
              source = new HashMap();
          }
  
          @Override
          public void accept(final String fieldName, final Object fieldValue) {
              source.put(fieldName, fieldValue);
          }
  
          @Override
          public void accept(final String fieldName, final byte[] fieldValue) {
              if (CollectionUtils.isEmpty(fieldValue)) {
                  source.put(fieldName, Const.EMPTY_STRING);
              } else {
                  source.put(fieldName, new String(Base64.getEncoder().encode(fieldValue)));
              }
          }
  
          @Override
          public void accept(final String fieldName, final List<String> fieldValue) {
              this.accept(fieldName, (Object) fieldValue);
          }
  
          @Override
          public Object get(final String fieldName) {
              return source.get(fieldName);
          }
  
          @Override
          public Map<String, Object> obtain() {
              return source;
          }
      }
  }
  