1 "Hello World!"

Introduction（简介）

RabbitMQ is a message broker: it accepts and forwards messages. You can think about it as a post office: when you put the mail that you want posting in a post box, you can be sure that Mr. Postman will eventually deliver the mail to your recipient. In this analogy, RabbitMQ is a post box, a post office and a postman.

RabbitMQ是一个消息代理：它接受并转发消息。你可以将它看成是一个邮局：当你将想发送的邮件丢进邮箱时，你就可以确定邮差最终会把这封邮件送到收件人手上。通过这个类比来看，RabbitMQ既是邮箱，又是邮局，而且还是邮差。

The major difference between RabbitMQ and the post office is that it doesn't deal with paper, instead it accepts, stores and forwards binary blobs of data ‒ messages.

RabbitMQ和邮局之间的主要不同点是，RabbitMQ不跟纸打交道，它只接收，存储并转发二进制的数据包—消息。

RabbitMQ, and messaging in general, uses some jargon.

RabbitMQ，一般称它为消息队列，它使用了一些术语。

Producing means nothing more than sending. A program that sends messages is a producer:

消息生产其实就是消息发送。发送消息的程序就是生产者：

image

A queue is the name for a post box which lives inside RabbitMQ. Although messages flow through RabbitMQ and your applications, they can only be stored inside a queue. A queue is only bound by the host's memory & disk limits, it's essentially a large message buffer. Many producers can send messages that go to one queue, and many consumers can try to receive data from one queue. This is how we represent a queue:

队列就是相当于RabbitMQ内部的邮箱。虽然消息在传递时是流经RabbitMQ和你的应用，但它们只能被存储在某个队列里。队列大小只受限于主机内存和硬盘容量，它本质上就是个大的消息缓存。多个生产者可以往一个队列里发送消息，多个消费者可以从一个队列里获取数据。以下是我们表示一个队列的方式：

image

Consuming has a similar meaning to receiving. A consumer is a program that mostly waits to receive messages:

消息消费其实就是消息接收。等待接收消息的程序就是一个消费者：

image

Note that the producer, consumer, and broker do not have to reside on the same host; indeed in most applications they don't.

注意，生产者，消费者和代理不一定都在同一个主机里；实际上，在大多数应用中，这三者都不是在同一个主机里。

"Hello World"

In this part of the tutorial we'll write two programs using the spring-amqp library; a producer that sends a single message, and a consumer that receives messages and prints them out. We'll gloss over some of the detail in the Spring-amqp API, concentrating on this very simple thing just to get started. It's a "Hello World" of messaging.

在本教程里，我们将写两个基于spring-amqp类库的程序，其中一个是发送单条消息的生产者，另一个是消费者，它接收消息并将它们打印出来。我们将省略Spring-amqp API的一些细节，专注于即将开始的东西。它是消息队列版本的“Hello World”程序。

In the diagram below, "P" is our producer and "C" is our consumer. The box in the middle is a queue - a message buffer that RabbitMQ keeps on behalf of the consumer.

在下面的图中，“P”是我们的生产者，“C”是我们的消费者。图中间的箱子是一个队列，也就是RabbitMQ给消费者用的的消息缓存：

image

The Spring AMQP Framework（Spring AMQP框架）

RabbitMQ speaks multiple protocols. This tutorial uses AMQP 0-9-1, which is an open, general-purpose protocol for messaging. There are a number of clients for RabbitMQ in many different languages.

RabbitMQ支持多种协议。本教程使用AMQP 0-9-1协议，它是一个开放，通用的消息队列协议。很多编程语言都提供了RabbitMQ客户端。

Spring AMQP leverages Spring Boot for configuration and dependency management. Spring supports maven or gradle but for this tutorial we'll select maven with Spring Boot 1.5.2. Open the Spring Initializr and provide: the group id (e.g. org.springframework.amqp.tutorials) the artifact id (e.g. rabbitmq-amqp-tutorials). Search for the amqp dependency and select the AMQP dependency.

Spring AMQP利用Spring Boot来进行配置和依赖管理。Spring同时支持maven或者gradle，但在本教程里我们选择用maven，同时采用Spring Boot 1.5.2版本。我们打开Spring Initializr并提供group id（如org.springframework.amqp.tutorials）和artifact id（如rabbitmq-amqp-tutorials）。查找amqp依赖并选择AMQP依赖。（译者注：应该是搜索rabbitmq）

Generate the project and unzip the generated project into the location of your choice. This can now be imported into your favorite IDE. Alternatively you can work on it from your favorite editor.

点击Generate Project生成项目，下载并将其解压到你想存放的目录。现在你可以在你喜欢的IDE里面导入这个项目。你也可以在你喜欢的编辑器上进行下一步编辑。

Configuring the project（配置项目）

Spring Boot offers numerous features but we will only highlight a few here. First, Spring Boot applications have the option of providing their properties through either an application.properties or application.yml file (there are many more options as well but this will get us going). You'll find an application.properties file in the generated project with nothing in it. Rename application.properties to application.yml file with the following properties:

Spring Boot提供了很多特性，但在这里我们只显示几个需要用到的。首先，Spring Boot应用的配置可以写在application.properties文件或者application.yml文件里（还有许多其它的方式，但对于我们，用这两种文件就足够了）。你在生成的项目里将会找到一个空的application.properties文件。将这个文件重命名为application.yml，并写上这些属性：

spring:
    profiles:
        active: usage_message

logging:
    level:
        org: ERROR

tutorial:
    client:
        duration: 10000

Create a new directory (package - tut1) where we can put the tutorial code. We'll now create a JavaConfig file (Tut1Config.java) to describe our beans in the following manner:

创建一个新的目录（package - tut1）用来放我们的教程代码。现在我们将通过以下方式创建一个Java配置文件（Tut1Config.java）来描述我们的Bean：

package org.springframework.amqp.tutorials.tut1;

import org.springframework.amqp.core.Queue;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Profile;

@Profile({"tut1","hello-world"})
@Configuration
public class Tut1Config {

    @Bean
    public Queue hello() {
        return new Queue("hello");
    }

    @Profile("receiver")
    @Bean
    public Tut1Receiver receiver() {
        return new Tut1Receiver();
    }

    @Profile("sender")
    @Bean
    public Tut1Sender sender() {
        return new Tut1Sender();
    }
}

Note that we've defined the 1st tutorial profile as either tut1, the package name, or hello-world. We use the @Configuration to let Spring know that this is a Java Configuration and in it we create the definition for our Queue ("hello") and define our Sender and Receiver beans.

注意，我们已经将教程的第一个配置组定义为tu1（即报名），或者hello-world。我们用@Configuration注解来让Spring知道这是个Java配置，并且在配置里我们定义了队列Queue("hello")，而且也定义了我们的发送者和接收者。

We will run all of our tutorials through the Boot Application now by simply passing in which profiles we are using. To enable this we will modify the generated RabbitAmqpTutorialsApplication.java with the following:

现在我们将传入需要用到配置组，通过Boot Application来运行我们的教程。为了做到这一点，我们将修改生成的RabbitAmqpTutorialsApplication.java文件，如下所示：

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Profile;
import org.springframework.scheduling.annotation.EnableScheduling;

@SpringBootApplication
@EnableScheduling
public class RabbitAmqpTutorialsApplication {

    @Profile("usage_message")
    @Bean
    public CommandLineRunner usage() {
        return new CommandLineRunner() {

            @Override
            public void run(String... arg0) throws Exception {
                System.out.println("This app uses Spring Profiles to control its behavior.\n");
                System.out.println("Sample usage: java -jar rabbit-tutorials.jar --spring.profiles.active=helloworld,sender");
            }
      };
  }

    @Profile("!usage_message")
    @Bean
    public CommandLineRunner tutorial() {
        return new RabbitAmqpTutorialsRunner();
    }

    public static void main(String[] args) throws Exception {
        SpringApplication.run(RabbitAmqpTutorialsApplication.class, args);
    }
}

and add the RabbitAmqpTutorialsRunner.java code as follows:

然后像下面那样添加RabbitAmqpTutorialsRunner.java代码：

package org.springframework.amqp.tutorials;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.CommandLineRunner;
import org.springframework.context.ConfigurableApplicationContext;

public class RabbitAmqpTutorialsRunner implements CommandLineRunner {

    @Value("${tutorial.client.duration:0}")
    private int duration;

    @Autowired
    private ConfigurableApplicationContext ctx;

    @Override
    public void run(String... arg0) throws Exception {
        System.out.println("Ready ... running for " + duration + "ms");
        Thread.sleep(duration);
        ctx.close();
    }
}

Sending（发送）

image

Now there is very little code that needs to go into the sender and receiver classes. Let's call them Tut1Receiver and Tut1Sender. The Sender leverages our config and the RabbitTemplate to send the message.

