Question

这是我的代码

public class FactoryPatternDemo {
public static void main(String[]args)
{
    AbstractFactory shapeFactory=new ShapeFactory();

    //tramite la fabbrica di figura geometrica disegno un rettangolo..
    Shape shape1=shapeFactory.getShape("rEcTaNgLe");
    shape1.draw();

    System.out.println();

    //..e un triangolo
    Shape shape2=shapeFactory.getShape("triangle");
    shape2.draw();
}

形状工厂：

public class ShapeFactory extends AbstractFactory{

public ShapeFactory(){

}

@Override
public Shape getShape(String shapeType)
{
    if (shapeType==null)
            return null;
    if (shapeType.equalsIgnoreCase("RECTANGLE"))
            return new Rectangle();
    if (shapeType.equalsIgnoreCase("TRIANGLE"))
            return new Triangle();
    return null;
}

抽象工厂：

public abstract class AbstractFactory {
public abstract Shape getShape(String shapeType);}

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public interface Shape {
void draw();}

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public class Rectangle implements Shape {

@Override
public void draw() {
    for(int i=0; i<5; i++)
    {
        if(i==0 || i==4)
        {
            for(int j=0; j<10; j++)
            {
                System.out.print("*");
            }
        }
        else
        {
            for(int j=0; j<10; j++)
            {
                if(j==0||j==9)
                    System.out.print("*");
                else
                    System.out.print(" ");
            }
        }
        System.out.print("\n");
    }

}

我的问题是：这是实现抽象工厂模式的正确方法吗？客户端应该只能在FactoryPatternDemo类中看到抽象的东西或接口，但是这行代码：

 AbstractFactory shapeFactory=new ShapeFactory();

显示具体工厂的名称。这是一个错误吗？谢谢你们

Answer 1

嗯，我肯定不会使用这个设计！它起泡的原因至少有以下几个原因：

ShapeFactory.getShape()使用一种不是面向对象设计的开关。
ShapeFactory是编译时依赖于所有Shape对象的。
没有人不能扩展你的图书馆！试着想象一下，不的某个人如何控制你的ShapeFactory想要添加一个新形状......不可能！
我看不出AbstractFactory应该是抽象类而不是接口的任何原因。在我看来，它似乎是C ++的遗产，而不是Java设计。

了解java.sql.DriverManager.getConnection(connectionString)方法的实现方式。最好的方法是观看源代码。

非常粗略的想法总结（它隐藏在很多私有方法中）。它或多或少是责任链的实现，尽管没有相关的驱动因素列表。

DriverManager管理一系列驱动程序。每个驱动程序必须通过调用其方法DriverManager将自己注册到registerDriver()。在请求连接时，getConnection(connectionString)方法依次调用传递connectionString的驱动程序。如果给定的连接字符串在其权限范围内，则每个驱动程序都知道。如果是，则创建连接并返回它。否则，控件将传递给下一个驱动程序。类比：

drivers：your concrete ShapeFactories
连接字符串：形状的类型
连接：形状的实例

我会尝试这样的事情：

public class ShapeManager {
    public void registerFactory(ShapeFactory factory) {
        // store the factory to the internal list
    }
    public shape getShape(String shapeType) {
        // go through the list of registered factories until one of them returns non-null
    }
}

public interface ShapeFactory {
    /**
     * Returns an instance of a shape, if shapeType is supported
     */
    public shape getShape(String shapeType);
}

public class TriangleFactory implements ShapeFactory {
    public static final String SHAPE_TYPE = "Triangle";
    @Override 
    public shape getShape(String shapeType) {
        if (SHAPE_TYPE.equals(shapeType) {
            return new Triangle();
        }
    }
}

public class RectangleFactory implements ShapeFactory {
    public static final String SHAPE_TYPE = "Rectangle";
    @Override 
    public shape getShape(String shapeType) {
        if (SHAPE_TYPE.equals(shapeType) {
            return new Triangle();
        }
    }
}

public class Client {
    ShapeFactory factory;

    // This is performed somehow on a global level, maybe by Spring configuration or so
    // However it is *not* part of the ShapeFactory so anyone may add their own shapes,
    // apart from those provided by default by your shape library.
    public void setUp() {
       factory = new ShapeFactory();
       factory.registerFactory(new TriangleFactory());
       factory.registerFactory(new RectangleFactory());
    }

    public void use() {
        final Shape triangle = factory.getShape("Triangle");
        final Shape rectangle = factory.getShape("Rectangle");
    }
}

抽象工厂模式 - 实现它的正确方法

1 个答案: