Factory Method Pattern(工廠模式)

• Definition

The Factory Method Pattern defines an interface for creating an object, but lets subclasses decide which class to instantiate. Factory Method lets a class defer instantiation to subclasses.

• Class Diagram

• Product Role

public abstract class Product {
    public void method1() {
    //doSomething
    }

public abstract void method2() ;

}

• ConcreteProduct Role

public ConcreteProduct1 extend Product {
    public void method2() {
        //doSomething
    }
}

public ConcreteProduct2 extend Product {
    public void method2() {
        //doSomething
    }
}

• Creator Role

public abstract class Creator {
    public abstract <T extends Product> T createProduct(Class<T> c);
}

• ConcreteCreator Role

public class ConcreteCreator extends Creator {
    public <T extends Product> T createProduct(Class<T> c) {
        Product product=null;
        try {
            product = (Product)Class.forName(c.getName()).newInstance();
        } catch (Exception e) {
            //error process
        }
        Return (T)product;
    }
}

• Client Role

public class Client {
    public static void main(String[] args) {
        Creator creator = new ConcreteCreator();
        Product product = creator.creatorProduct(ConcreteProduct1.class);
        //doSomething
    }
}