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第一个DUBBO例子

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最近dubbo项目重新维护，让人忍不住想了解一下。

本文参考dubbo官方实例实现了一个简单的demo。使用Spring配置文件，zookeeper作为注册器。

1. 项目结构

  • hello-dubbo-api: 公共api接口，provider暴露此接口，consumer调用此接口
  • hello-dubbo-provider: 实现api中的接口，对外提供服务
  • hello-dubbo-consumer: 调用api中的接口

2.父pom依赖管理

首先在父pom中引入dependencyManagement和公共依赖：

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.damon4u.demo</groupId>
    <artifactId>hello-dubbo</artifactId>
    <packaging>pom</packaging>
    <version>1.0-SNAPSHOT</version>
    <modules>
        <module>hello-dubbo-api</module>
        <module>hello-dubbo-provider</module>
        <module>hello-dubbo-consumer</module>
    </modules>
    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java-version>1.7</java-version>
        <junit.version>4.12</junit.version>
        <spring.version>4.3.9.RELEASE</spring.version>
        <org.slf4j.version>1.7.5</org.slf4j.version>
        <logback.version>1.0.13</logback.version>
    </properties>
    <dependencyManagement>
        <dependencies>
            <!-- spring start -->
            <dependency>
                <groupId>org.springframework</groupId>
                <artifactId>spring-framework-bom</artifactId>
                <version>${spring.version}</version>
                <type>pom</type>
                <!-- 注意：import scope只能用在dependencyManagement里面 -->
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.aspectj</groupId>
                <artifactId>aspectjweaver</artifactId>
                <version>1.6.9</version>
            </dependency>
            <dependency>
                <groupId>cglib</groupId>
                <artifactId>cglib</artifactId>
                <version>2.2.2</version>
            </dependency>
            <!-- spring end -->
            <!-- log start -->
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
                <version>${org.slf4j.version}</version>
            </dependency>
            <dependency>
                <groupId>ch.qos.logback</groupId>
                <artifactId>logback-classic</artifactId>
                <version>${logback.version}</version>
            </dependency>
            <dependency>
                <groupId>ch.qos.logback</groupId>
                <artifactId>logback-core</artifactId>
                <version>${logback.version}</version>
            </dependency>
            <dependency>
                <groupId>org.slf4j</groupId>
                <artifactId>jcl-over-slf4j</artifactId>
                <version>${org.slf4j.version}</version>
                <scope>runtime</scope>
            </dependency>
            <!-- log end -->
            <!-- test start -->
            <dependency>
                <groupId>junit</groupId>
                <artifactId>junit</artifactId>
                <version>${junit.version}</version>
                <scope>test</scope>
            </dependency>
            <!-- test end -->
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <!-- log start -->
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-api</artifactId>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
        </dependency>
        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
        </dependency>
        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>jcl-over-slf4j</artifactId>
            <scope>runtime</scope>
        </dependency>
        <!-- log end -->
        <!-- test start -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <scope>test</scope>
        </dependency>
        <!-- test end -->
    </dependencies>
    <build>
        <finalName>hello-dubbo</finalName>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.7</source>
                    <target>1.7</target>
                    <encoding>UTF-8</encoding>
                    <debug>true</debug>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.4.2</version>
                <configuration>
                    <skipTests>true</skipTests>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

3. dubbo-api

新建子模块，作为api，不需要特别的pom依赖引入，只是定义一个简单的接口：

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public interface DemoService {
    /**
     * sayHello
     */
    String sayHello(String name);
}

4. dubbo-provider

新建子模块，作为服务提供者。
首先引入api，dubbo和zookeeper依赖，注意解决日志冲突：

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<dependencies>
    <!-- api start -->
    <dependency>
        <groupId>com.damon4u.demo</groupId>
        <artifactId>hello-dubbo-api</artifactId>
        <version>1.0-SNAPSHOT</version>
    </dependency>
    <!-- api end -->
    <!-- dubbo start -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>dubbo</artifactId>
        <version>2.5.8</version>
    </dependency>
    <dependency>
        <groupId>org.apache.zookeeper</groupId>
        <artifactId>zookeeper</artifactId>
        <version>3.4.9</version>
        <exclusions>
            <exclusion>
                <artifactId>slf4j-log4j12</artifactId>
                <groupId>org.slf4j</groupId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>com.101tec</groupId>
        <artifactId>zkclient</artifactId>
        <version>0.2</version>
    </dependency>
    <!-- dubbo end -->
</dependencies>

