Azure-Service-Bus：如何访问 processMessage() 函数中的消息？

Question

我对 JAVA 不熟悉，并且在理解一个特定问题方面挣扎了好几天。 我想从 Azure 云接收消息，并且我正在使用 Azure-Service-Bus。

根据azure-service-bus documentation，我已经构建了一个如下所示的java文件：

import com.azure.messaging.servicebus.*;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.Arrays;
import java.util.List;

static String connectionString = "<NAMESPACE CONNECTION STRING>";
static String topicName = "<TOPIC NAME>";    
static String subName = "<SUBSCRIPTION NAME>";

// handles received messages
static void receiveMessages() throws InterruptedException
{
    CountDownLatch countdownLatch = new CountDownLatch(1);

    // Create an instance of the processor through the ServiceBusClientBuilder
    ServiceBusProcessorClient processorClient = new ServiceBusClientBuilder()
        .connectionString(connectionString)
        .processor()
        .topicName(topicName)
        .subscriptionName(subName)
        .processMessage(ServiceBusTopicTest::processMessage)
        .processError(context -> processError(context, countdownLatch))
        .buildProcessorClient();

    System.out.println("Starting the processor");
    processorClient.start();

    TimeUnit.SECONDS.sleep(10);
    System.out.println("Stopping and closing the processor");
    processorClient.close();        
}

private static void processMessage(ServiceBusReceivedMessageContext context) {
    ServiceBusReceivedMessage message = context.getMessage();
    System.out.printf("Processing message. Session: %s, Sequence #: %s. Contents: %s%n", message.getMessageId(),
        message.getSequenceNumber(), message.getBody());
}

private static void processError(ServiceBusErrorContext context, CountDownLatch countdownLatch) {
    System.out.printf("Error when receiving messages from namespace: '%s'. Entity: '%s'%n",
        context.getFullyQualifiedNamespace(), context.getEntityPath());

    if (!(context.getException() instanceof ServiceBusException)) {
        System.out.printf("Non-ServiceBusException occurred: %s%n", context.getException());
        return;
    }

    ServiceBusException exception = (ServiceBusException) context.getException();
    ServiceBusFailureReason reason = exception.getReason();

    if (reason == ServiceBusFailureReason.MESSAGING_ENTITY_DISABLED
        || reason == ServiceBusFailureReason.MESSAGING_ENTITY_NOT_FOUND
        || reason == ServiceBusFailureReason.UNAUTHORIZED) {
        System.out.printf("An unrecoverable error occurred. Stopping processing with reason %s: %s%n",
            reason, exception.getMessage());

        countdownLatch.countDown();
    } else if (reason == ServiceBusFailureReason.MESSAGE_LOCK_LOST) {
        System.out.printf("Message lock lost for message: %s%n", context.getException());
    } else if (reason == ServiceBusFailureReason.SERVICE_BUSY) {
        try {
            // Choosing an arbitrary amount of time to wait until trying again.
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            System.err.println("Unable to sleep for period of time");
        }
    } else {
        System.out.printf("Error source %s, reason %s, message: %s%n", context.getErrorSource(),
            reason, context.getException());
    }
}

public static void main(String[] args) throws InterruptedException {        
    receiveMessages();
}

到目前为止一切正常，来自 Azure 的消息打印在控制台日志中。 尽管如此，我的目标是将消息保存在我想在main() 函数中创建的变量/数组列表中。所以我尝试将processMessage() 函数中的消息返回给main() 函数，但它不起作用，因为它是一个静态void 类。我还尝试创建一个数组列表变量并将其传递给processMessage() 函数，但我没有了解如何在processClient 创建中传递数组列表变量。

我正在使用一个名为 Mendix 的低代码平台，并且想要实现这个自定义 java 代码，并且只是在努力将消息传递到数组列表到 main() 函数。

谁能帮助我或给我一个提示如何解决这个问题？

谢谢， 奥马尔

Answer 1

所以我尝试将 processMessage() 函数中的消息返回给 main() 函数，但它不起作用，因为它是静态 void 类。

既然要获取变量类型或数组列表类型的消息，那么只需将返回类型设置为：

public static void main(String args[]){
    System.out.println("---------This is the returnString()---------");
    System.out.println(returnString());
    System.out.println("---------This is the returnArrayList()---------");
    System.out.println(returnArrayList());
}
public static String returnString(){
    //For example is the message you get.
    String message = "some message";
    return message;
}
public static ArrayList returnArrayList(){
    //For example is the message you get.
    ArrayList<String> arlist = new ArrayList<String>( );
    arlist.add("JAVA");
    arlist.add("Csharp");
    arlist.add("Python");
    arlist.add("Php");
    arlist.add("Android");
    arlist.add("HTML");
    return arlist;
}