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一、工廠模式

1. 什么是工廠模式？

• 工廠模式（Factory Pattern）提供了一種創建對象的最佳方式，是 Java 中最常用的設計模式之一。這種類型的設計模式屬于創建型模式。
• 在工廠模式中，我們在創建對象時不會對客戶端暴露創建邏輯，并且是通過使用一個共同的接口來指向新創建的對象。

**意圖：**定義一個創建對象的接口，讓其子類自己決定實例化哪一個工廠類，工廠模式使其創建過程延遲到子類進行。(依賴倒置原則)

**主要解決：**主要解決接口選擇的問題。

**何時使用：**我們明確地計劃不同條件下創建不同實例時。

**如何解決：**讓其子類實現工廠接口，返回的也是一個抽象的產品。

**關鍵代碼：**創建過程在其子類執行。

應用實例：

• 您需要一輛汽車，可以直接從工廠里面提貨，而不用去管這輛汽車是怎么做出來的，以及這個汽車里面的具體實現。
• Mybatis換數據庫只需換方言和驅動就可以。

優點：

• 一個調用者想創建一個對象，只要知道其名稱就可以了。
• 擴展性高，如果想增加一個產品，只要擴展一個工廠類就可以。
• 屏蔽產品的具體實現，調用者只關心產品的接口。

**缺點：**每次增加一個產品時，都需要增加一個具體類和對象實現工廠，使得系統中類的個數成倍增加，在一定程度上增加了系統的復雜度，同時也增加了系統具體類的依賴。這并不是什么好事。

使用場景：

• 日志記錄器：記錄可能記錄到本地硬盤、系統事件、遠程服務器等，用戶可以選擇記錄日志到什么地方。
• 數據庫訪問，當用戶不知道最后系統采用哪一類數據庫，以及數據庫可能有變化時。
• 設計一個連接服務器的框架，需要三個協議，“POP3”、“IMAP”、“HTTP”，可以把這三個作為產品類，共同實現一個接口。

**注意事項：**作為一種創建類模式，在任何需要生成復雜對象的地方，都可以使用工廠方法模式。有一點需要注意的地方就是復雜對象適合使用工廠模式，而簡單對象，特別是只需要通過 new 就可以完成創建的對象，無需使用工廠模式。如果使用工廠模式，就需要引入一個工廠類，會增加系統的復雜度。

2. 加盟披薩店案例

案例描述：你有一家披薩店，經營有成，擊敗了許多的競爭者，現在你想開擴大市場，建立加盟店。因為區域的差異，每家加盟店都可能想要提供不同風味的比薩(比方說紐約、芝加哥、加州)，這受到了開店地點及該地區比薩美食家口味的影響。那么如何設計呢？

下面是案例的UML模型設計圖：

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");} }

披薩店測試：

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");} }

運行結果：

--- 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進程已結束,退出代碼0

二、抽象工程模式

1. 什么是抽象工廠模式？

• 抽象工廠模式（Abstract Factory Pattern）是圍繞一個超級工廠創建其他工廠。該超級工廠為其他工廠的父工廠。這種類型的設計模式屬于創建型模式，它提供了一種創建對象的最佳方式。
• 在抽象工廠模式中，接口是負責創建一個相關對象的工廠，不需要顯式指定它們的類。每個生成的工廠都能按照工廠模式提供對象。

**意圖：**提供一個創建一系列相關或相互依賴對象的接口，而無需指定它們具體的類。

**主要解決：**主要解決接口選擇的問題。

**何時使用：**系統的產品有多于一個的產品族，而系統只消費其中某一族的產品。

**如何解決：**在一個產品族里面，定義多個產品。

**關鍵代碼：**在一個工廠里聚合多個同類產品。

**應用實例：**工作了，為了參加一些聚會，肯定有兩套或多套衣服吧，比如說有商務裝（成套，一系列具體產品）、時尚裝（成套，一系列具體產品），甚至對于一個家庭來說，可能有商務女裝、商務男裝、時尚女裝、時尚男裝，這些也都是成套的，即一系列具體產品。假設一種情況，在您的家中，某一個衣柜（具體工廠）只能存放某一種這樣的衣服（成套，一系列具體產品），每次拿這種成套的衣服時也自然要從這個衣柜中取出了。用 OOP 的思想去理解，所有的衣柜（具體工廠）都是衣柜類的（抽象工廠）某一個，而每一件成套的衣服又包括具體的上衣（某一具體產品），褲子（某一具體產品），這些具體的上衣其實也都是上衣（抽象產品），具體的褲子也都是褲子（另一個抽象產品）。

**優點：**當一個產品族中的多個對象被設計成一起工作時，它能保證客戶端始終只使用同一個產品族中的對象。

**缺點：**產品族擴展非常困難，要增加一個系列的某一產品，既要在抽象的 Creator 里加代碼，又要在具體的里面加代碼。

使用場景： 1、QQ 換皮膚，一整套一起換。 2、生成不同操作系統的程序。

**注意事項：**產品族難擴展，產品等級易擴展。

2. 給加盟披薩店新增原料工廠

案例描述：你有一家披薩店，經營有成，擊敗了許多的競爭者，現在你想開擴大市場，建立加盟店。因為區域的差異，每家加盟店都可能想要提供不同風味的比薩(比方說紐約、芝加哥、加州)，這受到了開店地點及該地區比薩美食家口味的影響。那么如何設計呢？這是我們工廠模式的案例，現在我們在此案例上加點東西，我們希望所有的加盟店都使用統一的調料(原料)：面團、醬料、臘腸、芝士、蔬菜、肉等。我們可以建造原料工廠來滿足這種需求。

下面是UML設計模型：

下面給出核心實現代碼;

**
**

披薩抽象類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();} }

具體的某種披薩類CheesePizza:

public class CheesePizza extends Pizza {//原料工廠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();} }

披薩店抽象類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;} }

紐約披薩店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;} }

原料工廠抽象類****PizzaIngredientFactory：

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

具體的紐約原料工廠****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();} }

某類型的具體原料產品****Mushroom：

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

測試運行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");} }

運行結果：

--- 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進程已結束,退出代碼0

三、比較工廠模式與抽象工廠模式

• 工廠方法使用繼承: 把對象的創建委托給子類，子類實現工廠方法來創建對象。
• 抽象工廠使用對象組合(在): 對象的創建被實現在工廠接口所暴露出來的方法中。

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