工厂模式

1类图

2定义：

一个用于创建对象的接口，让子类决定实例化那个类

3使用场景

• 需要生成复杂的对象。
• 用new就可以创建的对象无需使用工厂模式。

4具体实现

• 1抽象产品类

public abstract class Product {    public abstract void method();}

• 2具体产品A类

public class ConcreteProductA extends Product {    @Override    public void method() {        // TODO Auto-generated method stub        System.out.println("A");    }}

• 3具体产品B类

public class ConcreteProductB extends Product {    @Override    public void method() {        // TODO Auto-generated method stub        System.out.println("B");    }}

• 4抽象工厂类

public abstract class Factory {    public abstract Product createProduct();    //public abstract<T extends Product> T createProduct(Class<T> clz);}

• 5具体工厂类

public class ConcreteFactory extends Factory{    @Override    public Product createProduct() {        // TODO Auto-generated method stub        //创建ConcreteProductA();        return new ConcreteProductA();        //return new ConcreteProductB();    }}

• 客户类

public class Client {    public static void main(String[] args) {        Factory factory = new ConcreteFactory();        Product product = factory.createProduct();        //Product product = factory.createProduct(ConcreteProductB.class);        product.method();    }}

5利用反射的方式决定创建那个产品类的实例

• 更改抽象工厂类

public abstract class Factory {    //public abstract Product createProduct();    public abstract<T extends Product> T createProduct(Class<T> clz);}

• 更改具体工厂类

public class ConcreteFactory extends Factory{    @Override    public <T extends Product> T createProduct(Class<T> clz) {        // TODO Auto-generated method stub        Product p = null;        try {            p = (Product) Class.forName(clz.getName()).newInstance();        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return (T)p;    }/*    @Override    public Product createProduct() {        // TODO Auto-generated method stub        //创建ConcreteProductA();        return new ConcreteProductA();        //return new ConcreteProductB();    }*/}

• 客户类

public class Client {    public static void main(String[] args) {        Factory factory = new ConcreteFactory();        //Product product = factory.createProduct();        Product product = factory.createProduct(ConcreteProductB.class);        product.method();    }}

6每个产品都具体化抽象工厂类

• 创建产品A的具体工厂类

public class ConcreteFactoryA extends Factory {    @Override    public Product createProduct() {        // TODO Auto-generated method stub        return new ConcreteProductA();    }}

• 创建产品B的具体工厂类

public class ConcreteFactoryB extends Factory {    @Override    public Product createProduct() {        // TODO Auto-generated method stub        return new ConcreteProductB();    }}

• 客户类

public class Client {    public static void main(String[] args) {        //Factory factory = new ConcreteFactory();        //Product product = factory.createProduct();        //Product product = factory.createProduct(ConcreteProductB.class);        //product.method();        Factory factory = new ConcreteFactoryA();        Product productA = factory.createProduct();        productA.method();    }}