现在发送者类和接收者类需要写的代码很少。我们把接收者的类名叫做Tut1Receiver，把发送者的类名叫做Tut1Sender。发送者类利用我们的配置和RabbitTemplate类来发送消息。

// Sender
package org.springframework.amqp.tutorials.tut1;

import org.springframework.amqp.core.Queue;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Scheduled;

public class Tut1Sender {

    @Autowired
    private RabbitTemplate template;

    @Autowired
    private Queue queue;

    @Scheduled(fixedDelay = 1000, initialDelay = 500)
    public void send() {
        String message = "Hello World!";
        this.template.convertAndSend(queue.getName(), message);
        System.out.println(" [x] Sent '" + message + "'");
    }
}

You'll notice that spring-amqp removes the boiler plate code leaving you with only the logic of the messaging to be concerned about. We autowire in the queue that was configured in our bean definition in the Tut1Config class and like many spring connection abstractions, we wrap the boilerplate rabbitmq client classes with a RabbitTemplate that can be autowired into the sender. All that is left is to create a message and invoke the template's convertAndSend method passing in the queue name from the bean we defined and the message we just created.

你会发觉，spring-amqp移除了样板化代码，让你只专注于消息发送逻辑。我们自动注入了队列queue，它已经在前面的Tut1Config类里做了配置。就像大多数Spring连接抽象，我们用RabbitTemplate包装了样板化的rabbitmq客户端类，并将它自动注入到发送者类里。我们要做的就是创建一条信息，并调用template的convertAndSend方法，传入我们定义的队列bean的名字以及我们刚创建的信息。

Sending doesn't work!（无法发送！）

If this is your first time using RabbitMQ and you don't see the "Sent" message then you may be left scratching your head wondering what could be wrong. Maybe the broker was started without enough free disk space (by default it needs at least 200 MB free) and is therefore refusing to accept messages. Check the broker logfile to confirm and reduce the limit if necessary. The configuration file documentation will show you how to set disk_free_limit.

如果这是你第一次使用RabbitMQ并且你看不到打印出来的“Sent”消息，你可能会在那里苦恼着哪里出错了。也许消息代理在启动时不够磁盘空间（默认它需要200MB的空间），由此导致拒绝接收信息。如有必要，检查代理的日志文件来确认并减少所需最小磁盘空间的限制。配置文件文档里会告诉你如何设置disk_free_limit（最小所需磁盘空间）参数

Receiving（接收）

The receiver is equally simple. We annotate our Receiver class with @RabbitListener and pass in the name of the queue. We then annotate our receive method with @RabbitHandler passing in the payload that has been pushed to the queue.

接收者类很简单。我们用@RabbitListener来注解我们的接收者类，并往注解里传入队列的名字。然后我们用@RabbitHandler来注解我们的接收方法，接收的参数为推入队列里的负载。

package org.springframework.amqp.tutorials.tut1;

import org.springframework.amqp.rabbit.annotation.RabbitHandler;
import org.springframework.amqp.rabbit.annotation.RabbitListener;

@RabbitListener(queues = "hello")
public class Tut1Receiver {

    @RabbitHandler
    public void receive(String in) {
        System.out.println(" [x] Received '" + in + "'");
    }
}

Putting it all together（代码整合）

The app uses Spring Profiles to control what tutorial it's running, and whether it's a Sender or Receiver. Choose which tutorial to run by using the profile. For example:

程序通过使用Spring配置组来控制正在运行的是哪个教程代码，以及控制正在运行的是发送者还是接收者。我们选择使用不同的配置组来运行不同的教程代码。例如：

- {tut1|hello-world},{sender|receiver}
- {tut2|work-queues},{sender|receiver}
- {tut3|pub-sub|publish-subscribe},{sender|receiver}
- {tut4|routing},{sender|receiver}
- {tut5|topics},{sender|receiver}
- {tut6|rpc},{client|server}

We'll come back to this list as we progress through the other five tutorials. After building with maven, run the app however you like to run boot apps (e.g. from the ide, or command line). We'll show how to run from the command line.

涉及到其它五个教程时我们还会回来参照这个列表。用maven构建完后，你可以用你喜欢的方式来运行程序（例如，通过ide或通过命令行）。我们将展示如何通过命令行来运行。

For example（例如）:

# publisher
java -jar rabbitmq-tutorials.jar --spring.profiles.active=hello-world,sender

# consumer
java -jar rabbitmq-tutorials.jar --spring.profiles.active=hello-world,receiver

Listing queues（列出队列）

You may wish to see what queues RabbitMQ has and how many messages are in them. You can do it (as a privileged user) using the rabbitmqctl tool:

你可能希望看一下RabbitMQ有哪些队列，这些队列里有多少消息。你可以通过使用rabbitmqctl工具来查看（但你必须是个授权用户）：

sudo rabbitmqctl list_queues

On Windows, omit the sudo:

在Windows系统上，输入命令时要去掉sudo：

rabbitmqctl.bat list_queues

Time to move on to part 2 and build a simple work queue.

接下来我们开始教程的第2部份，并构建一个简单的工作队列。

转自我的博客：https://jiapengcai.github.io/posts/53264/