dubbo是一个分布式的服务架构，可直接用于生产环境作为SOA服务框架。
官网首页：http://dubbo.io/ ，官方用户指南 http://dubbo.io/User+Guide-zh.htm上面的几张图画得不错，完全可以当做SOA架构的学习资料
淘宝将这个项目开源出来以后，得到了不少同行的支持，包括：
当当网的扩展版本dubbox ：https://github.com/dangdangdotcom/dubbox
京东的扩展版本jd-hydra: http://www.oschina.net/p/jd-hydra
不过，略有遗憾的是，据说在淘宝内部，dubbo由于跟淘宝另一个类似的框架HSF（非开源）有竞争关系，导致dubbo团队已经解散（参见http://www.oschina.net/news/55059/druid-1-0-9 中的评论），反到是当当网的扩展版本仍在持续发展，墙内开花墙外香。
不管如何，能在阿里、当当、京东这些大型网站正式使用的框架，总不至于差到哪里去。
本文下面的示例均基于当当的dubbox版本，由于dubbox并没向maven提交编译后的jar包，所以只能从github clone代码到本地编译得到jar包。
编译及测试步骤：(以下步骤全在windows环境中完成)
1. 本机先安装github on Windows的客户端，将在path路径中，把git.exe加进去
2. 命令行下 git clone https://github.com/dangdangdotcom/dubbox 把代码拉到本地
3. mvn install -Dmaven.test.skip=true 跳过测试编译
4. 在本机安装一个zookeeper，参考zoo.cfg如下：
tickTime=2000
initLimit=10
syncLimit=5
dataDir=D:/java/zookeeper-3.4.6/data
dataLogDir=D:/java/zookeeper-3.4.6/log
clientPort=2181
server.1=localhost:2287:3387
然后输入 bin/zkServer.cmd 启用zookeeper
5. intellij Idea中导入源码
6. 运行 dubboxdubbo-demodubbo-demo-providersrc estjavacomalibabadubbodemoproviderDemoProvider.java
把服务提供方跑起来，成功后，可以在ZK里，用 ls / 看下，会发现zk里多出了一个dubbo的节点，所有服务全注册在这里了
7. 运行dubboxdubbo-demodubbo-demo-consumersrc estjavacomalibabadubbodemoconsumerDemoConsumer.java
服务消费方调用测试，可以看console里的输出
8. 运行dubboxdubbo-demodubbo-demo-consumersrc estjavacomalibabadubbodemoconsumerRestClient.java
跑一下rest调用
9. 浏览器访问 http://localhost:8888/services/users/100.xml 或 http://localhost:8888/services/users/100.json
dubbox官方的示例，虽然已经很简单了，但是对于初次接触的人来讲，仍然略显复杂，下面的代码在其基础上简化了一下：
一、先定义服务接口及传输对象DTO
项目结构如下
代码：
User.java
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package yjmyzz.dubbo.demo.api;import org.codehaus.jackson.annotate.JsonProperty;import javax.validation.constraints.Min;import javax.validation.constraints.NotNull;import javax.validation.constraints.Size;import javax.xml.bind.annotation.XmlAccessType;import javax.xml.bind.annotation.XmlAccessorType;import javax.xml.bind.annotation.XmlElement;import javax.xml.bind.annotation.XmlRootElement;import java.io.Serializable;@XmlRootElement@XmlAccessorType(XmlAccessType.FIELD)public class User implements Serializable { @NotNull @Min(1L) private Long id; @JsonProperty("username") @XmlElement(name = "username") @NotNull @Size(min = 6, max = 50) private String name; public User() { } public User(Long id, String name) { this.id = id; this.name = name; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } @Override public String toString() { return "User (" + "id=" + id + ", name='" + name + ''' + ')'; }} |
UserService.java
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package yjmyzz.dubbo.demo.api;public interface UserService { User getUser(Long id);} |
UserRestService.java
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package yjmyzz.dubbo.demo.api;import javax.validation.constraints.Min;public interface UserRestService { User getUser(@Min(value = 1L, message = "User ID must be greater than 1") Long id);} |
pom.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <project xmlns="http://maven.apache.org/POM/4.0.0" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> 5 6 <modelVersion>4.0.0</modelVersion> 7 8 <groupId>com.cnblogs.yjmyzz</groupId> 9 <artifactId>dubbo-hello-api</artifactId> 10 <version>0.1</version> 11 12 <dependencies> 13 14 <dependency> 15 <groupId>com.alibaba</groupId> 16 <artifactId>dubbo</artifactId> 17 <version>2.8.4</version> 18 </dependency> 19 20 <dependency> 21 <groupId>javax.validation</groupId> 22 <artifactId>validation-api</artifactId> 23 <version>1.0.0.GA</version> 24 </dependency> 25 26 <dependency> 27 <groupId>javax.annotation</groupId> 28 <artifactId>javax.annotation-api</artifactId> 29 <version>1.2</version> 30 </dependency> 31 32 <dependency> 33 <groupId>org.codehaus.jackson</groupId> 34 <artifactId>jackson-mapper-asl</artifactId> 35 <version>1.9.12</version> 36 </dependency> 37 38 </dependencies> 39 </project>
二、定义服务生产者（即：服务接口的实现方）
UserServiceImpl.java
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package yjmyzz.dubbo.demo.provider;import yjmyzz.dubbo.demo.api.User;import yjmyzz.dubbo.demo.api.UserService;public class UserServiceImpl implements UserService { public User getUser(Long id) { return new User(id, "username" + id); }} |
UserRestServiceImpl.java
