NATS学习 -- 实践之发布订阅（Publish Subscribe）续

野性酷女 2022-07-30 13:55 141阅读 0赞

上一篇博客介绍了基于java的NATS的发布订阅模式。

今天发现其实服务器我们可以不用启动，因为nats为我们提供了一个服务器，可以用来测试。

demo.nats.io

好的，我们直接进入今天的主题。

今天采用一个 simple Java client for NATS

参考地址

[NATS学习 – 概念学习之消息（Message）与发布订阅（Publish Subscribe）][NATS_ _ _Message_Publish Subscribe]

使用很简单

# 依赖的jar包 #

<dependency>
        <groupId>com.github.cloudfoundry-community</groupId>
        <artifactId>nats-client</artifactId>
        <version>0.6.4</version>
    </dependency>
    
    <dependency>
        <groupId>io.netty</groupId>
        <artifactId>netty-all</artifactId>
        <version>5.0.0.Alpha2</version>
    </dependency>
    
    <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-annotations</artifactId>
       <version>2.4.0</version>
    </dependency>
    <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-databind</artifactId>
       <version>2.4.0</version>
    </dependency>
    <dependency>
       <groupId>com.fasterxml.jackson.core</groupId>
       <artifactId>jackson-core</artifactId>
       <version>2.4.0</version>
    </dependency>
    
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.7.21</version>
    </dependency>
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-log4j12</artifactId>
        <version>1.7.21</version>
    </dependency>
    <dependency>
        <groupId>log4j</groupId>
        <artifactId>log4j</artifactId>
        <version>1.2.17</version>
    </dependency>

# Publish.java #

import java.util.Scanner;
    
    import nats.client.Nats;
    import nats.client.NatsConnector;
    
    public class Publish { 
        public static void main(String[] args) {
            Nats nats = new NatsConnector().addHost("nats://demo.nats.io:4222").connect();
    
            @SuppressWarnings("resource")
            Scanner scanner = new Scanner(System.in);
            System.out.println("请输入字符串：");
    
            while (true) {
                String line = scanner.nextLine();
                // 发布消息
                nats.publish("hello", line);
            }
    
        }
    
    }

# Subscribe.java #

package com.gwc.mavenlearn.jnats;
    
    import java.util.concurrent.TimeUnit;
    
    import nats.client.Message;
    import nats.client.MessageHandler;
    import nats.client.MessageIterator;
    import nats.client.Nats;
    import nats.client.NatsConnector;
    import nats.client.Subscription;
    
    public class Subscribe { 
        public static void main(String[] args) {
            Nats nats = new NatsConnector().addHost("nats://demo.nats.io:4222").connect();
    
            Subscription subscription = nats.subscribe("hello");
    
            // 多个消息处理器
    
            // Multiple message handlers
            subscription.addMessageHandler(new MessageHandler() {
                public void onMessage(Message message) {
                    System.out.println("Handler 1");
                    System.out.println(message.getBody());
                }
            });
            subscription.addMessageHandler(new MessageHandler() {
                public void onMessage(Message message) {
                    System.out.println("Handler 2");
                    System.out.println(message.getBody());
                }
            });
    
            // 下面的程序主要是为了不让程序退出，不退出才能收到消息
            // 可以有如下三种方式不让程序退出
            // Block until a message arrives (message handlers still get called)
            MessageIterator iterator = subscription.iterator();
            Message message = iterator.next();
    
            // Or we can block for a limited amount of time
            // message = iterator.next(1, TimeUnit.MINUTES);
    
            // Or we can just use a for loop
            /*for (Message message1 : subscription) { System.out.println(message1); }*/
    
        }
    
    }

# 实验 #

就绪的Subscribe  
![这里写图片描述][20160418190454544]

就绪的Publish  
![这里写图片描述][20160418190544907]

发消息和收消息  
发消息  
![这里写图片描述][20160418190721155]  
收消息  
![这里写图片描述][20160418190647248]

关于日志的配置，参考上一篇博客

[NATS学习 – 概念学习之消息（Message）与发布订阅（Publish Subscribe）][NATS_ _ _Message_Publish Subscribe]

# 参考文献 #

> [simple Java client for NATS ][simple Java client for NATS]
> 
> [NATS API Documentation][]

[NATS_ _ _Message_Publish Subscribe]: http://blog.csdn.net/frankcheng5143/article/details/51161206
[20160418190454544]: /images/20220724/cc74f1fae284468ca2d54f4bdacff1a4.png
[20160418190544907]: /images/20220724/47fdec02e00c4fe5a1125fcf57a0c67b.png
[20160418190721155]: /images/20220724/2c22282eb4774ee2adf0cc431e1d4522.png
[20160418190647248]: /images/20220724/d8c394ec876c4bd68a617c236a07b541.png
[simple Java client for NATS]: https://github.com/cloudfoundry-community/java-nats/tree/master/client
[NATS API Documentation]: http://cloudfoundry-community.github.io/java-nats/apidocs/0.5.1/client/index.html