71 lines
3.3 KiB
Java
71 lines
3.3 KiB
Java
/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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* <p>
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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* <p>
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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* <p>
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.dependency.injection;
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import com.google.inject.Guice;
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import com.google.inject.Injector;
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/**
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* Dependency Injection pattern deals with how objects handle their dependencies. The pattern
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* implements so called inversion of control principle. Inversion of control has two specific rules:
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* - High-level modules should not depend on low-level modules. Both should depend on abstractions.
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* - Abstractions should not depend on details. Details should depend on abstractions.
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* <p>
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* In this example we show you three different wizards. The first one ({@link SimpleWizard}) is a
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* naive implementation violating the inversion of control principle. It depends directly on a
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* concrete implementation which cannot be changed.
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* <p>
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* The second and third wizards({@link AdvancedWizard} and {@link AdvancedSorceress}) are more flexible.
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* They do not depend on any concrete implementation but abstraction. They utilizes Dependency Injection
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* pattern allowing their {@link Tobacco} dependency to be injected through constructor ({@link AdvancedWizard})
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* or setter ({@link AdvancedSorceress}). This way, handling the dependency is no longer the wizard's
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* responsibility. It is resolved outside the wizard class.
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* <p>
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* The fourth example takes the pattern a step further. It uses Guice framework for Dependency
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* Injection. {@link TobaccoModule} binds a concrete implementation to abstraction. Injector is then
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* used to create {@link GuiceWizard} object with correct dependencies.
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*/
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public class App {
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/**
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* Program entry point
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*
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* @param args command line args
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*/
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public static void main(String[] args) {
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SimpleWizard simpleWizard = new SimpleWizard();
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simpleWizard.smoke();
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AdvancedWizard advancedWizard = new AdvancedWizard(new SecondBreakfastTobacco());
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advancedWizard.smoke();
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AdvancedSorceress advancedSorceress = new AdvancedSorceress();
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advancedSorceress.setTobacco(new SecondBreakfastTobacco());
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advancedSorceress.smoke();
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Injector injector = Guice.createInjector(new TobaccoModule());
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GuiceWizard guiceWizard = injector.getInstance(GuiceWizard.class);
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guiceWizard.smoke();
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}
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}
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