/* * 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.dependency.injection; import com.google.inject.Guice; /** * Dependency Injection pattern deals with how objects handle their dependencies. The pattern * implements so called inversion of control principle. Inversion of control has two specific rules: * - High-level modules should not depend on low-level modules. Both should depend on abstractions. * - Abstractions should not depend on details. Details should depend on abstractions. * *

In this example we show you three different wizards. The first one ({@link SimpleWizard}) is * a naive implementation violating the inversion of control principle. It depends directly on a * concrete implementation which cannot be changed. * *

The second and third wizards({@link AdvancedWizard} and {@link AdvancedSorceress}) are more * flexible. They do not depend on any concrete implementation but abstraction. They utilizes * Dependency Injection pattern allowing their {@link Tobacco} dependency to be injected through * constructor ({@link AdvancedWizard}) or setter ({@link AdvancedSorceress}). This way, handling * the dependency is no longer the wizard's responsibility. It is resolved outside the wizard * class. * *

The fourth example takes the pattern a step further. It uses Guice framework for Dependency * Injection. {@link TobaccoModule} binds a concrete implementation to abstraction. Injector is then * used to create {@link GuiceWizard} object with correct dependencies. */ public class App { /** * Program entry point. * * @param args command line args */ public static void main(String[] args) { var simpleWizard = new SimpleWizard(); simpleWizard.smoke(); var advancedWizard = new AdvancedWizard(new SecondBreakfastTobacco()); advancedWizard.smoke(); var advancedSorceress = new AdvancedSorceress(); advancedSorceress.setTobacco(new SecondBreakfastTobacco()); advancedSorceress.smoke(); var injector = Guice.createInjector(new TobaccoModule()); var guiceWizard = injector.getInstance(GuiceWizard.class); guiceWizard.smoke(); } }