观察者模式在Java微服务间的使用

一.、使用RabbitMQ来实现

(1) 生产者（订单微服务）

import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.stereotype.Service;@Service
public class OrderService {private final RabbitTemplate rabbitTemplate;public OrderService(RabbitTemplate rabbitTemplate) {this.rabbitTemplate = rabbitTemplate;}public void createOrder(Long orderId) {// 创建订单逻辑System.out.println("订单创建成功: " + orderId);// 发送消息到 RabbitMQrabbitTemplate.convertAndSend("order.exchange", "order.created", orderId);}
}

(2) 消费者（通知微服务）

import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;@Component
public class NotificationService {@RabbitListener(queues = "order.queue")public void handleOrderCreated(Long orderId) {System.out.println("【通知服务】订单 " + orderId + " 创建成功，发送通知！");}
}

(3) 配置 RabbitMQ 交换机和队列

import org.springframework.amqp.core.*;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;@Configuration
public class RabbitMQConfig {@Beanpublic DirectExchange orderExchange() {return new DirectExchange("order.exchange");}@Beanpublic Queue orderQueue() {return new Queue("order.queue");}@Beanpublic Binding binding(Queue orderQueue, DirectExchange orderExchange) {return BindingBuilder.bind(orderQueue).to(orderExchange).with("order.created");}
}

二. 使用 Spring Cloud Stream

Spring Cloud Stream 结合 Kafka 或 RabbitMQ，可以简化微服务间的事件驱动架构。

(1) 生产者

import org.springframework.cloud.stream.function.StreamBridge;
import org.springframework.stereotype.Service;@Service
public class OrderService {private final StreamBridge streamBridge;public OrderService(StreamBridge streamBridge) {this.streamBridge = streamBridge;}public void createOrder(Long orderId) {System.out.println("订单创建成功: " + orderId);// 发送事件streamBridge.send("orderCreated-out-0", orderId);}
}

(2) 消费者

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Service;
import java.util.function.Consumer;@Service
public class NotificationService {@Beanpublic Consumer<Long> orderCreated() {return orderId -> System.out.println("【通知服务】订单 " + orderId + " 创建成功，发送通知！");}
}

(3) 配置 application.yml

spring:cloud:stream:bindings:orderCreated-out-0:destination: order-eventsorderCreated-in-0:destination: order-eventsdefaultBinder: rabbit