在上一课，我们研究了工厂方法模式。我们用它来扩展我们的咖啡业务并开设了几个新地点。今天，我们将继续实现业务现代化。使用抽象工厂模式，我们将为在线订购咖啡的新桌面应用程序奠定基础。在编写桌面应用程序时，我们应该始终考虑跨平台支持。我们的应用程序必须同时在 macOS 和 Windows 上运行（剧透：对 Linux 的支持留给您作为家庭作业来实现）。我们的应用程序会是什么样子？非常简单：它将是一个由文本字段、选择字段和按钮组成的表单。如果您有使用不同操作系统的经验，您肯定会注意到 Windows 上的按钮呈现方式与 Mac 上的不同。和其他一切一样……好吧，让我们开始吧。
public interface Button {}
public interface Select {}
public interface TextField {}
对于每个操作系统，我们必须创建操作系统风格的界面元素。我们将为 Windows 和 MacOS 编写代码。让我们为 Windows 创建实现：
public class WindowsButton implements Button {
}
public class WindowsSelect implements Select {
}
public class WindowsTextField implements TextField {
}
现在我们对 MacOS 做同样的事情：
public class MacButton implements Button {
}
public class MacSelect implements Select {
}
public class MacTextField implements TextField {
}
高超。如您所见，我们还没有做任何复杂的事情。接下来的一切也很简单。通过类比产品，我们为每个操作系统创建各种工厂实现。让我们从 Windows 开始：
public class WindowsGUIFactory implements GUIFactory {
public WindowsGUIFactory() {
System.out.println("Creating GUIFactory for Windows OS");
}
public Button createButton() {
System.out.println("Creating Button for Windows OS");
return new WindowsButton();
}
public TextField createTextField() {
System.out.println("Creating TextField for Windows OS");
return new WindowsTextField();
}
public Select createSelect() {
System.out.println("Creating Select for Windows OS");
return new WindowsSelect();
}
}
我们在方法和构造函数中添加了一些控制台输出，以进一步说明正在发生的事情。现在对于 macOS：
public class MacGUIFactory implements GUIFactory {
public MacGUIFactory() {
System.out.println("Creating GUIFactory for macOS");
}
@Override
public Button createButton() {
System.out.println("Creating Button for macOS");
return new MacButton();
}
@Override
public TextField createTextField() {
System.out.println("Creating TextField for macOS");
return new MacTextField();
}
@Override
public Select createSelect() {
System.out.println("Creating Select for macOS");
return new MacSelect();
}
}
public class CoffeeOrderForm {
private final TextField customerNameTextField;
private final Select coffeeTypeSelect;
private final Button orderButton;
public CoffeeOrderForm(GUIFactory factory) {
System.out.println("Creating coffee order form");
customerNameTextField = factory.createTextField();
coffeeTypeSelect = factory.createSelect();
orderButton = factory.createButton();
}
}
public class Application {
private CoffeeOrderForm coffeeOrderForm;
public void drawCoffeeOrderForm() {
// Determine the name of the operating system through System.getProperty()
String osName = System.getProperty("os.name").toLowerCase();
GUIFactory guiFactory;
if (osName.startsWith("win")) { // For Windows
guiFactory = new WindowsGUIFactory();
} else if (osName.startsWith("mac")) { // For Mac
guiFactory = new MacGUIFactory();
} else {
System.out.println("Unknown OS. Unable to draw form :(");
return;
}
coffeeOrderForm = new CoffeeOrderForm(guiFactory);
}
public static void main(String[] args) {
Application application = new Application();
application.drawCoffeeOrderForm();
}
}
如果我们在 Windows 上运行该应用程序，我们会得到以下输出：
Creating GUIFactory for Windows OS
Creating coffee order form
Creating TextField for Windows OS
Creating Select for Windows OS
Creating Button for Windows OS
在 Mac 上，输出将如下所示：
Creating GUIFactory for macOS
Creating coffee order form
Creating TextField for macOS
Creating Select for macOS
Creating Button for macOS
// Define common product interfaces
public interface ProductA {}
public interface ProductB {}
// Create various implementations (families) of our products
public class SpecificProductA1 implements ProductA {}
public class SpecificProductB1 implements ProductB {}
public class SpecificProductA2 implements ProductA {}
public class SpecificProductB2 implements ProductB {}
// Create an abstract factory
public interface AbstractFactory {
ProductA createProductA();
ProductB createProductB();
}
// Implement the abstract factory in order to create products in family 1
public class SpecificFactory1 implements AbstractFactory {
@Override
public ProductA createProductA() {
return new SpecificProductA1();
}
@Override
public ProductB createProductB() {
return new SpecificProductB1();
}
}
// Implement the abstract factory in order to create products in family 2
public class SpecificFactory2 implements AbstractFactory {
@Override
public ProductA createProductA() {
return new SpecificProductA2();
}
@Override
public ProductB createProductB() {
return new SpecificProductB2();
}
}
以下是我们将在课程中介绍的内容：
现在我们将根据这些指令编写代码：
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