Bridge 模式如何与 Spring Boot 配合使用？

Question

我正在学习使用 Spring boot 的桥接模式，并且我正在使用 Chatgpt 来帮助我完成该过程，但我无法理解它如何知道何时需要在 EmailNotification 中使用 EmailSender 和在它给我的示例中的 SmsNotification 中使用 SmsSender 。我对以下事实感到困惑：EmailSender 和 SmsSender 都配置为返回 Sender 类型，加上 EmailNotification 和 SmsNotification 在其构造函数中也具有 Sender 类型。

那么，他们如何知道他们必须使用哪个发件人？这是我试图理解的代码。

// Sender.java
public interface Sender {
    void send(String message);
}

// EmailSender.java
public class EmailSender implements Sender {
    @Override
    public void send(String message) {
        System.out.println("Sending email: " + message);
    }
}

// SmsSender.java
public class SmsSender implements Sender {
    @Override
    public void send(String message) {
        System.out.println("Sending SMS: " + message);
    }
}

// Notification.java
public abstract class Notification {
    protected Sender sender;

    protected Notification(Sender sender) {
        this.sender = sender;
    }

    public void notifyUser(String message) {
        sender.send(formatMessage(message));
    }

    protected abstract String formatMessage(String message); // Método abstracto para formatear el mensaje
}


// EmailNotification.java
public class EmailNotification extends Notification {
    public EmailNotification(Sender sender) {
        super(sender);
    }

    @Override
    protected String formatMessage(String message) {
        return "Email Notification: " + message;
    }
}

// SmsNotification.java
public class SmsNotification extends Notification {
    public SmsNotification(Sender sender) {
        super(sender);
    }

    @Override
    protected String formatMessage(String message) {
        return "SMS Notification: " + message;
    }
}


@Configuration
public class AppConfig {

    @Bean
    public Sender emailSender() {
        return new EmailSender();
    }

    @Bean
    public Sender smsSender() {
        return new SmsSender();
    }

    @Bean
    public Notification emailNotification(Sender emailSender) {
        return new EmailNotification(emailSender);
    }

    @Bean
    public Notification smsNotification(Sender smsSender) {
        return new SmsNotification(smsSender);
    }
}

@RestController
@RequestMapping("/notifications")
public class NotificationController {

    private final Notification emailNotification;
    private final Notification smsNotification;

    @Autowired
    public NotificationController(Notification emailNotification, Notification smsNotification) {
        this.emailNotification = emailNotification;
        this.smsNotification = smsNotification;
    }

    @GetMapping("/email")
    public ResponseEntity<String> sendEmailNotification() {
        emailNotification.notifyUser("Hello via Email!");
        return ResponseEntity.ok("Email notification sent!");
    }

    @GetMapping("/sms")
    public ResponseEntity<String> sendSmsNotification() {
        smsNotification.notifyUser("Hello via SMS!");
        return ResponseEntity.ok("SMS notification sent!");
    }
}

我对它如何知道 EmailNotification 在 AppConfig 中使用 EmailSender 以及 SmsNotification 的使用方式感到困惑，因为即使返回类型不同，方法签名也是相同的。无法理解它如何将每个通知与每个发件人相关联。是因为“emailNotification”和“smsNotification”bean 定义中的参数名称“emailSender”和“smsSender”吗？

我认为我不了解 Spring 的依赖注入，因为类似的事情发生在 Controller 构造函数中。由于 emailNotification 和 SmsNotification 都是通知类型，它如何知道使用哪种实现？我感觉这是因为参数名称与 AppConfig 中定义的参数名称相同。我说得对吗？

谢谢！

Answer 1

好吧，发生这种情况是因为正如我所假设和@lane.maxwell 所证实的那样，bean 名称是“方法名称”。所以我使用@Qualifier来消除这种歧义：

@Configuration
public class NotificationConfig {

    @Bean
    @Qualifier("emailSender")
    public Sender emailSender() {
        return new EmailSender();
    }

    @Bean
    @Qualifier("smsSender")
    public Sender smsSender() {
        return new SmsSender();
    }

    @Bean
    @Qualifier("emailNotification")
    public Notification emailNotification(@Qualifier("emailSender") Sender emailSender) {
        return new EmailNotification(emailSender);
    }

    @Bean
    @Qualifier("smsNotification")
    public Notification smsNotification(@Qualifier("smsSender") Sender smsSender) {
        return new SmsNotification(smsSender);
    }
}

@RestController
@RequestMapping("/notifications")
public class NotificationController {

    private final Notification emailNotification;
    private final Notification smsNotification;

    @Autowired
    public NotificationController(
        @Qualifier("emailNotification") Notification emailNotification,
        @Qualifier("smsNotification") Notification smsNotification) {
        this.emailNotification = emailNotification;
        this.smsNotification = smsNotification;
    }

    @GetMapping("/email")
    public ResponseEntity<String> sendEmailNotification() {
        emailNotification.notifyUser("Hello via Email!");
        return ResponseEntity.ok("Email notification sent!");
    }

    @GetMapping("/sms")
    public ResponseEntity<String> sendSmsNotification() {
        smsNotification.notifyUser("Hello via SMS!");
        return ResponseEntity.ok("SMS notification sent!");
    }
}