该模块核心的类为Consumer，主要是一个main函数
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(); } } } }其主要功能是加载配置文件，用于寻找服务提供方所在的位置，拿到DemoService接口的实现类DemoServiceImpl，并调用其方法实现sayHello
dubbo-demo-provider
该模块包含了DemoService的实现类DemoServiceImpl，同时包含一个服务启动类Provider
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 } }启动注册中心
因为调用方和服务提供方需要靠注册中心来联系，提供方将自己的服务登记到注册中心，调用方需要拉取可用的服务提供方的位置信息，比较常见的关系描述如下图所示
调用关系说明
服务容器负责启动，加载，运行服务提供者。
服务提供者在启动时，向注册中心注册自己提供的服务。
服务消费者在启动时，向注册中心订阅自己所需的服务。
注册中心返回服务提供者地址列表给消费者，如果有变更，注册中心将基于长连接推送变更数据给消费者。
服务消费者，从提供者地址列表中，基于软负载均衡算法，选一台提供者进行调用，如果调用失败，再选另一台调用。
服务消费者和提供者，在内存中累计调用次数和调用时间，定时每分钟发送一次统计数据到监控中心。
鉴于Dubbo源码中，配置文件中的默认配置是multicast，但是我在运行的时候总是出现can't assign address的情况，所以改用zookeeper。
相应修改如下，在dubbo-demo-provider项目中，将dubbo-demo-provider.xml修改为
<?xml version="1.0" encoding="UTF-8"?> <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You 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 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://code.alibabatech.com/schema/dubbo/dubbo.xsd"> <!-- provider's application name, used for tracing dependency relationship --> <dubbo:application/> <!-- use multicast registry center to export service --> <dubbo:registry address="zookeeper://127.0.0.1:2181"/> <!-- use dubbo protocol to export service on port 20880 --> <dubbo:protocol port="20880"/> <!-- service implementation, as same as regular local bean --> <bean/> <!-- declare the service interface to be exported --> <dubbo:service interface="com.alibaba.dubbo.demo.DemoService" ref="demoService"/> </beans>将dubbo-demo-consumer项目中的dubbo-demo-consumer.xml修改为
<?xml version="1.0" encoding="UTF-8"?> <!-- Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You 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 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://code.alibabatech.com/schema/dubbo/dubbo.xsd"> <!-- consumer's application name, used for tracing dependency relationship (not a matching criterion), don't set it same as provider --> <dubbo:application/> <!-- use multicast registry center to discover service --> <dubbo:registry address="zookeeper://127.0.0.1:2181"/> <!-- generate proxy for the remote service, then demoService can be used in the same way as the local regular interface --> <dubbo:reference check="false" interface="com.alibaba.dubbo.demo.DemoService"/> </beans>同时在命令行输入zkServer start启动zk
分别启动Proiver和Consumer
运行Provider类，将自己的服务接口对外开放