二、起航
本章节,柯南君将从几个层面,用官网例子讲解一下RabbitMQ的实操经典程序案例,让大家重新回到经典“Hello
world!”(The simplest thing that does something )时代,RabbitMQ
支持N多种客户端(client),这里无法一一讲解,暂定java client,有时间的情况下,在弥补一下。
事先,先普及一下图标(我们会在下面的事例中,会大量用到,所以先普及一下,便于识别,最终更好理解事例的含义)
1、图标概念
① producting(生产者):在程序中 发送消息的一端,我们暂且称之为 生产者,在这里用“p”表示
② queue(队列):队列是一个邮箱的名字。它住在RabbitMQ。尽管消息流经RabbitMQ和您的应用程序,他们只可以存储在一个队列中。队列是不受任何限制,它可以储存尽可能多的信息(按你兴趣来了),它本质上是一个无限缓冲区。许多生产商可以发送消息到一个队列,许多消费者可以尝试接收数据从一个队列。
③ consuming(消费者):消费者和生产者是对应的,较为相似的意思;在这里,我用“C”表示
2、The Java client library
RabbitMQ 中AMQP这是一个开放的、通用的协议消息。有许多客户AMQP在许多不同的语言。我们将使用提供的Java客户机RabbitMQ。
我们需要下载(Download) client library package,并要核实每个jar包,解压到相应位置,如下图所示:
第一步:点击 http://www.rabbitmq.com/java-client.html,然后找到相应的lib下载位置
第二步:选择合适的下载,比如我下载了zip包,如图所示:
第三步:Unzip it(解压它) 到你的working directory(工作目录)中 and grab (并且获得)你的jar包文件
- $ unzip rabbitmq-java-client-bin-*.zip
- $ cp rabbitmq-java-client-bin-*/*.jar ./
3、程序案例
1) "Hello World"
① sending (发送)
- 在send.java 中,我们需要import一些class ,如下所示:
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
- set up(设置)类和queue的name
public class Send {
private final static String QUEUE_NAME = "hello";
public static void main(String[] argv)
throws java.io.IOException {
...
}
}
- then 我们create 一个connection (连接)到server(服务端)
onnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
- 这个connection 是抽象的socket connection链接;
- 负责协议版本(protocol version negotigation)和身份认证(authentication );
- 我们在本地机器上连接到一个代理即 localhost ,如果我们想要连接到代理不同机器上我们简单的指定其名称或者IP地址即可;
channel.queueDeclare(QUEUE_NAME, false, false, false, null);
String message = "Hello World!";
channel.basicPublish("", QUEUE_NAME, null, message.getBytes());
System.out.println(" [x] Sent '" + message + "'");
channel.close();
connection.close();
import com.rabbitmq.client.ConnectionFactory; import com.rabbitmq.client.Connection; import com.rabbitmq.client.Channel; public class Send { private final static String QUEUE_NAME = "hello"; public static void main(String[] argv) throws Exception { ConnectionFactory factory = new ConnectionFactory(); factory.setHost("localhost"); Connection connection = factory.newConnection(); Channel channel = connection.createChannel(); channel.queueDeclare(QUEUE_NAME, false, false, false, null); String message = "Hello World!"; channel.basicPublish("", QUEUE_NAME, null, message.getBytes()); System.out.println(" [x] Sent '" + message + "'"); channel.close(); connection.close(); } }
② Receiving (接收)
- The code (in Recv.java) has almost the same imports as Send:
import com.rabbitmq.client.ConnectionFactory;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.QueueingConsumer;
public class Recv {
private final static String QUEUE_NAME = "hello";
public static void main(String[] argv)
throws java.io.IOException,
java.lang.InterruptedException {
ConnectionFactory factory = new ConnectionFactory();
factory.setHost("localhost");
Connection connection = factory.newConnection();
Channel channel = connection.createChannel();
channel.queueDeclare(QUEUE_NAME, false, false, false, null);
System.out.println(" [*] Waiting for messages. To exit press CTRL+C");
...
}
}
QueueingConsumer consumer = new QueueingConsumer(channel);
channel.basicConsume(QUEUE_NAME, true, consumer);
while (true) {
QueueingConsumer.Delivery delivery = consumer.nextDelivery();
String message = new String(delivery.getBody());
System.out.println(" [x] Received '" + message + "'");
}
QueueingConsumer.nextDelivery()块,直到另一个来自服务器的消息交付。
下面是Recv.java 源代码:import com.rabbitmq.client.ConnectionFactory;import com.rabbitmq.client.Connection;import com.rabbitmq.client.Channel;import com.rabbitmq.client.QueueingConsumer;public class Recv {private final static String QUEUE_NAME = "hello";public static void main(String[] argv) throws Exception {ConnectionFactory factory = new ConnectionFactory();factory.setHost("localhost");Connection connection = factory.newConnection();Channel channel = connection.createChannel();channel.queueDeclare(QUEUE_NAME, false, false, false, null);System.out.println(" [*] Waiting for messages. To exit press CTRL+C");QueueingConsumer consumer = new QueueingConsumer(channel);channel.basicConsume(QUEUE_NAME, true, consumer);while (true) {QueueingConsumer.Delivery delivery = consumer.nextDelivery();String message = new String(delivery.getBody());System.out.println(" [x] Received '" + message + "'");}}}