工厂与抽象工厂 -尊龙游戏旗舰厅官网
本篇文章代码：https://gitee.com/bithachi_admin_admin/mycode/tree/master/设计模式/factory
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01. 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;
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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:
**
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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- 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。
总结
