/** * The MIT License * Copyright (c) 2014-2016 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; import com.google.inject.Injector; /** * 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) { SimpleWizard simpleWizard = new SimpleWizard(); simpleWizard.smoke(); AdvancedWizard advancedWizard = new AdvancedWizard(new SecondBreakfastTobacco()); advancedWizard.smoke(); AdvancedSorceress advancedSorceress = new AdvancedSorceress(); advancedSorceress.setTobacco(new SecondBreakfastTobacco()); advancedSorceress.smoke(); Injector injector = Guice.createInjector(new TobaccoModule()); GuiceWizard guiceWizard = injector.getInstance(GuiceWizard.class); guiceWizard.smoke(); } }