在Spring Boot中，可以使用MQTT协议来收发消息。以下是一个简单的示例：
1. 添加依赖
在`pom.xml`文件中添加以下依赖：
```xml
<dependency>
<groupId>org.springframework.integration</groupId>
<artifactId>spring-integration-mqtt</artifactId>
<version>5.5.3</version>
</dependency>
```
2. 配置MQTT连接工厂
在`application.properties`文件中添加以下配置：
```properties
spring.mqtt.url=tcp://localhost:1883
spring.mqtt.username=your_username
spring.mqtt.password=your_password
```
3. 创建MQTT消息接收服务
创建一个名为`MqttMessageService`的类，用于接收MQTT消息：
```java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.mqtt.support.MqttHeaders;
import org.springframework.messaging.handler.annotation.Header;
import org.springframework.stereotype.Service;
@Service
public class MqttMessageService {
@MessagingGateway(defaultRequestChannel = "mqttInboundChannel")
public interface MqttGateway {
void subscribe(String topic);
void unsubscribe(String topic);
void publish(String topic, String payload);
}
@Autowired
private MqttGateway mqttGateway;
public void receiveMessage(@Header(MqttHeaders.RECEIVED_TOPIC) String topic, String payload) {
System.out.println("Received message from topic [" + topic + "]: " + payload);
}
}
```
4. 创建MQTT消息发送服务
创建一个名为`MqttOutboundMessageService`的类，用于发送MQTT消息：
```java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.integration.mqtt.MqttPahoClientFactory;
import org.springframework.integration.mqtt.outbound.MqttPahoMessageHandler;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.stereotype.Service;
@Service
public class MqttOutboundMessageService {
@Autowired
private MqttPahoClientFactory mqttClientFactory;
@Autowired
private MessageChannel mqttOutboundChannel;
public void sendMessage(String topic, String payload) {
MqttPahoMessageHandler messageHandler = new MqttPahoMessageHandler("publish", mqttClientFactory);
messageHandler.setAsync(true);
messageHandler.setDefaultTopic(topic);
messageHandler.afterPropertiesSet();
Message<String> message = MessageBuilder.withPayload(payload).build();
mqttOutboundChannel.send(message);
}
}
```
5. 使用MQTT消息接收和发送服务
在需要接收和发送消息的地方，调用`MqttMessageService`和`MqttOutboundMessageService`的方法：
```java
@Autowired
private MqttMessageService mqttMessageService;
@Autowired
private MqttOutboundMessageService mqttOutboundMessageService;
public void someMethod() {
String topic = "your_topic";
String payload = "your_payload";
mqttMessageService.receiveMessage(topic, payload);
mqttOutboundMessageService.sendMessage(topic, payload);
}
```
这样，就可以使用Spring Boot和MQTT协议来收发消息了。
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