其中dubbo的依赖中包含了相关的Spring依赖，如果项目本身使用Spring容器，推荐单独指定Spring依赖。

provider需要实现api接口，对外提供服务：

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public class DemoServiceImpl implements DemoService {
    private static final Logger logger = LoggerFactory.getLogger(DemoServiceImpl.class);
    @Override
    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();
    }
}

接下来是dubbo相关的Spring配置文件：

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<?xml version="1.0" encoding="UTF-8"?>
<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="hello-dubbo-provider"/>
    <!-- 使用zookeeper注册中心暴露发现服务地址 -->
    <dubbo:registry address="zookeeper://10.235.132.202:2181"/>
    <!-- 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.damon4u.demo.dubbo.provider.DemoServiceImpl"/>
    <!-- 声明需要暴露的服务接口 -->
    <dubbo:service interface="com.damon4u.demo.dubbo.api.DemoService" ref="demoService"/>
</beans>

dubbo默认使用log4j作为日志输出，此处我们想使用slf4j代替，需要在dubbo.properties中指定日志类型：

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dubbo.application.logger=slf4j

然后添加logback.xml：

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<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <appender name="Console" class="ch.qos.logback.core.ConsoleAppender">
        <Target>System.out</Target>
        <encoder>
            <pattern>%date [%level] [%thread] %logger{80} [%file : %line] %msg%n</pattern>
        </encoder>
    </appender>
    <logger name="org.springframework" level="info"/>
    <logger name="jdbc.connection" level="OFF"/>
    <logger name="org.apache" level="error"/>
    <logger name="jdbc.resultset" level="OFF"/>
    <logger name="org.apache.ibatis" level="info"/>
    <logger name="jdbc.audit" level="OFF"/>
    <logger name="jdbc.sqlonly" level="INFO"/>
    <logger name="jdbc.sqltiming" level="DEBUG"/>
    <logger name="org.quartz.simpl" level="error"/>
    <logger name="com.alibaba.dubbo" level="INFO"/>
    <root level="debug">
        <appender-ref ref="Console"/>
    </root>
</configuration>

最后是一个启动类：

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public class Provider {
    private static final Logger logger = LoggerFactory.getLogger(Provider.class);
    public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                new String[] {"dubbo-provider.xml"});
        context.start();
        logger.info("Provider Running...");
        System.in.read(); // press any key to exit
    }
}

5. dubbo-consumer

新建子模块，作为api接口调用者。同样导入dubbo-provider中的pom依赖，dubbo.properties和logback.xml。
然后是dubbo相关的Spring配置文件：

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<?xml version="1.0" encoding="UTF-8"?>
<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="hello-dubbo-consumer"/>
    <!-- 使用zookeeper注册中心暴露发现服务地址 -->
    <dubbo:registry address="zookeeper://10.235.132.202:2181"/>
    <!-- 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.damon4u.demo.dubbo.api.DemoService"/>
</beans>

最后是启动类，像使用本地service服务一样，调用api接口：

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public class Consumer {
    private static final Logger logger = LoggerFactory.getLogger(Consumer.class);
    public static void main(String args[]) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[]{"dubbo-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();
            }
        }
    }
}

6. 测试

我们首先启动一台provider和一台consumer，可以看到两者正常调用。

这时，我们更换provider的端口到20881再启动一台provider，可以看到，consumer收到一个notify，zookeeper中注册的地址多了，部分请求被分发到新的节点。

然后我们再启动两台consumer，模拟多个调用者，可以看到请求被分发到两个provider上。

负载均衡的策略还没有研究。

本项目使用zookeeper作为注册中心，此时zookeeper注册节点情况如下（图中使用的工具是ZooInspector.jar）：

当增删节点时，都会有notify通知，提供服务发现。

完整的项目代码在github上：hello-dubbo