java-design-patterns/partial-response/src/main/java/com/iluwatar/partialresponse/FieldJsonMapper.java

/*
 * The MIT License
 * Copyright © 2014-2019 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package com.iluwatar.partialresponse;

import java.lang.reflect.Field;

/**
 * Map a video to json.
 */
public class FieldJsonMapper {

  /**
   * Gets json of required fields from video.
   *
   * @param video  object containing video information
   * @param fields fields information to get
   * @return json of required fields from video
   */
  public String toJson(Video video, String[] fields) throws Exception {
    var json = new StringBuilder().append("{");

    var i = 0;
    var fieldsLength = fields.length;
    while (i < fieldsLength) {
      json.append(getString(video, Video.class.getDeclaredField(fields[i])));
      if (i != fieldsLength - 1) {
        json.append(",");
      }
      i++;
    }
    json.append("}");
    return json.toString();
  }

  private String getString(Video video, Field declaredField) throws IllegalAccessException {
    declaredField.setAccessible(true);
    var value = declaredField.get(video);
    if (declaredField.get(video) instanceof Integer) {
      return "\"" + declaredField.getName() + "\"" + ": " + value;
    }
    return "\"" + declaredField.getName() + "\"" + ": " + "\"" + value.toString() + "\"";
  }
}