Java技術棧
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作者：海向
來源：www.cnblogs.com/haixiang/p/10826710.html
RabbitMQ 簡述
簡單隊列
簡單隊列是最簡單的一種模式，由生產者、隊列、消費者組成。生產者將消息發送給隊列，消費者從隊列中讀取消息完成消費。關注公衆號Java技術棧回覆：面試，可以獲取我整理的 RabbitMQ 系列面試題，帶全部答案。
在下圖中，“P”是我們的生產者，“C”是我們的消費者。中間的框是隊列 - RabbitMQ代表消費者的消息緩衝區。
Java 方式
生產者
package com.anqi.mq.nat;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.ConnectionFactory;
public class MyProducer {
private static final String QUEUE_NAME = "ITEM_QUEUE";
public static void main(String[] args) throws Exception {
//1. 創建一個 ConnectionFactory 並進行設置
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setVirtualHost("/");
factory.setUsername("guest");
factory.setPassword("guest");
//2. 通過連接工廠來創建連接
Connection connection = factory.newConnection();
//3. 通過 Connection 來創建 Channel
Channel channel = connection.createChannel();
//實際場景中，消息多爲json格式的對象
String msg = "hello";
//4. 發送三條數據
for (int i = 1; i <= 3 ; i++) {
channel.basicPublish("", QUEUE_NAME, null, msg.getBytes());
System.out.println("Send message" + i +" : " + msg);
}
//5. 關閉連接
channel.close();
connection.close();
}
}
/**
* Declare a queue
* @param queue the name of the queue
* @param durable true if we are declaring a durable queue (the queue will survive a server restart)
* @param exclusive true if we are declaring an exclusive queue (restricted to this connection)
* @param autoDelete true if we are declaring an autodelete queue (server will delete it when no longer in use)
* @param arguments other properties (construction arguments) for the queue
* @return a declaration-confirm method to indicate the queue was successfully declared
* @throws java.io.IOException if an error is encountered
*/
Queue.DeclareOk queueDeclare(String queue, boolean durable, boolean exclusive, boolean autoDelete,Map<String, Object> arguments) throws IOException;
/**
* Publish a message
* @see com.rabbitmq.client.AMQP.Basic.Publish
* @param exchange the exchange to publish the message to
* @param routingKey the routing key
* @param props other properties for the message - routing headers etc
* @param body the message body
* @throws java.io.IOException if an error is encountered
*/
void basicPublish(String exchange, String routingKey, BasicProperties props, byte[] body) throws IOException;
/**
* Start a non-nolocal, non-exclusive consumer, with
* a server-generated consumerTag.
* @param queue the name of the queue
* @param autoAck true if the server should consider messages
* acknowledged once delivered; false if the server should expect
* explicit acknowledgements
* @param callback an interface to the consumer object
* @return the consumerTag generated by the server
* @throws java.io.IOException if an error is encountered
* @see com.rabbitmq.client.AMQP.Basic.Consume
* @see com.rabbitmq.client.AMQP.Basic.ConsumeOk
* @see #basicConsume(String, boolean, String, boolean, boolean, Map, Consumer)
*/
String basicConsume(String queue, boolean autoAck, Consumer callback) throws IOException;
消費者
package com.anqi.mq.nat;
import com.rabbitmq.client.*;
import java.io.IOException;
public class MyConsumer {
private static final String QUEUE_NAME = "ITEM_QUEUE";
public static void main(String[] args) throws Exception {
//1. 創建一個 ConnectionFactory 並進行設置
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
factory.setVirtualHost("/");
factory.setUsername("guest");
factory.setPassword("guest");
//2. 通過連接工廠來創建連接
Connection connection = factory.newConnection();
//3. 通過 Connection 來創建 Channel
Channel channel = connection.createChannel();
//4. 聲明一個隊列
channel.queueDeclare(QUEUE_NAME, true, false, false, null);
System.out.println(" [*] Waiting for messages. To exit press CTRL+C");
/*
true:表示自動確認，只要消息從隊列中獲取，無論消費者獲取到消息後是否成功消費，都會認爲消息已經成功消費
false:表示手動確認，消費者獲取消息後，服務器會將該消息標記爲不可用狀態，等待消費者的反饋，如果消費者一
直沒有反饋，那麼該消息將一直處於不可用狀態，並且服務器會認爲該消費者已經掛掉，不會再給其發送消息，