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package yjmyzz.dubbo.demo.provider;import com.alibaba.dubbo.rpc.RpcContext;import com.alibaba.dubbo.rpc.protocol.rest.support.ContentType;import yjmyzz.dubbo.demo.api.User;import yjmyzz.dubbo.demo.api.UserRestService;import yjmyzz.dubbo.demo.api.UserService;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.ws.rs.*;import javax.ws.rs.core.MediaType;@Path("users")@Consumes({MediaType.APPLICATION_JSON, MediaType.TEXT_XML})@Produces({ContentType.APPLICATION_JSON_UTF_8, ContentType.TEXT_XML_UTF_8})public class UserRestServiceImpl implements UserRestService { private UserService userService; public void setUserService(UserService userService) { this.userService = userService; } @GET @Path("{id : \d+}") public User getUser(@PathParam("id") Long id) { if (RpcContext.getContext().getRequest(HttpServletRequest.class) != null) { System.out.println("Client IP address from RpcContext: " + RpcContext.getContext().getRequest(HttpServletRequest.class).getRemoteAddr()); } if (RpcContext.getContext().getResponse(HttpServletResponse.class) != null) { System.out.println("Response object from RpcContext: " + RpcContext.getContext().getResponse(HttpServletResponse.class)); } return userService.getUser(id); }} |
DemoProvider.java
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package yjmyzz.dubbo.demo.provider;import org.springframework.context.support.ClassPathXmlApplicationContext;import java.io.IOException;public class DemoProvider { public static void main(String[] args) throws IOException { ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath*:META-INF/spring/*.xml"); context.start(); System.out.println("服务已经启动..."); System.in.read(); }} |
配置文件：resourcesMETA-INFspringdubbo-demo-provider.xml
pom.xml
测试时，运行DemoProvider中的main方法即可启动服务，所有服务注册在ZooKeeper，层次结构类似下面这样：
/dubbo
/dubbo/yjmyzz.dubbo.demo.api.UserRestService
/dubbo/yjmyzz.dubbo.demo.api.UserRestService/providers
/dubbo/yjmyzz.dubbo.demo.api.UserRestService/configurators
/dubbo/yjmyzz.dubbo.demo.api.UserService
/dubbo/yjmyzz.dubbo.demo.api.UserService/providers
/dubbo/yjmyzz.dubbo.demo.api.UserService/configurators
三、服务消费方
DemoConsumer.java
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package yjmyzz.dubbo.demo.consumer;import org.springframework.context.support.ClassPathXmlApplicationContext;import yjmyzz.dubbo.demo.api.UserService;import javax.ws.rs.client.Client;import javax.ws.rs.client.ClientBuilder;import javax.ws.rs.client.WebTarget;import javax.ws.rs.core.Response;public class DemoConsumer { public static void main(String[] args) { final String port = "8888"; //测试Rest服务 getUser("http://localhost:" + port + "/services/users/1.json"); getUser("http://localhost:" + port + "/services/users/1.xml"); //测试常规服务 ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath*:META-INF/spring/*.xml"); context.start(); UserService userService = context.getBean(UserService.class); System.out.println(userService.getUser(1L)); } private static void getUser(String url) { System.out.println("Getting user via " + url); Client client = ClientBuilder.newClient(); WebTarget target = client.target(url); Response response = target.request().get(); try { if (response.getStatus() != 200) { throw new RuntimeException("Failed with HTTP error code : " + response.getStatus()); } System.out.println("Successfully got result: " + response.readEntity(String.class)); } finally { response.close(); client.close(); } }} |
配置文件：resourcesMETA-INFspringdubbo-hello-consumer.xml
1 <?xml version="1.0" encoding="UTF-8"?> 2 <beans xmlns="http://www.springframework.org/schema/beans" 3 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 4 xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" 5 xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd 6 http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> 7 8 <dubbo:application name="demo-consumer" owner="programmer" organization="dubbox"/> 9 10 <dubbo:registry address="zookeeper://127.0.0.1:2181"/> 11 12 <dubbo:reference id="userRestService" interface="yjmyzz.dubbo.demo.api.UserRestService"/> 13 14 <dubbo:reference id="userService" interface="yjmyzz.dubbo.demo.api.UserService"/> 15 16 </beans>
pom.xml
其它注意事项：
dubbo构架中，zk充着“服务注册中心”的角色，所以生产者与消费者的xml配置文件中，都要配置zk地址，如果zk采用集群部署时，配置写法参考下面这样：
<dubbo:registry address="zookeeper://172.28.*.102:2181?backup=172.28.*.102:2182,172.28.*.102:2183"/>
dubbo还有一个管理界面，用于服务治理，包括启用/禁用服务，设置服务的路由规则（即：A地址的Consumer直接调用B机器的Provider，而不是由负载均衡算法分配）等等。
使用方法：将dubbo-admin这个项目编译成war包后，部署到jetty或其它兼容web server即可（当然要修改WEB-INFdubbo.properties里zk的地址）
部署完成后，访问管理界面时，默认用户名，密码均是root。
另外dubbo-monitor项目用于性能监控，结合监控产生的数据，再套上一些图表展示的框架，可以用图表方式直观展示各种指标。
注：官网给出的dubbo-admin采用的webx架构有点老，而且除了淘宝之外，几乎没人在用，dubbo-monitor-simple界面也比较古朴，所以社区也人对其做了扩展，详情参考另一篇博客dubbox 的各种管理和监管
2016-02-25：dubbox依赖的spring虽然升级成3.x了，但版本还是有点低，spring都已经4.x了，为了方便我fork了一份，升级成spring 4.x 同时增加了log4j2的日志组件支持，详情见：dubbox升级spring到4.x及添加log4j2支持
参考文章：
http://shiyanjun.cn/archives/341.html
http://blog.csdn.net/wilsonke/article/details/39896595
http://www.dataguru.cn/thread-464197-1-1.html
http://www.iteye.com/magazines/103
http://dangdangdotcom.github.io/dubbox/rest.html