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批量消息

批量发送可以提⾼发送性能，但有⼀定的限制：
topic 相同
waitStoreMsgOK 相同 （⾸先我们建设消息的iswaitstoremsgok=true(默认为true), 如果没有异常,我们将始终收到"OK"，org.apache.rocketmq.common.message.Message#isWaitStoreMsgOK）
不支持延时发送
⼀批消息的大小不能⼤于 4M(DefaultMQProducer.maxMessageSize)
大小限制需要特殊注意，因为消息是动态的，不注意的话就可能超限，就会报错：
计算消息的大小
= (topic + body + （key + value) * N) * 吞吐量

int tmpSize = message.getTopic().length() + message.getBody().length;
Map<String, String> properties = message.getProperties();
for (Map.Entry<String, String> entry : properties.entrySet()) {tmpSize += entry.getKey().length() + entry.getValue().length();
}

BatchProducer.java

package com.example.rocketmq.demo.batch;import org.apache.rocketmq.client.producer.DefaultMQProducer;
import org.apache.rocketmq.client.producer.SendResult;
import org.apache.rocketmq.common.message.Message;import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;public class BatchProducer {public static void main(String[] args) throws Exception {//Instantiate with a producer group name.DefaultMQProducer producer = newDefaultMQProducer("please_rename_unique_group_name");// Specify name server addresses.producer.setNamesrvAddr("localhost:9876");//Launch the instance.producer.start();String topic = "TopicTest";List<Message> messages = new ArrayList<>();messages.add(new Message(topic, "TagA", "OrderID001", "Hello world 0".getBytes()));messages.add(new Message(topic, "TagA", "OrderID002", "Hello world 1".getBytes()));messages.add(new Message(topic, "TagA", "OrderID003", "Hello world 2".getBytes()));//then you could split the large list into small ones:ListSplitter splitter = new ListSplitter(messages);while (splitter.hasNext()) {try {List<Message>  listItem = splitter.next();SendResult sendResult = producer.send(listItem);System.out.printf("%s%n", sendResult);} catch (Exception e) {e.printStackTrace();//handle the error}}//Shut down once the producer instance is not longer in use.producer.shutdown();}
}class ListSplitter implements Iterator<List<Message>> {private final int SIZE_LIMIT = 1024 * 1024 * 4;private final List<Message> messages;private int currIndex;public ListSplitter(List<Message> messages) {this.messages = messages;}@Override public boolean hasNext() {return currIndex < messages.size();}@Override public List<Message> next() {int nextIndex = currIndex;int totalSize = 0;for (; nextIndex < messages.size(); nextIndex++) {Message message = messages.get(nextIndex);//计算消息的大小 = (topic + body + （key + value) * N) * 吞吐量int tmpSize = message.getTopic().length() + message.getBody().length;//属性值的添加Map<String, String> properties = message.getProperties();for (Map.Entry<String, String> entry : properties.entrySet()) {//+key + valuetmpSize += entry.getKey().length() + entry.getValue().length();}tmpSize = tmpSize + 20; //for log overheadif (tmpSize > SIZE_LIMIT) {//it is unexpected that single message exceeds the SIZE_LIMIT//here just let it go, otherwise it will block the splitting processif (nextIndex - currIndex == 0) {//if the next sublist has no element, add this one and then break, otherwise just breaknextIndex++;}break;}if (tmpSize + totalSize > SIZE_LIMIT) {break;} else {totalSize += tmpSize;}}List<Message> subList = messages.subList(currIndex, nextIndex);currIndex = nextIndex;return subList;}
}

BatchConsumer.java

package com.example.rocketmq.demo.batch;import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;
import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;
import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;
import org.apache.rocketmq.client.consumer.listener.MessageListenerConcurrently;
import org.apache.rocketmq.client.exception.MQClientException;
import org.apache.rocketmq.common.message.MessageExt;import java.util.List;public class BatchConsumer {public static void main(String[] args) throws InterruptedException, MQClientException {// Instantiate with specified consumer group name.DefaultMQPushConsumer consumer = new DefaultMQPushConsumer("please_rename_unique_group_name");// Specify name server addresses.consumer.setNamesrvAddr("localhost:9876");// Subscribe one more more topics to consume.consumer.subscribe("TopicTest", "*");// Register callback to execute on arrival of messages fetched from brokers.consumer.registerMessageListener(new MessageListenerConcurrently() {@Overridepublic ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,ConsumeConcurrentlyContext context) {System.out.printf("%s Receive New Messages: %s %n", Thread.currentThread().getName(), msgs);return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;}});//Launch the consumer instance.consumer.start();System.out.printf("Consumer Started.%n");}
}