如何避免 Spring Cloud Dataflow Source 应用程序不断返回相同的消息

Question

我正在订阅 rabbitMQ 服务器上的队列并使用其上的消息来检索正文和一个特定的 header。这是在 Spring 云数据流源应用程序上完成的，问题是当它启动时它会继续执行并返回最后一条消息。 我需要添加什么才能使应用程序仅在新消息到达正在侦听的队列时执行？

这是我的供应商代码：

@Log4j2
@EnableConfigurationProperties({ RabbitMQProperties.class })
@Configuration
public class ReceiveMessageConfiguration {
    private final static String QUEUE_NAME = "UniversalId";
    String payload;
    Connection connection;
    Channel channel;


    @Bean
    public Supplier<String> receiverMessage(RabbitMQProperties rabbitMQProperties) throws Exception {
        return () -> {
            try {
                ConnectionFactory factory = new ConnectionFactory();
                factory.setHost("localhost");
                factory.setRequestedHeartbeat(0);

                connection = factory.newConnection();
                channel = connection.createChannel();

                channel.queueDeclare(QUEUE_NAME, true, false, false, null);

                DeliverCallback deliverCallback = (consumerTag, delivery) -> {
                    String message = new String(delivery.getBody(), StandardCharsets.UTF_8);
//              Get headers from properties
                    AMQP.BasicProperties properties = delivery.getProperties();
                    Map<String, Object> headers = properties.getHeaders();

//              Extract and print payload and header
                    for (Map.Entry<String, Object> header : headers.entrySet()) {
                        if (header.getKey().toString().equals("UniversalId")) {
//                      log.info("ID nedeed: " + header.getValue());
                        }
                    }
                    payload = message;
                };
                channel.basicConsume(QUEUE_NAME, true, deliverCallback, consumerTag -> {
                });
                log.info(payload);
                if (payload != null) {
                    return payload;
                }

            } catch (Exception e) {
                e.printStackTrace();
            } finally {

                try {
                    channel.close();
                    connection.close();
                } catch (IOException | TimeoutException e) {
                    e.printStackTrace();
                }
            }
            return new String("No message");

        };
    }
}

我的属性文件是这样的：

spring.cloud.stream.function.bindings.receiverMessage-in-0=input
spring.cloud.stream.function.bindings.receiverMessage-out-0=output
spring.cloud.stream.bindings.input.destination=receiverMessage-input
spring.cloud.stream.bindings.output.destination=receiverMessage-output

更新：这是控制台消息的示例：

2022-12-21T16:25:19.725-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[           main][0;39m [36mm.c.n.r.RabbitMqCustomSourceApplication [0;39m [2m:[0;39m Started RabbitMqCustomSourceApplication in 7.888 seconds (process running for 9.482)
[2m2022-12-21T16:25:20.432-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:21.478-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:22.523-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:23.568-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:24.604-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:25.913-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:27.056-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:28.124-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m null
[2m2022-12-21T16:25:29.167-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m [
    {
        "MailRequest": {
            "action": "fourth",
            "mails": []
        }
    }
]
[2m2022-12-21T16:25:30.233-06:00[0;39m [32m INFO[0;39m [35m21600[0;39m [2m---[0;39m [2m[   scheduling-1][0;39m [36mm.c.n.r.s.ReceiveMessageConfiguration   [0;39m [2m:[0;39m [
    {
        "MailRequest": {
            "action": "fourth",
            "mails": []
        }
    }
]

我已经尝试将 RabbitMQ API 更改为 AMQP API，但行为是相同的。

Answer 1

乳晕，

因为这是直接使用 Rabbit/AMQP 的自定义函数，所以 SCDF 没有影响。 因此，这更像是一个 Rabbit/AMQP 问题。

此外，您可能想看看RabbitSource提供的应用程序，它可以作为替代品。

Answer 2

首先，我要感谢@onobc 的指导。 为了结束这个问题，我使用带有有效负载的转换处理器默认应用程序和 SPeL 表达式来提取特定标头，如下所示： - -expression="new String(headers.get('LoggerID') + payload) 。其中 LoggerID 是您要提取的 header 的名称。