このトピックでは、HTTPクライアントSDK for Javaを使用して、スケジュールされたメッセージと遅延されたメッセージを送受信する方法に関するサンプルコードを提供します。
の背景情報
遅延メッセージは、特定の期間後にApsaraMQ for RocketMQブローカーによってコンシューマに配信されるメッセージです。
スケジュールされたメッセージは、ApsaraMQ for RocketMQブローカーが特定の時点でコンシューマに配信するメッセージです。
スケジュールされたメッセージのコード構成は、HTTP上の遅延メッセージのコード構成と同じです。 どちらのタイプのメッセージも、メッセージの属性に基づいて特定の期間後にコンシューマに配信されます。
詳細については、「スケジュールされたメッセージと遅延メッセージ」をご参照ください。
の前提条件
開始する前に、次の操作が実行されていることを確認してください。
SDK for Javaをインストールします。 詳細については、「環境の準備」をご参照ください。
ApsaraMQ for RocketMQコンソールのコードで指定するリソースを作成します。 リソースには、インスタンス、トピック、および消費者グループが含まれます。 詳細については、「リソースの作成」 をご参照ください。
Alibaba CloudアカウントのAccessKeyペアを取得します。 詳細については、「AccessKey の作成」をご参照ください。
スケジュールされたメッセージと遅延メッセージの送信
次のサンプルコードは、Java用HTTPクライアントSDKを使用して、スケジュールされたメッセージと遅延されたメッセージを送信する方法の例を示しています。
import com.aliyun.mq.http.MQClient;
import com.aliyun.mq.http.MQProducer;
import com.aliyun.mq.http.model.TopicMessage;
import java.util.Date;
public class Producer {
public static void main(String[] args) {
MQClient mqClient = new MQClient(
// The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console.
"${HTTP_ENDPOINT}",
// Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured.
// The AccessKey ID that is used for authentication.
System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),
// The AccessKey secret that is used for authentication.
System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
);
// The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console.
// Each topic can be used to send and receive messages of one specific type. For example, a topic that is used to send and receive normal messages cannot be used to send or receive messages of other types.
final String topic = "${TOPIC}";
// The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console.
// If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console.
final String instanceId = "${INSTANCE_ID}";
// Obtain the producer that sends messages to the topic.
MQProducer producer;
if (instanceId != null && instanceId != "") {
producer = mqClient.getProducer(instanceId, topic);
} else {
producer = mqClient.getProducer(topic);
}
try {
// Cyclically send four messages.
for (int i = 0; i < 4; i++) {
TopicMessage pubMsg;
pubMsg = new TopicMessage(
// The message content.
"hello mq!".getBytes(),
// The message tag.
"A"
);
// The custom attributes of the message.
pubMsg.getProperties().put("a", String.valueOf(i));
// The message key.
pubMsg.setMessageKey("MessageKey");
// The period of time after which the broker delivers the message to the consumer. In this example, the broker delivers the message to the consumer after a delay of 10 seconds. Set this parameter to a timestamp in milliseconds.
// If the producer sends a scheduled message, set the parameter to the time difference between the scheduled point in time and the current point in time.
pubMsg.setStartDeliverTime(System.currentTimeMillis() + 10 * 1000);
// Send the message in synchronous transmission mode. If no exception is thrown, the message is sent.
TopicMessage pubResultMsg = producer.publishMessage(pubMsg);
// Send the message in synchronous transmission mode. If no exception is thrown, the message is sent.
System.out.println(new Date() + " Send mq message success. Topic is:" + topic + ", msgId is: " + pubResultMsg.getMessageId()
+ ", bodyMD5 is: " + pubResultMsg.getMessageBodyMD5());
}
} catch (Throwable e) {
// The logic that you want to use to resend or persist the message if the message fails to be sent and needs to be sent again.
