本篇文章代码：https://gitee.com/bithachi_admin_admin/mycode/tree/master/%E8%AE%BE%E8%AE%A1%E6%A8%A1%E5%BC%8F/factory

一、工厂模式

1. 什么是工厂模式？

• 工厂模式（Factory Pattern）提供了一种创建对象的最佳方式，是 Java 中最常用的设计模式之一。这种类型的设计模式属于创建型模式。
• 在工厂模式中，我们在创建对象时不会对客户端暴露创建逻辑，并且是通过使用一个共同的接口来指向新创建的对象。

**意图：**定义一个创建对象的接口，让其子类自己决定实例化哪一个工厂类，工厂模式使其创建过程延迟到子类进行。(依赖倒置原则)

**主要解决：**主要解决接口选择的问题。

**何时使用：**我们明确地计划不同条件下创建不同实例时。

**如何解决：**让其子类实现工厂接口，返回的也是一个抽象的产品。

**关键代码：**创建过程在其子类执行。

应用实例：

• 您需要一辆汽车，可以直接从工厂里面提货，而不用去管这辆汽车是怎么做出来的，以及这个汽车里面的具体实现。
• Mybatis换数据库只需换方言和驱动就可以。

优点：

• 一个调用者想创建一个对象，只要知道其名称就可以了。
• 扩展性高，如果想增加一个产品，只要扩展一个工厂类就可以。
• 屏蔽产品的具体实现，调用者只关心产品的接口。

**缺点：**每次增加一个产品时，都需要增加一个具体类和对象实现工厂，使得系统中类的个数成倍增加，在一定程度上增加了系统的复杂度，同时也增加了系统具体类的依赖。这并不是什么好事。

使用场景：

• 日志记录器：记录可能记录到本地硬盘、系统事件、远程服务器等，用户可以选择记录日志到什么地方。
• 数据库访问，当用户不知道最后系统采用哪一类数据库，以及数据库可能有变化时。
• 设计一个连接服务器的框架，需要三个协议，“POP3”、“IMAP”、“HTTP”，可以把这三个作为产品类，共同实现一个接口。

**注意事项：**作为一种创建类模式，在任何需要生成复杂对象的地方，都可以使用工厂方法模式。有一点需要注意的地方就是复杂对象适合使用工厂模式，而简单对象，特别是只需要通过 new 就可以完成创建的对象，无需使用工厂模式。如果使用工厂模式，就需要引入一个工厂类，会增加系统的复杂度。

2. 加盟披萨店案例

案例描述：你有一家披萨店，经营有成，击败了许多的竞争者，现在你想开扩大市场，建立加盟店。因为区域的差异，每家加盟店都可能想要提供不同风味的比萨(比方说纽约、芝加哥、加州)，这受到了开店地点及该地区比萨美食家口味的影响。那么如何设计呢？

下面是案例的UML模型设计图：

PizzaStore：

public abstract class PizzaStore {abstract Pizza createPizza(String item);public Pizza orderPizza(String type) {Pizza pizza = createPizza(type);System.out.println("--- Making a " + pizza.getName() + " ---");pizza.prepare();pizza.bake();pizza.cut();pizza.box();return pizza;}
}

NYPizzaStore:

public class NYPizzaStore extends PizzaStore {@OverridePizza createPizza(String item) {if (item.equals("cheese")) {return new NYStyleCheesePizza();} else if (item.equals("veggie")) {return new NYStyleVeggiePizza();} else if (item.equals("clam")) {return new NYStyleClamPizza();} else if (item.equals("pepperoni")) {return new NYStylePepperoniPizza();} else {return null;}}
}

Pizza:

import java.util.ArrayList;
public abstract class Pizza {String name;String dough;String sauce;ArrayList<String> toppings = new ArrayList<String>();void prepare() {System.out.println("Prepare " + name);System.out.println("Tossing dough...");System.out.println("Adding sauce...");System.out.println("Adding toppings: ");for (String topping : toppings) {System.out.println("   " + topping);}}void bake() {System.out.println("Bake for 25 minutes at 350");}void cut() {System.out.println("Cut the pizza into diagonal slices");}void box() {System.out.println("Place pizza in official PizzaStore box");}public String getName() {return name;}@Overridepublic String toString() {StringBuffer display = new StringBuffer();display.append("---- " + name + " ----\n");display.append(dough + "\n");display.append(sauce + "\n");for (String topping : toppings) {display.append(topping + "\n");}return display.toString();}
}

NYStyleCheesePizza**：**

public class NYStyleCheesePizza extends Pizza {public NYStyleCheesePizza() { name = "NY Style Sauce and Cheese Pizza";dough = "Thin Crust Dough";sauce = "Marinara Sauce";toppings.add("Grated Reggiano Cheese");}
}

