参考文档：
官方文档：http://dubbo.io/
duboo中文：https://dubbo.gitbooks.io/dubbo-user-book/content/preface/background.html
1、是什么：
Dubbo |ˈdʌbəʊ| is a high-performance, java based RPC framework open-sourced by Alibaba. As in many RPC systems, dubbo is based around the idea of defining a service, specifying the methods that can be called remotely with their parameters and return types. On the server side, the server implements this interface and runs a dubbo server to handle client calls. On the client side, the client has a stub that provides the same methods as the server.
大体意思：Dubbo是阿里巴巴公司开源的一个高性能优秀的服务框架，使得应用可通过高性能的 RPC 实现服务的输出和输入功能，特点是：可以和Spring框架无缝集成。。。。
首先说说ZK是做什么的：
ZooKeeper是一个分布式的，开放源码的分布式应用程序协调服务，是Google的Chubby一个开源的实现，是Hadoop和Hbase的重要组件。它是一个为分布式应用提供一致性服务的软件，提供的功能包括：配置维护、域名服务、分布式同步、组服务等。
在dubbo中，dubbo的服务提供者会在zookeeper上面创建一个临时节点，表明自己的ip和端口，当消费者需要使用服务时，会先在zookeeper上面查询，找到服务提供者，做一些负载的选择（比如随机、轮流），然后按照这些信息，访问服务提供者。
ZK的安装：https://blog.csdn.net/the_fool_/article/details/80774500
2、官方文档中的解释：
场景1、当服务越来越多时，服务 URL 配置管理变得非常困难，F5 硬件负载均衡器的单点压力也越来越大。
此时需要一个服务注册中心，动态的注册和发现服务，使服务的位置透明。并通过在消费方获取服务提供方地址列表，实现软负载均衡和 Failover，降低对 F5 硬件负载均衡器的依赖，也能减少部分成本。
场景2、当进一步发展，服务间依赖关系变得错踪复杂，甚至分不清哪个应用要在哪个应用之前启动，架构师都不能完整的描述应用的架构关系.
这时 需要自动画出应用间的依赖关系图，以帮助架构师理清理关系。
场景3、接着，服务的调用量越来越大，服务的容量问题就暴露出来，这个服务需要多少机器支撑？什么时候该加机器？
为了解决这些问题，第一步，要将服务现在每天的调用量，响应时间，都统计出来，作为容量规划的参考指标。其次，要可以动态调整权重，在线上，将某台机器的权重一直加大，并在加大的过程中记录响应时间的变化，直到响应时间到达阀值，记录此时的访问量，再以此访问量乘以机器数反推总容量 。
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3、架构（这个图刚看时不是很理解，但是结合组件来看还是很清晰的）：
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4、官方demo：
1、项目结构：
2、导包（pom.xml）：
<!--
- Copyright 1999-2011 Alibaba Group.
-
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
-
- http://www.apache.org/licenses/LICENSE-2.0
-
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License.
-->
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>com.alibaba</groupId>
<artifactId>dubbo-demo</artifactId>
<version>2.5.8</version>
</parent>
<artifactId>dubbo-demo-provider</artifactId>
<packaging>jar</packaging>
<name>${project.artifactId}</name>
<description>The demo provider module of dubbo project</description>
<properties>
<skip_maven_deploy>false</skip_maven_deploy>
</properties>
<dependencies>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>dubbo-demo-api</artifactId>
<version>${project.parent.version}</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>dubbo</artifactId>
<version>${project.parent.version}</version>
</dependency>
<dependency>
<groupId>com.101tec</groupId>
<artifactId>zkclient</artifactId>
</dependency>
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-framework</artifactId>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
</dependency>
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.4</version>
</dependency>
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.0.35.Final</version>
</dependency>
</dependencies>
</project>3、生产者：
public class DemoServiceImpl implements DemoService {
public String sayHello(String name) {
System.out.println("[" + new SimpleDateFormat("HH:mm:ss").format(new Date()) + "] Hello " + name + ", request from consumer: " + RpcContext.getContext().getRemoteAddress());
return "Hello " + name + ", response form provider: " + RpcContext.getContext().getLocalAddress();
}
}提供服务：
public class Provider {
public static void main(String[] args) throws Exception {
//Prevent to get IPV6 address,this way only work in debug mode
//But you can pass use -Djava.net.preferIPv4Stack=true,then it work well whether in debug mode or not
System.setProperty("java.net.preferIPv4Stack", "true");
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"META-INF/spring/dubbo-demo-provider.xml"});
context.start();
System.in.read(); // press any key to exit
}
}配置文件dubbo-demo-provider.xml：
<?xml version="1.0" encoding="UTF-8"?>
<!--
- Copyright 1999-2011 Alibaba Group.
