设计模式--工厂模式

披萨项目：要方便披萨品种的扩展、要便于维护、要能运行时扩展

披萨族设计：

 1、正常逻辑

抽象披萨类(Pizza )、两个具体披萨类（CheesePizza、GreekPizza）、披萨订单类（OrderPizza ）

如果我们有新的披萨类，就要对OrderPizza类，增加else if，违背了开闭原则。

public abstract class Pizza {
    protected String name;
    
    public abstract void prepare();

    
    public void bake() {
        System.out.println(name + " baking;");
    }

    
    public void cut() {
        System.out.println(name + " cutting;");
    }

    
    public void box() {
        System.out.println(name + " boxing;");
    }

    public void setname(String name) {
        this.name = name;
    }
}

public class CheesePizza extends Pizza {
   @Override
   public void prepare() {
      super.setname("CheesePizza");
      System.out.println(name + " preparing;");
   }
}

public class GreekPizza extends Pizza {
   @Override
   public void prepare() {
      super.setname("GreekPizza");
      System.out.println(name + " preparing;");
   }
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class OrderPizza {
   public OrderPizza() {
      Pizza pizza = null;
      String ordertype;
      do {
         ordertype = gettype();
         if (ordertype.equals("cheese")) {
            pizza = new CheesePizza();
         } else if (ordertype.equals("greek")) {
            pizza = new GreekPizza();
         } else  {
            break;
         }
         pizza.prepare();
         pizza.bake();
         pizza.cut();
         pizza.box();
      } while (true);
   }

   private String gettype() {
      try {
         BufferedReader strin = new BufferedReader(new InputStreamReader(System.in));
         System.out.println("input pizza type: ");
         String str = strin.readLine();
         return str;
      } catch (IOException e) {
         e.printStackTrace();
         return "";
      }
   }

   public static void main(String [] args) {
      OrderPizza orderPizza = new OrderPizza();

   }
}

2、使用简单工厂模式

简单工厂模式的设计方案：定义一个实例化披萨对象的类，封装创建对象的代码

简单工厂模式：定义了一个创建对象的类，由这个类来封装实例化对象的行为

增加一个简单工厂类（SimplePizzaFactory ）和修改披萨订单类（OrderPizzaBySimple ）

public class SimplePizzaFactory {
   public Pizza createPizza(String ordertype) {
      Pizza pizza = null;
      if (ordertype.equals("cheese")) {
         pizza = new CheesePizza();
      } else if (ordertype.equals("greek")) {
         pizza = new GreekPizza();
      }
      return pizza;
   }
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class OrderPizzaBySimple {
    private SimplePizzaFactory simplePizzaFactory;

    public OrderPizzaBySimple(SimplePizzaFactory simplePizzaFactory) {
        this.simplePizzaFactory = simplePizzaFactory;
        Pizza pizza = null;
        String ordertype;
        do {
            ordertype = gettype();
            pizza = this.simplePizzaFactory.createPizza(ordertype);
            if (pizza != null) {
                pizza.prepare();
                pizza.bake();
                pizza.cut();
                pizza.box();
            }

        } while (true);

    }

    private String gettype() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(
                    System.in));
            System.out.println("input pizza type:");
            String str = strin.readLine();

            return str;
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }
    }

    public static void main(String [] args) {
        SimplePizzaFactory simplePizzaFactory = new SimplePizzaFactory();
        OrderPizzaBySimple orderPizza = new OrderPizzaBySimple(simplePizzaFactory);

    }
}

3、使用工厂模式

披萨项目新需求的困惑：披萨项目加盟店

如果用简单工厂模式来处理，每个加盟店都要创建一个简单工厂。

工厂方法模式设计方案：将披萨项目里的披萨对象实例化功能抽象成抽象方法，在 不同加盟店具体实现功能。

工厂方法模式：定义了一个创建对象的抽象方法，由子类决定要实例化的类。 工厂方法模式将对象的实例化推迟到子类

披萨抽象类（OrderPizzaByFactory）、两个具体的子类（伦敦加盟商LDOrderPizza、纽约加盟商NYOrderPizza）

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public abstract class OrderPizzaByFactory {
    abstract Pizza createPizza(String ordertype);

    public OrderPizzaByFactory() {
        Pizza pizza = null;
        String ordertype;

        do {
            ordertype = gettype();
            pizza = createPizza(ordertype);
            pizza.prepare();
            pizza.bake();
            pizza.cut();
            pizza.box();
        } while (true);
    }


    private String gettype() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(
                    System.in));
            System.out.println("input pizza type:");
            String str = strin.readLine();

            return str;
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }
    }
}

public class LDOrderPizza extends OrderPizzaByFactory {
   @Override
   Pizza createPizza(String ordertype) {
      Pizza pizza = null;

      if (ordertype.equals("cheese")) {
         pizza = new LDCheesePizza();
      } else if (ordertype.equals("greek")) {
         pizza = new LDGreekPizza();
      }
      return pizza;

   }

   public static class LDCheesePizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("CheesePizza");
         System.out.println(name + " preparing;");
      }
   }


   public static class LDGreekPizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("LDGreekPizza");
         System.out.println(name + " preparing;");
      }
   }

   public static void main(String [] args) {
      OrderPizzaByFactory orderPizza = new LDOrderPizza();
   }

}

public class NYOrderPizza extends OrderPizzaByFactory {
   @Override
   Pizza createPizza(String ordertype) {
      Pizza pizza = null;

      if (ordertype.equals("cheese")) {
         pizza = new NYCheesePizza();
      } else if (ordertype.equals("greek")) {
         pizza = new NYGreekPizza();
      }
      return pizza;

   }

   public static class NYCheesePizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("NYCheesePizza");
         System.out.println(name + " preparing;");
      }
   }


   public static class NYGreekPizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("NYCheesePizza");
         System.out.println(name + " preparing;");
      }
   }

   public static void main(String [] args) {
      OrderPizzaByFactory orderPizza = new NYOrderPizza();
   }

}

4、升级抽象工程模式

增加抽象工厂类（AbsFactory）、两个具体的子类工厂（伦敦工厂NYFactory、纽约工厂LDFactory）、披萨订单类（OrderPizzaByAbs）

public interface AbsFactory {
   public Pizza CreatePizza(String ordertype) ;
}

public class NYFactory implements AbsFactory {
   @Override
   public Pizza CreatePizza(String ordertype) {
      Pizza pizza = null;

      if (ordertype.equals("cheese")) {
         pizza = new NYCheesePizza();
      } else if (ordertype.equals("greek")) {
         pizza = new NYGreekPizza();
      }
      return pizza;

   }

   public static class NYCheesePizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("NYCheesePizza");
         System.out.println(name + " preparing;");
      }
   }

   public static class NYGreekPizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("NYCheesePizza");
         System.out.println(name + " preparing;");
      }
   }
}

public class LDFactory implements AbsFactory {
   @Override
   public Pizza CreatePizza(String ordertype) {
      Pizza pizza = null;
      if (ordertype.equals("cheese")) {
         pizza = new LDCheesePizza();
      } else if (ordertype.equals("greek")) {
         pizza = new LDGreekPizza();
      }
      return pizza;
   }

   public static class LDCheesePizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("CheesePizza");
         System.out.println(name + " preparing;");
      }
   }

   public static class LDGreekPizza extends Pizza{
      @Override
      public void prepare() {
         super.setname("LDGreekPizza");
         System.out.println(name + " preparing;");
      }
   }
}

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class OrderPizzaByAbs {
    private AbsFactory mFactory;

    public OrderPizzaByAbs(AbsFactory mFactory) {
        setFactory(mFactory);
    }

    public void setFactory(AbsFactory mFactory) {
        Pizza pizza = null;
        String ordertype;
        this.mFactory = mFactory;
        do {
            ordertype = gettype();
            pizza = mFactory.CreatePizza(ordertype);
            if (pizza != null) {
                pizza.prepare();
                pizza.bake();
                pizza.cut();
                pizza.box();
            }

        } while (true);

    }

    private String gettype() {
        try {
            BufferedReader strin = new BufferedReader(new InputStreamReader(
                    System.in));
            System.out.println("input pizza type:");
            String str = strin.readLine();

            return str;
        } catch (IOException e) {
            e.printStackTrace();
            return "";
        }
    }

    public static void main(String [] args) {
        AbsFactory absFactory = new LDFactory();
        OrderPizzaByAbs orderPizzaByAbs = new OrderPizzaByAbs(absFactory);
    }
}