Java可以通过MQTT协议来连接emqx服务器,并通过订阅、发布消息等操作来控制emqx服务器。下面是Java操作emqx的示例代码:
javaString broker = "tcp://localhost:1883";
String clientId = "Java_Client";
MemoryPersistence persistence = new MemoryPersistence();
MqttClient client = new MqttClient(broker, clientId, persistence);
MqttConnectOptions connOpts = new MqttConnectOptions();
connOpts.setCleanSession(true);
//connect to the broker
client.connect(connOpts);
javaString topic = "test/topic";
int qos = 2;
client.subscribe(topic, qos);
javaString topic = "test/topic";
String content = "Hello, emqx!";
int qos = 2;
MqttMessage message = new MqttMessage(content.getBytes());
message.setQos(qos);
client.publish(topic, message);
通过以上操作,我们可以很方便地使用Java来控制emqx服务器。
实现了一个简单的MQTT消息发送和订阅功能,可以用来操作emqx服务器。
使用IDEA或其他编辑器创建一个新的Spring Boot项目,选择Web和Thymeleaf等依赖。具体的依赖配置如下:
xml<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.integration</groupId>
<artifactId>spring-integration-stream</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.integration</groupId>
<artifactId>spring-integration-mqtt</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
其中,使用spring-integration-mqtt依赖来实现MQTT客户端的功能。
在application.properties文件中添加MQTT相关配置:
spring.mqtt.username=user spring.mqtt.password=passwd spring.mqtt.url=tcp://localhost:1883 # 客户端ID,建议使用唯一的字符串 spring.mqtt.client-id=client-1 # 订阅的主题 spring.mqtt.default-topic=test/topic
创建MQTT的配置类,并设置连接参数和订阅主题:
java@Configuration
@EnableMqtt
public class MqttConfig {
@Autowired
private MqttPahoMessageDrivenChannelAdapter mqttAdapter;
@Bean
public MqttConnectOptions mqttConnectOptions() {
MqttConnectOptions mqttConnectOptions = new MqttConnectOptions();
mqttConnectOptions.setUserName("${spring.mqtt.username}");
mqttConnectOptions.setPassword("${spring.mqtt.password}".toCharArray());
mqttConnectOptions.setServerURIs(new String[]{ "${spring.mqtt.url}" });
return mqttConnectOptions;
}
@ServiceActivator(inputChannel = "mqttInputChannel")
public void messageReceiver(String message) {
System.out.println("Received message: " + message);
}
@Bean
public MessageChannel mqttInputChannel() {
return new DirectChannel();
}
@Bean
public IntegrationFlow mqttInFlow() {
return IntegrationFlows
.from(mqttAdapter)
.channel(mqttInputChannel())
.get();
}
@Bean
public MqttPahoClientFactory mqttClientFactory() {
DefaultMqttPahoClientFactory factory = new DefaultMqttPahoClientFactory();
factory.setConnectionOptions(mqttConnectOptions());
return factory;
}
@Bean
public MqttPahoMessageDrivenChannelAdapter mqttAdapter() {
MqttPahoMessageDrivenChannelAdapter adapter =
new MqttPahoMessageDrivenChannelAdapter("${spring.mqtt.client-id}",
mqttClientFactory(),
"${spring.mqtt.default-topic}");
adapter.setCompletionTimeout(5000);
adapter.setConverter(new DefaultPahoMessageConverter());
adapter.setQos(1);
return adapter;
}
}
其中,mqttConnectOptions方法用来设置MQTT连接的参数,messageReceiver方法用来接收MQTT消息,mqttInputChannel和mqttInFlow用来配置MQTT消息的输入流。mqttClientFactory方法用来创建MQTT客户端,mqttAdapter用来设置MQTT的相关参数。
创建MQTT服务类,用来实现MQTT客户端的连接、消息的发送和订阅等操作:
java@Service
public class MqttService {
@Autowired
private MqttPahoMessageHandler mqttHandler;
@Autowired
private MqttAdapter mqttAdapter;
public void sendMessage(String topic, String message) {
MqttMessage mqttMessage = new MqttMessage();
mqttMessage.setPayload(message.getBytes());
mqttMessage.setQos(1);
mqttMessage.setRetained(false);
mqttHandler.handleMessage(new Message<byte[]>(mqttMessage.getPayload(), new MessageHeaders(Collections.singletonMap(MqttHeaders.TOPIC, topic))));
}
public void subscribe(String topic) {
mqttAdapter.addTopic(topic);
}
}
其中,sendMessage方法用来发送MQTT消息,subscribe方法用来订阅MQTT主题。
创建一个MqttController控制器,用来处理MQTT相关的请求:
java@RestController
@RequestMapping("/mqtt")
public class MqttController {
@Autowired
private MqttService mqttService;
@GetMapping("/subscribe")
public String subscribe(String topic) {
mqttService.subscribe(topic);
return "订阅成功";
}
@PostMapping("/send")
public String sendMessage(String topic, String message) {
mqttService.sendMessage(topic, message);
return "发送成功";
}
}
其中,subscribe方法处理订阅MQTT主题的请求,sendMessage方法处理发送MQTT消息的请求。
最后,创建页面,用来测试订阅和发送MQTT消息。这里省略具体页面代码。
至此,一个完整的Spring Boot项目就完成了,它可以实现订阅MQTT主题和发送MQTT消息的功能,可以用来操作emqx服务器。