POP 消费模式的说明

<dependencies>
        <dependency>
            <groupId>org.apache.rocketmq</groupId>
            <artifactId>rocketmq-client-java</artifactId>
            <version>5.0.6</version>
        </dependency>
</dependencies>

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.rocketmq.client.java.example;

import java.time.Duration;
import java.util.Collections;
import java.util.List;
import org.apache.rocketmq.client.apis.ClientConfiguration;
import org.apache.rocketmq.client.apis.ClientException;
import org.apache.rocketmq.client.apis.ClientServiceProvider;
import org.apache.rocketmq.client.apis.SessionCredentialsProvider;
import org.apache.rocketmq.client.apis.StaticSessionCredentialsProvider;
import org.apache.rocketmq.client.apis.consumer.FilterExpression;
import org.apache.rocketmq.client.apis.consumer.FilterExpressionType;
import org.apache.rocketmq.client.apis.consumer.SimpleConsumer;
import org.apache.rocketmq.client.apis.message.MessageId;
import org.apache.rocketmq.client.apis.message.MessageView;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class SimpleConsumerExample {
    private static final Logger log = LoggerFactory.getLogger(SimpleConsumerExample.class);

    private SimpleConsumerExample() {
    }

    @SuppressWarnings({"resource", "InfiniteLoopStatement"})
    public static void main(String[] args) throws ClientException {
        final ClientServiceProvider provider = ClientServiceProvider.loadService();

        // Credential provider is optional for client configuration.
        String accessKey = "用户ak";
        String secretKey = "用户sk";
        SessionCredentialsProvider sessionCredentialsProvider =
            new StaticSessionCredentialsProvider(accessKey, secretKey);

        String endpoints = "腾讯云页面接入点";
        ClientConfiguration clientConfiguration = ClientConfiguration.newBuilder()
            .setEndpoints(endpoints)
            // On some Windows platforms, you may encounter SSL compatibility issues. Try turning off the SSL option in
            // client configuration to solve the problem please if SSL is not essential.
            // .enableSsl(false)
            .setCredentialProvider(sessionCredentialsProvider)
            .build();
        String consumerGroup = "消费组";
        // 默认消费时间，30s，也就是说，对于拉到的消息，30s内如果消费没完成，该条消息会被别的客户端重新拉到，
        // 需要用户根据自己的场景配置
        Duration awaitDuration = Duration.ofSeconds(30);
        String tag = "*";
        String topic = "topic名字";
        FilterExpression filterExpression = new FilterExpression(tag, FilterExpressionType.TAG);
        // In most case, you don't need to create too many consumers, singleton pattern is recommended.
        SimpleConsumer consumer = provider.newSimpleConsumerBuilder()
            .setClientConfiguration(clientConfiguration)
            // Set the consumer group name.
            .setConsumerGroup(consumerGroup)
            // set await duration for long-polling.
            .setAwaitDuration(awaitDuration)
            // Set the subscription for the consumer.
            .setSubscriptionExpressions(Collections.singletonMap(topic, filterExpression))
            .build();
        // Max message num for each long polling.
        int maxMessageNum = 16;
        // Set message invisible duration after it is received.
        Duration invisibleDuration = Duration.ofSeconds(15);
        // Receive message, multi-threading is more recommended.
        do {
            final List<MessageView> messages = consumer.receive(maxMessageNum, invisibleDuration);
            log.info("Received {} message(s)", messages.size());
            for (MessageView message : messages) {
                final MessageId messageId = message.getMessageId();
                try {
                    consumer.ack(message);
                    log.info("Message is acknowledged successfully, messageId={}", messageId);
                } catch (Throwable t) {
                    log.error("Message is failed to be acknowledged, messageId={}", messageId, t);
                }
            }
        } while (true);
        // Close the simple consumer when you don't need it anymore.
        // You could close it manually or add this into the JVM shutdown hook.
        // consumer.close();
    }
}