-
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
-
- http://www.apache.org/licenses/LICENSE-2.0
-
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License.
-->
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">
<!-- 提供方应用信息，用于计算依赖关系 -->
<dubbo:application name="demo-provider"/>
<!-- 使用multicast广播注册中心暴露服务地址 -->
<!--<dubbo:registry address="multicast://224.5.6.7:1234"/>-->
<!-- 这是我自己的注册中心，安装启动即可，dubbo会自动创建节点。-->
<dubbo:registry address="zookeeper://192.168.0.17:2181" />
<!-- 用dubbo协议在20880端口暴露服务 -->
<dubbo:protocol name="dubbo" port="20880"/>
<!-- 和本地bean一样实现服务 -->
<bean id="demoService" class="com.alibaba.dubbo.demo.provider.DemoServiceImpl"/>
<!-- 声明需要暴露的服务接口 -->
<dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/>
</beans>4、消费者：
public class Consumer {
public static void main(String[] args) {
//Prevent to get IPV6 address,this way only work in debug mode
//But you can pass use -Djava.net.preferIPv4Stack=true,then it work well whether in debug mode or not
System.setProperty("java.net.preferIPv4Stack", "true");
ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"META-INF/spring/dubbo-demo-consumer.xml"});
context.start();
DemoService demoService = (DemoService) context.getBean("demoService"); // get remote service proxy
while (true) {
try {
Thread.sleep(1000);
String hello = demoService.sayHello("world"); // call remote method
System.out.println(hello); // get result
} catch (Throwable throwable) {
throwable.printStackTrace();
}
}
}
}配置文件dubbo-demo-consumer.xml：
<?xml version="1.0" encoding="UTF-8"?>
<!--
- Copyright 1999-2011 Alibaba Group.
-
- Licensed under the Apache License, Version 2.0 (the "License");
- you may not use this file except in compliance with the License.
- You may obtain a copy of the License at
-
- http://www.apache.org/licenses/LICENSE-2.0
-
- Unless required by applicable law or agreed to in writing, software
- distributed under the License is distributed on an "AS IS" BASIS,
- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- See the License for the specific language governing permissions and
- limitations under the License.
-->
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
xmlns="http://www.springframework.org/schema/beans"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd">
<!-- 消费方应用名，用于计算依赖关系，不是匹配条件，不要与提供方一样 -->
<dubbo:application name="demo-consumer"/>
<!-- 使用multicast广播注册中心暴露发现服务地址 -->
<!--<dubbo:registry address="multicast://224.5.6.7:1234"/>-->
<!-- 去我自己安装的注册中心索取服务 -->
<dubbo:registry address="zookeeper://192.168.0.17:2181" />
<!-- 生成远程服务代理，可以和本地bean一样使用demoService -->
<dubbo:reference id="demoService" check="false" interface="com.alibaba.dubbo.demo.DemoService"/>
</beans>与cloud的区别？如何选择？
个人观点：博主了解的并不深入，个人觉得springcloud更加全面，使用起来更顺手一点。等熟练用过后会考虑做个对比。