spring boot coap

Spring Boot提供了对CoAP（Constrained Application Protocol）的支持。CoAP是一种专门用于物联网设备的轻量级通信协议，它可以在低带宽和网络带宽受限的环境下工作。

要使用Spring Boot与CoAP进行通信，你需要添加Spring Boot的CoAP依赖项。可以通过在Maven或Gradle构建文件中添加以下依赖项来实现：

Maven：

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-integration</artifactId>
</dependency>
<dependency>
    <groupId>org.eclipse.californium</groupId>
    <artifactId>californium-core</artifactId>
    <version>2.0.0-M7</version>
</dependency>

Gradle：

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-integration'
    implementation 'org.eclipse.californium:californium-core:2.0.0-M7'
}

添加依赖项后，你可以通过创建一个CoapServer实例来启动一个CoAP服务器，并使用CoapClient实例与CoAP服务器进行通信。以下是一个简单的示例：

import org.eclipse.californium.core.CoapServer;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.integration.annotation.IntegrationComponentScan;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.coap.CoapHeaders;
import org.springframework.integration.coap.inbound.CoapInboundGateway;
import org.springframework.integration.coap.outbound.CoapOutboundGateway;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.IntegrationFlows;
import org.springframework.integration.ip.dsl.Tcp;
import org.springframework.messaging.Message;
import org.springframework.messaging.MessageChannel;

@SpringBootApplication
@IntegrationComponentScan
public class CoapApplication {

    public static void main(String[] args) {
        SpringApplication.run(CoapApplication.class, args);
    }

    @Bean
    public CoapServer coapServer() {
        CoapServer coapServer = new CoapServer();
        coapServer.add(new HelloWorldResource());
        return coapServer;
    }

    @Bean
    public IntegrationFlow coapInboundFlow() {
        return IntegrationFlows.from(coapInboundGateway())
                .channel(coapRequestChannel())
                .handle("myService", "handleCoapMessage")
                .channel(coapResponseChannel())
                .handle(coapOutboundGateway())
                .get();
    }

    @Bean
    public CoapInboundGateway coapInboundGateway() {
        CoapInboundGateway coapInboundGateway = new CoapInboundGateway();
        coapInboundGateway.setRequestChannel(coapRequestChannel());
        coapInboundGateway.setPath("/hello");
        return coapInboundGateway;
    }

    @Bean
    public MessageChannel coapRequestChannel() {
        return new DirectChannel();
    }

    @Bean
    public MessageChannel coapResponseChannel() {
        return new DirectChannel();
    }

    @Bean
    public CoapOutboundGateway coapOutboundGateway() {
        CoapOutboundGateway coapOutboundGateway = new CoapOutboundGateway("coap://localhost/hello");
        coapOutboundGateway.setOutputChannel(coapResponseChannel());
        return coapOutboundGateway;
    }

    @Bean
    public MyService myService() {
        return new MyService();
    }

    public static class HelloWorldResource extends CoapResource {
        public HelloWorldResource() {
            super("hello");
        }

        @Override
        public void handleGET(CoapExchange exchange) {
            exchange.respond("Hello, world!");
        }
    }

    public static class MyService {
        @ServiceActivator
        public Message<String> handleCoapMessage(Message<?> message) {
            String payload = message.getPayload().toString();
            String path = message.getHeaders().get(CoapHeaders.PATH).toString();
            System.out.println("Received CoAP message with payload: " + payload + ", path: " + path);
            return new GenericMessage<>("Hello, world!");
        }
    }

    @MessagingGateway(defaultRequestChannel = "coapRequestChannel")
    public interface CoapClient {
        @Tcp(host = "localhost", port = 5683)
        String send(String payload);
    }
}

在上面的示例中，我们创建了一个CoapServer实例，并将其添加到一个名为“hello”的CoAP资源中。该资源响应GET请求并返回“Hello, world!”字符串。

我们还创建了一个名为“myService”的Spring Bean，并在其中声明了一个@ServiceActivator方法，该方法接收一个CoAP消息并返回一个响应消息。

我们创建了一个CoapInboundGateway实例来接收来自CoAP客户端的请求，并将其转换为Spring Integration消息。我们还创建了一个CoapOutboundGateway实例，用于向CoAP服务器发送请求并将其转换为Spring Integration消息。

最后，我们创建了一个名为“CoapClient”的Spring集成MessagingGateway，用于向CoAP服务器发送请求。通过调用CoapClient的send方法，我们可以向CoAP服务器发送请求并获取响应。

这是一个简单的示例，演示了如何使用Spring Boot与CoAP进行通信。你可以根据需要进行更改和扩展，以满足你的具体需求。