System.out.println(new Date() + " Send mq message failed. Topic is:" + topic);
e.printStackTrace();
}
mqClient.close();
}
}定期メッセージと遅延メッセージの購読
次のサンプルコードは、Java用HTTPクライアントSDKを使用して、スケジュールされたメッセージまたは遅延したメッセージをサブスクライブする方法の例を示しています。
import com.aliyun.mq.http.MQClient;
import com.aliyun.mq.http.MQConsumer;
import com.aliyun.mq.http.common.AckMessageException;
import com.aliyun.mq.http.model.Message;
import java.util.ArrayList;
import java.util.List;
public class Consumer {
public static void main(String[] args) {
MQClient mqClient = new MQClient(
// The HTTP endpoint. You can obtain the endpoint in the HTTP Endpoint section of the Instance Details page in the ApsaraMQ for RocketMQ console.
"${HTTP_ENDPOINT}",
// Make sure that the environment variables ALIBABA_CLOUD_ACCESS_KEY_ID and ALIBABA_CLOUD_ACCESS_KEY_SECRET are configured.
// The AccessKey ID that is used for authentication.
System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID"),
// The AccessKey secret that is used for authentication.
System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET")
);
// The topic in which the message is produced. You must create the topic in the ApsaraMQ for RocketMQ console.
// Each topic can be used to send and receive messages of a specific type. For example, a topic that is used to send and receive normal messages cannot be used to send or receive messages of other types.
final String topic = "${TOPIC}";
// The ID of the consumer group that you created in the ApsaraMQ for RocketMQ console.
final String groupId = "${GROUP_ID}";
// The ID of the instance to which the topic belongs. You must create the instance in the ApsaraMQ for RocketMQ console.
// If the instance has a namespace, specify the ID of the instance. If the instance does not have a namespace, set the instanceID parameter to null or an empty string. You can obtain the namespace of the instance on the Instance Details page in the ApsaraMQ for RocketMQ console.
final String instanceId = "${INSTANCE_ID}";
final MQConsumer consumer;
if (instanceId != null && instanceId != "") {
consumer = mqClient.getConsumer(instanceId, topic, groupId, null);
} else {
consumer = mqClient.getConsumer(topic, groupId);
}
// Cyclically consume messages in the current thread. We recommend that you use multiple threads to concurrently consume messages.
do {
List<Message> messages = null;
try {
// Consume messages in long polling mode.
// In long polling mode, if no message in the topic is available for consumption, the request is suspended on the broker for the specified period of time. If a message becomes available for consumption within the specified period of time, the broker immediately sends a response to the consumer. In this example, the value is specified as 3 seconds.
messages = consumer.consumeMessage(
3,// Specify the maximum number of messages that can be consumed at a time. In this example, the value is specified as 3. The maximum value that you can specify is 16.
3// The duration of a long polling cycle. Unit: seconds. In this example, the value is specified as 3. The maximum value you can specify is 30.
);
} catch (Throwable e) {
e.printStackTrace();
try {
Thread.sleep(2000);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
}
// No message in the topic is available for consumption.
if (messages == null || messages.isEmpty()) {
System.out.println(Thread.currentThread().getName() + ": no new message, continue!");
continue;
}
// The message consumption logic.
for (Message message : messages) {
System.out.println("Receive message: " + message);
}
// If the broker does not receive an acknowledgment (ACK) for a message from the consumer before the delivery retry interval elapses, the broker sends the message for consumption again.
// A unique timestamp is specified for the handle of a message each time the message is consumed.
{
List<String> handles = new ArrayList<String>();
for (Message message : messages) {
handles.add(message.getReceiptHandle());
}
try {
consumer.ackMessage(handles);
} catch (Throwable e) {
// If the handle of a message times out, the broker cannot receive an ACK for the message from the consumer.
if (e instanceof AckMessageException) {
AckMessageException errors = (AckMessageException) e;
System.out.println("Ack message fail, requestId is:" + errors.getRequestId() + ", fail handles:");
if (errors.getErrorMessages() != null) {
for (String errorHandle :errors.getErrorMessages().keySet()) {
System.out.println("Handle:" + errorHandle + ", ErrorCode:" + errors.getErrorMessages().get(errorHandle).getErrorCode()
+ ", ErrorMsg:" + errors.getErrorMessages().get(errorHandle).getErrorMessage());
}
}
continue;
}
e.printStackTrace();
}
}
} while (true);
}
}