披萨店测试：

public class PizzaTestDrive {public static void main(String[] args) {PizzaStore nyStore = new NYPizzaStore();PizzaStore chicagoStore = new ChicagoPizzaStore();Pizza pizza = nyStore.orderPizza("cheese");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("cheese");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("clam");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("clam");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("pepperoni");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("pepperoni");System.out.println("Joel ordered a " + pizza.getName() + "\n");pizza = nyStore.orderPizza("veggie");System.out.println("Ethan ordered a " + pizza.getName() + "\n");pizza = chicagoStore.orderPizza("veggie");System.out.println("Joel ordered a " + pizza.getName() + "\n");}
}

运行结果：

--- Making a NY Style Sauce and Cheese Pizza ---
Prepare NY Style Sauce and Cheese Pizza
Tossing dough...
Adding sauce...
Adding toppings: Grated Reggiano Cheese
Bake for 25 minutes at 350
Cut the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a NY Style Sauce and Cheese Pizza--- Making a Chicago Style Deep Dish Cheese Pizza ---
Prepare Chicago Style Deep Dish Cheese Pizza
Tossing dough...
Adding sauce...
Adding toppings: Shredded Mozzarella Cheese
Bake for 25 minutes at 350
Cutting the pizza into square slices
Place pizza in official PizzaStore box
Joel ordered a Chicago Style Deep Dish Cheese Pizza--- Making a NY Style Clam Pizza ---
Prepare NY Style Clam Pizza
Tossing dough...
Adding sauce...
Adding toppings: Grated Reggiano CheeseFresh Clams from Long Island Sound
Bake for 25 minutes at 350
Cut the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a NY Style Clam Pizza--- Making a Chicago Style Clam Pizza ---
Prepare Chicago Style Clam Pizza
Tossing dough...
Adding sauce...
Adding toppings: Shredded Mozzarella CheeseFrozen Clams from Chesapeake Bay
Bake for 25 minutes at 350
Cutting the pizza into square slices
Place pizza in official PizzaStore box
Joel ordered a Chicago Style Clam Pizza--- Making a NY Style Pepperoni Pizza ---
Prepare NY Style Pepperoni Pizza
Tossing dough...
Adding sauce...
Adding toppings: Grated Reggiano CheeseSliced PepperoniGarlicOnionMushroomsRed Pepper
Bake for 25 minutes at 350
Cut the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a NY Style Pepperoni Pizza--- Making a Chicago Style Pepperoni Pizza ---
Prepare Chicago Style Pepperoni Pizza
Tossing dough...
Adding sauce...
Adding toppings: Shredded Mozzarella CheeseBlack OlivesSpinachEggplantSliced Pepperoni
Bake for 25 minutes at 350
Cutting the pizza into square slices
Place pizza in official PizzaStore box
Joel ordered a Chicago Style Pepperoni Pizza--- Making a NY Style Veggie Pizza ---
Prepare NY Style Veggie Pizza
Tossing dough...
Adding sauce...
Adding toppings: Grated Reggiano CheeseGarlicOnionMushroomsRed Pepper
Bake for 25 minutes at 350
Cut the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a NY Style Veggie Pizza--- Making a Chicago Deep Dish Veggie Pizza ---
Prepare Chicago Deep Dish Veggie Pizza
Tossing dough...
Adding sauce...
Adding toppings: Shredded Mozzarella CheeseBlack OlivesSpinachEggplant
Bake for 25 minutes at 350
Cutting the pizza into square slices
Place pizza in official PizzaStore box
Joel ordered a Chicago Deep Dish Veggie Pizza进程已结束,退出代码0

二、抽象工程模式

1. 什么是抽象工厂模式？

• 抽象工厂模式（Abstract Factory Pattern）是围绕一个超级工厂创建其他工厂。该超级工厂为其他工厂的父工厂。这种类型的设计模式属于创建型模式，它提供了一种创建对象的最佳方式。
• 在抽象工厂模式中，接口是负责创建一个相关对象的工厂，不需要显式指定它们的类。每个生成的工厂都能按照工厂模式提供对象。

**意图：**提供一个创建一系列相关或相互依赖对象的接口，而无需指定它们具体的类。

**主要解决：**主要解决接口选择的问题。

**何时使用：**系统的产品有多于一个的产品族，而系统只消费其中某一族的产品。

**如何解决：**在一个产品族里面，定义多个产品。

**关键代码：**在一个工厂里聚合多个同类产品。

**应用实例：**工作了，为了参加一些聚会，肯定有两套或多套衣服吧，比如说有商务装（成套，一系列具体产品）、时尚装（成套，一系列具体产品），甚至对于一个家庭来说，可能有商务女装、商务男装、时尚女装、时尚男装，这些也都是成套的，即一系列具体产品。假设一种情况，在您的家中，某一个衣柜（具体工厂）只能存放某一种这样的衣服（成套，一系列具体产品），每次拿这种成套的衣服时也自然要从这个衣柜中取出了。用 OOP 的思想去理解，所有的衣柜（具体工厂）都是衣柜类的（抽象工厂）某一个，而每一件成套的衣服又包括具体的上衣（某一具体产品），裤子（某一具体产品），这些具体的上衣其实也都是上衣（抽象产品），具体的裤子也都是裤子（另一个抽象产品）。

