java-design-patterns/layers/src/main/java/com/iluwatar/layers/app/App.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.layers.app;

import com.iluwatar.layers.dao.CakeDao;
import com.iluwatar.layers.dao.CakeLayerDao;
import com.iluwatar.layers.dao.CakeToppingDao;
import com.iluwatar.layers.dto.CakeInfo;
import com.iluwatar.layers.dto.CakeLayerInfo;
import com.iluwatar.layers.dto.CakeToppingInfo;
import com.iluwatar.layers.entity.Cake;
import com.iluwatar.layers.entity.CakeLayer;
import com.iluwatar.layers.entity.CakeTopping;
import com.iluwatar.layers.exception.CakeBakingException;
import com.iluwatar.layers.service.CakeBakingService;
import com.iluwatar.layers.service.CakeBakingServiceImpl;
import com.iluwatar.layers.view.CakeViewImpl;
import java.util.List;

/**
 * Layers is an architectural style where software responsibilities are divided among the
 * different layers of the application.
 *
 * <p>This example demonstrates a traditional 3-layer architecture consisting of data access
 * layer, business layer and presentation layer.
 *
 * <p>The data access layer is formed of Spring Data repositories <code>CakeDao</code>,
 * <code>CakeToppingDao</code> and <code>CakeLayerDao</code>. The repositories can be used
 * for CRUD operations on cakes, cake toppings and cake layers respectively.
 *
 * <p>The business layer is built on top of the data access layer. <code>CakeBakingService</code>
 * offers methods to retrieve available cake toppings and cake layers and baked cakes. Also the
 * service is used to create new cakes out of cake toppings and cake layers.
 *
 * <p>The presentation layer is built on the business layer and in this example it simply lists
 * the cakes that have been baked.
 *
 * <p>We have applied so called strict layering which means that the layers can only access the
 * classes directly beneath them. This leads the solution to create an additional set of DTOs
 * ( <code>CakeInfo</code>, <code>CakeToppingInfo</code>, <code>CakeLayerInfo</code>) to translate
 * data between layers. In other words, <code>CakeBakingService</code> cannot return entities
 * ( <code>Cake</code>, <code>CakeTopping</code>, <code>CakeLayer</code>) directly since these
 * reside on data access layer but instead translates these into business layer DTOs
 * (<code>CakeInfo</code>, <code>CakeToppingInfo</code>, <code>CakeLayerInfo</code>) and returns
 * them instead. This way the presentation layer does not have any knowledge of other layers than
 * the business layer and thus is not affected by changes to them.
 *
 * @see Cake
 * @see CakeTopping
 * @see CakeLayer
 * @see CakeDao
 * @see CakeToppingDao
 * @see CakeLayerDao
 * @see CakeBakingService
 * @see CakeInfo
 * @see CakeToppingInfo
 * @see CakeLayerInfo
 *
 */
public class App {

  private static CakeBakingService cakeBakingService = new CakeBakingServiceImpl();

  /**
   * Application entry point.
   *
   * @param args Command line parameters
   */
  public static void main(String[] args) {

    // initialize example data
    initializeData(cakeBakingService);

    // create view and render it
    var cakeView = new CakeViewImpl(cakeBakingService);
    cakeView.render();
  }

  /**
   * Initializes the example data.
   */
  private static void initializeData(CakeBakingService cakeBakingService) {
    cakeBakingService.saveNewLayer(new CakeLayerInfo("chocolate", 1200));
    cakeBakingService.saveNewLayer(new CakeLayerInfo("banana", 900));
    cakeBakingService.saveNewLayer(new CakeLayerInfo("strawberry", 950));
    cakeBakingService.saveNewLayer(new CakeLayerInfo("lemon", 950));
    cakeBakingService.saveNewLayer(new CakeLayerInfo("vanilla", 950));
    cakeBakingService.saveNewLayer(new CakeLayerInfo("strawberry", 950));

    cakeBakingService.saveNewTopping(new CakeToppingInfo("candies", 350));
    cakeBakingService.saveNewTopping(new CakeToppingInfo("cherry", 350));

    var cake1 = new CakeInfo(new CakeToppingInfo("candies", 0), List.of(
        new CakeLayerInfo("chocolate", 0),
        new CakeLayerInfo("banana", 0),
        new CakeLayerInfo("strawberry", 0)));
    try {
      cakeBakingService.bakeNewCake(cake1);
    } catch (CakeBakingException e) {
      e.printStackTrace();
    }
    var cake2 = new CakeInfo(new CakeToppingInfo("cherry", 0), List.of(
        new CakeLayerInfo("vanilla", 0),
        new CakeLayerInfo("lemon", 0),
        new CakeLayerInfo("strawberry", 0)));
    try {
      cakeBakingService.bakeNewCake(cake2);
    } catch (CakeBakingException e) {
      e.printStackTrace();
    }
  }
}