直到該消費者反饋。
*/
//5. 創建消費者並接收消息
Consumer consumer = new DefaultConsumer(channel) {
@Override
public void handleDelivery(String consumerTag, Envelope envelope,
AMQP.BasicProperties properties, byte[] body)
throws IOException {
String message = new String(body, "UTF-8");
System.out.println(" [x] Received '" + message + "'");
}
};
//6. 設置 Channel 消費者綁定隊列
channel.basicConsume(QUEUE_NAME, true, consumer);
}
}
Send message1 : hello
Send message2 : hello
Send message3 : hello
[*] Waiting for messages. To exit press CTRL+C
[x] Received 'hello'
[x] Received 'hello'
[x] Received 'hello'
當我們啓動生產者之後查看RabbitMQ管理後臺可以看到有一條消息正在等待被消費。
當我們啓動消費者之後再次查看，可以看到積壓的一條消息已經被消費。
總結
隊列聲明queueDeclare的參數：第一個參數表示隊列名稱、第二個參數爲是否持久化（true表示是，隊列將在服務器重啓時生存）、第三個參數爲是否是獨佔隊列（創建者可以使用的私有隊列，斷開後自動刪除）、第四個參數爲當所有消費者客戶端連接斷開時是否自動刪除隊列、第五個參數爲隊列的其他參數。
basicConsume的第二個參數autoAck: 應答模式，true：自動應答，即消費者獲取到消息，該消息就會從隊列中刪除掉，false：手動應答，當從隊列中取出消息後，需要程序員手動調用方法應答，如果沒有應答，該消息還會再放進隊列中，就會出現該消息一直沒有被消費掉的現象。
這種簡單隊列的模式，系統會爲每個隊列隱式地綁定一個默認交換機，交換機名稱爲" (AMQP default)"，類型爲直連 direct，當你手動創建一個隊列時，系統會自動將這個隊列綁定到一個名稱爲空的 Direct 類型的交換機上，綁定的路由鍵 routing key 與隊列名稱相同，相當於channel.queueBind(queue:"QUEUE_NAME", exchange:"(AMQP default)“, routingKey:"QUEUE_NAME");雖然實例沒有顯式聲明交換機，但是當路由鍵和隊列名稱一樣時，就會將消息發送到這個默認的交換機中。這種方式比較簡單，但是無法滿足複雜的業務需求，所以通常在生產環境中很少使用這種方式。
The default exchange is implicitly bound to every queue, with a routing key equal to the queue name. It is not possible to explicitly bind to, or unbind from the default exchange. It also cannot be deleted.默認交換機隱式綁定到每個隊列，其中路由鍵等於隊列名稱。不可能顯式綁定到，或從缺省交換中解除綁定。它也不能被刪除。
——引自 RabbitMQ 官方文檔
spring-amqp方式
引入 Maven 依賴
<dependency>
<groupId>com.rabbitmq</groupId>
<artifactId>amqp-client</artifactId>
<version>5.6.0</version>
</dependency>
<dependency>
<groupId>org.springframework.amqp</groupId>
<artifactId>spring-rabbit</artifactId>
<version>2.1.5.RELEASE</version>
</dependency>
Spring Boot 學習教程：
https://github.com/javastacks/spring-boot-best-practice
Spring 配置文件
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:rabbit="http://www.springframework.org/schema/rabbit"
xsi:schemaLocation="http://www.springframework.org/schema/rabbit
https://www.springframework.org/schema/rabbit/spring-rabbit.xsd
http://www.springframework.org/schema/beans
https://www.springframework.org/schema/beans/spring-beans.xsd">
<rabbit:connection-factory id="connectionFactory" host="localhost" virtual-host="/"
username="guest" password="guest"/>
<rabbit:template id="amqpTemplate" connection-factory="connectionFactory"/>
<rabbit:admin connection-factory="connectionFactory"/>
<rabbit:queue name="MY-QUEUE"/>
</beans>
使用測試
import org.springframework.amqp.core.AmqpTemplate;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class Main {
public static void main(String[] args) {
ApplicationContext app = new ClassPathXmlApplicationContext("spring/rabbit-context.xml");
AmqpTemplate amqpTemplate = app.getBean(AmqpTemplate.class);
amqpTemplate.convertAndSend("MY-QUEUE", "Item");
String msg = (String) amqpTemplate.receiveAndConvert("MY-QUEUE");
System.out.println(msg);
}
}
參考方法
/**
* Convert a Java object to an Amqp {@link Message} and send it to a specific exchange
* with a specific routing key.
*
* @param exchange the name of the exchange
* @param routingKey the routing key
* @param message a message to send
* @throws AmqpException if there is a problem
*/
void convertAndSend(String exchange, String routingKey, Object message) throws AmqpException;
/**
* Receive a message if there is one from a specific queue and convert it to a Java
* object. Returns immediately, possibly with a null value.
*
* @param queueName the name of the queue to poll
* @return a message or null if there is none waiting
* @throws AmqpException if there is a problem
*/
@Nullable
Object receiveAndConvert(String queueName) throws AmqpException;
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