**优点：**当一个产品族中的多个对象被设计成一起工作时，它能保证客户端始终只使用同一个产品族中的对象。

**缺点：**产品族扩展非常困难，要增加一个系列的某一产品，既要在抽象的 Creator 里加代码，又要在具体的里面加代码。

使用场景： 1、QQ 换皮肤，一整套一起换。 2、生成不同操作系统的程序。

**注意事项：**产品族难扩展，产品等级易扩展。

2. 给加盟披萨店新增原料工厂

案例描述：你有一家披萨店，经营有成，击败了许多的竞争者，现在你想开扩大市场，建立加盟店。因为区域的差异，每家加盟店都可能想要提供不同风味的比萨(比方说纽约、芝加哥、加州)，这受到了开店地点及该地区比萨美食家口味的影响。那么如何设计呢？这是我们工厂模式的案例，现在我们在此案例上加点东西，我们希望所有的加盟店都使用统一的调料(原料)：面团、酱料、腊肠、芝士、蔬菜、肉等。我们可以建造原料工厂来满足这种需求。

下面是UML设计模型：

下面给出核心实现代码;

**
**

披萨抽象类Pizza：

public abstract class Pizza {String name;Dough dough;Sauce sauce;Veggies veggies[];Cheese cheese;Pepperoni pepperoni;Clams clam;abstract void prepare();void bake() {System.out.println("Bake for 25 minutes at 350");}void cut() {System.out.println("Cutting the pizza into diagonal slices");}void box() {System.out.println("Place pizza in official PizzaStore box");}void setName(String name) {this.name = name;}String getName() {return name;}@Overridepublic String toString() {StringBuffer result = new StringBuffer();result.append("---- " + name + " ----\n");if (dough != null) {result.append(dough);result.append("\n");}if (sauce != null) {result.append(sauce);result.append("\n");}if (cheese != null) {result.append(cheese);result.append("\n");}if (veggies != null) {for (int i = 0; i < veggies.length; i++) {result.append(veggies[i]);if (i < veggies.length-1) {result.append(", ");}}result.append("\n");}if (clam != null) {result.append(clam);result.append("\n");}if (pepperoni != null) {result.append(pepperoni);result.append("\n");}return result.toString();}
}

具体的某种披萨类CheesePizza:

public class CheesePizza extends Pizza {//原料工厂PizzaIngredientFactory ingredientFactory;public CheesePizza(PizzaIngredientFactory ingredientFactory) {this.ingredientFactory = ingredientFactory;}@Overridevoid prepare() {System.out.println("Preparing " + name);dough = ingredientFactory.createDough();sauce = ingredientFactory.createSauce();cheese = ingredientFactory.createCheese();}
}

披萨店抽象类PizzaStore:

public abstract class PizzaStore {protected abstract Pizza createPizza(String item);public Pizza orderPizza(String type) {Pizza pizza = createPizza(type);System.out.println("--- Making a " + pizza.getName() + " ---");pizza.prepare();pizza.bake();pizza.cut();pizza.box();return pizza;}
}

纽约披萨店NYPizzaStore:

**
**

public class NYPizzaStore extends PizzaStore {@Overrideprotected Pizza createPizza(String item) {Pizza pizza = null;PizzaIngredientFactory ingredientFactory =  new NYPizzaIngredientFactory();if (item.equals("cheese")) {pizza = new CheesePizza(ingredientFactory);pizza.setName("New York Style Cheese Pizza");} else if (item.equals("veggie")) {pizza = new VeggiePizza(ingredientFactory);pizza.setName("New York Style Veggie Pizza");} else if (item.equals("clam")) {pizza = new ClamPizza(ingredientFactory);pizza.setName("New York Style Clam Pizza");} else if (item.equals("pepperoni")) {pizza = new PepperoniPizza(ingredientFactory);pizza.setName("New York Style Pepperoni Pizza");} return pizza;}
}

原料工厂抽象类****PizzaIngredientFactory：

public interface PizzaIngredientFactory {public Dough createDough();public Sauce createSauce();public Cheese createCheese();public Veggies[] createVeggies();public Pepperoni createPepperoni();public Clams createClam();
}

