在上一課，我們研究了工廠方法模式。我們用它來擴展我們的咖啡業務並開設了幾個新地點。今天，我們將繼續實現業務現代化。使用抽象工廠模式，我們將為在線訂購咖啡的新桌面應用程序奠定基礎。在編寫桌面應用程序時，我們應該始終考慮跨平台支持。我們的應用程序必須同時在 macOS 和 Windows 上運行（劇透：對 Linux 的支持留給您作為家庭作業來實現）。我們的應用程序會是什麼樣子？非常簡單：它將是一個由文本字段、選擇字段和按鈕組成的表單。如果您有使用不同操作系統的經驗，您肯定會注意到 Windows 上的按鈕呈現方式與 Mac 上的不同。和其他一切一樣……好吧，讓我們開始吧。
public interface Button {}
public interface Select {}
public interface TextField {}
對於每個操作系統，我們必須創建操作系統風格的界面元素。我們將為 Windows 和 MacOS 編寫代碼。讓我們為 Windows 創建實現：
public class WindowsButton implements Button {
}
public class WindowsSelect implements Select {
}
public class WindowsTextField implements TextField {
}
現在我們對 MacOS 做同樣的事情：
public class MacButton implements Button {
}
public class MacSelect implements Select {
}
public class MacTextField implements TextField {
}
高超。如您所見，我們還沒有做任何復雜的事情。接下來的一切也很簡單。通過類比產品，我們為每個操作系統創建各種工廠實現。讓我們從 Windows 開始：
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();
}
}
我們在方法和構造函數中添加了一些控制台輸出，以進一步說明正在發生的事情。現在對於 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();
}
}
如果我們在 Windows 上運行該應用程序，我們會得到以下輸出：
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，輸出將如下所示：
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();
}
}
以下是我們將在課程中介紹的內容：
現在我們將根據這些指令編寫代碼：
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