java装饰器设计模式

装饰器设计模式来达到类似效果。这种模式通常用于动态地添加功能，特别适合在类或接口上扩展行为。Java装饰器模式通常涉及创建一个装饰器类，该类实现被装饰对象的接口并持有被装饰对象的实例。

装饰器模式示例：

假设我们有一个MessageService接口，以及其实现SimpleMessageService。

// 接口
public interface MessageService {String sendMessage(String message);
}// 实现
public class SimpleMessageService implements MessageService {@Overridepublic String sendMessage(String message) {return "Sending message: " + message;}
}

我们希望动态添加功能，比如记录消息发送的日志，或对消息内容进行加密。

装饰器类：

// 装饰器类
public class MessageServiceDecorator implements MessageService {private MessageService decoratedService;public MessageServiceDecorator(MessageService service) {this.decoratedService = service;}@Overridepublic String sendMessage(String message) {return decoratedService.sendMessage(message);}
}// 日志装饰器
public class LoggingMessageService extends MessageServiceDecorator {public LoggingMessageService(MessageService service) {super(service);}@Overridepublic String sendMessage(String message) {System.out.println("Logging: " + message);return super.sendMessage(message);}
}// 加密装饰器
public class EncryptedMessageService extends MessageServiceDecorator {public EncryptedMessageService(MessageService service) {super(service);}@Overridepublic String sendMessage(String message) {String encryptedMessage = encrypt(message);return super.sendMessage(encryptedMessage);}private String encrypt(String message) {// 简单的加密示例return new StringBuilder(message).reverse().toString();}
}

使用装饰器：

public class Main {public static void main(String[] args) {MessageService service = new SimpleMessageService();// 添加日志功能service = new LoggingMessageService(service);// 添加加密功能service = new EncryptedMessageService(service);// 调用sendMessageSystem.out.println(service.sendMessage("Hello, World!"));}
}