具体的纽约原料工厂****NYPizzaIngredientFactory：

public class NYPizzaIngredientFactory implements PizzaIngredientFactory {@Overridepublic Dough createDough() {return new ThinCrustDough();}@Overridepublic Sauce createSauce() {return new MarinaraSauce();}@Overridepublic Cheese createCheese() {return new ReggianoCheese();}@Overridepublic Veggies[] createVeggies() {Veggies veggies[] = { new Garlic(), new Onion(), new Mushroom(), new RedPepper() };return veggies;}@Overridepublic Pepperoni createPepperoni() {return new SlicedPepperoni();}@Overridepublic Clams createClam() {return new FreshClams();}
}

某类型的具体原料产品****Mushroom：

public class Mushroom implements Veggies {@Overridepublic String toString() {return "Mushrooms";}
}

测试运行PizzaTestDrive：

public class PizzaTestDrive {public static void main(String[] args) {PizzaStore nyStore = new NYPizzaStore();PizzaStore chicagoStore = new ChicagoPizzaStore();Pizza pizza = nyStore.orderPizza("cheese");System.out.println("Ethan ordered a " + pizza + "\n");pizza = chicagoStore.orderPizza("cheese");System.out.println("Joel ordered a " + pizza + "\n");pizza = nyStore.orderPizza("clam");System.out.println("Ethan ordered a " + pizza + "\n");pizza = chicagoStore.orderPizza("clam");System.out.println("Joel ordered a " + pizza + "\n");pizza = nyStore.orderPizza("pepperoni");System.out.println("Ethan ordered a " + pizza + "\n");pizza = chicagoStore.orderPizza("pepperoni");System.out.println("Joel ordered a " + pizza + "\n");pizza = nyStore.orderPizza("veggie");System.out.println("Ethan ordered a " + pizza + "\n");pizza = chicagoStore.orderPizza("veggie");System.out.println("Joel ordered a " + pizza + "\n");}
}

运行结果：

--- Making a New York Style Cheese Pizza ---
Preparing New York Style Cheese Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a ---- New York Style Cheese Pizza ----
Thin Crust Dough
Marinara Sauce
Reggiano Cheese--- Making a Chicago Style Cheese Pizza ---
Preparing Chicago Style Cheese Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Joel ordered a ---- Chicago Style Cheese Pizza ----
ThickCrust style extra thick crust dough
Tomato sauce with plum tomatoes
Shredded Mozzarella--- Making a New York Style Clam Pizza ---
Preparing New York Style Clam Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a ---- New York Style Clam Pizza ----
Thin Crust Dough
Marinara Sauce
Reggiano Cheese
Fresh Clams from Long Island Sound--- Making a Chicago Style Clam Pizza ---
Preparing Chicago Style Clam Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Joel ordered a ---- Chicago Style Clam Pizza ----
ThickCrust style extra thick crust dough
Tomato sauce with plum tomatoes
Shredded Mozzarella
Frozen Clams from Chesapeake Bay--- Making a New York Style Pepperoni Pizza ---
Preparing New York Style Pepperoni Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a ---- New York Style Pepperoni Pizza ----
Thin Crust Dough
Marinara Sauce
Reggiano Cheese
Garlic, Onion, Mushrooms, Red Pepper
Sliced Pepperoni--- Making a Chicago Style Pepperoni Pizza ---
Preparing Chicago Style Pepperoni Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Joel ordered a ---- Chicago Style Pepperoni Pizza ----
ThickCrust style extra thick crust dough
Tomato sauce with plum tomatoes
Shredded Mozzarella
Black Olives, Spinach, Eggplant
Sliced Pepperoni--- Making a New York Style Veggie Pizza ---
Preparing New York Style Veggie Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Ethan ordered a ---- New York Style Veggie Pizza ----
Thin Crust Dough
Marinara Sauce
Reggiano Cheese
Garlic, Onion, Mushrooms, Red Pepper--- Making a Chicago Style Veggie Pizza ---
Preparing Chicago Style Veggie Pizza
Bake for 25 minutes at 350
Cutting the pizza into diagonal slices
Place pizza in official PizzaStore box
Joel ordered a ---- Chicago Style Veggie Pizza ----
ThickCrust style extra thick crust dough
Tomato sauce with plum tomatoes
Shredded Mozzarella
Black Olives, Spinach, Eggplant进程已结束,退出代码0

三、比较工厂模式与抽象工厂模式

• 工厂方法使用继承: 把对象的创建委托给子类，子类实现工厂方法来创建对象。
• 抽象工厂使用对象组合(在): 对象的创建被实现在工厂接口所暴露出来的方法中。

本文来自互联网用户投稿，文章观点仅代表作者本人，不代表本站立场，不承担相关法律责任。如若转载，请注明出处。 如若内容造成侵权/违法违规/事实不符，请点击【内容举报】进行投诉反馈！