Dubbo实践入门示例
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dubbo是一个分布式服务框架，致力于提供高性能和透明化的RPC远程服务调用方案，以及SOA服务治理方案。简单的说，dubbo就是个服务框架，如果没有分布式的需求，其实是不需要用的，只有在分布式的时候，才有dubbo这样的分布式服务框架的需求。
下面将介绍如何搭建一个简单的示例程序（用maven构建）。
众所周知，RPC调用涉及到消费者、提供者和接口，所以需要在maven工程warehouse-component-parent里面新建3个模块，分别是warehouse-component-dubbo-facade（接口）、warehouse-component-dubbo-provider（提供者）和warehouse-component-dubbo-consumer（消费者）。对应的pom文件如下。
warehouse-component-parent：
<?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>org.wu</groupId> <artifactId>warehouse-component-parent</artifactId> <version>0.0.1</version> <packaging>pom</packaging> <name>component warehouse parent</name> <modules> <module>warehouse-component-dubbo-facade</module> <module>warehouse-component-dubbo-provider</module> <module>warehouse-component-dubbo-consumer</module> </modules> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <junit.version>4.12</junit.version> <spring.version>4.3.8.RELEASE</spring.version> <log4j.over.slf4j.version>1.7.25</log4j.over.slf4j.version> <jcl.over.slf4j.version>1.7.25</jcl.over.slf4j.version> <logback.version>1.2.3</logback.version> <dubbo.version>2.5.3</dubbo.version> <zkclient.version>0.1</zkclient.version> </properties> <dependencyManagement> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>${junit.version}</version> <scope>test</scope> </dependency> <!-- spring --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> <exclusions> <exclusion> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>${spring.version}</version> </dependency> <!-- logback --> <dependency> <groupId>org.slf4j</groupId> <artifactId>jcl-over-slf4j</artifactId> <version>${jcl.over.slf4j.version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> <version>${log4j.over.slf4j.version}</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>${logback.version}</version> </dependency> <!-- dubbo --> <dependency> <groupId>com.alibaba</groupId> <artifactId>dubbo</artifactId> <version>${dubbo.version}</version> <exclusions> <exclusion> <groupId>log4j</groupId> <artifactId>log4j</artifactId> </exclusion> <exclusion> <groupId>org.springframework</groupId> <artifactId>spring</artifactId> </exclusion> </exclusions> </dependency> <!-- zkclient --> <dependency> <groupId>com.github.sgroschupf</groupId> <artifactId>zkclient</artifactId> <version>${zkclient.version}</version> <exclusions> <exclusion> <groupId>log4j</groupId> <artifactId>log4j</artifactId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.wu</groupId> <artifactId>warehouse-component-dubbo-facade</artifactId> <version>${project.version}</version> </dependency> </dependencies> </dependencyManagement> </project>
warehouse-component-dubbo-provider：
<?xml version="1.0"?> <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.wu</groupId> <artifactId>warehouse-component-parent</artifactId> <version>0.0.1</version> </parent> <artifactId>warehouse-component-dubbo-provider</artifactId> <name>warehouse-component-dubbo-provider</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <scope>test</scope> </dependency> <!-- spring --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> </dependency> <!-- dubbo --> <dependency> <groupId>com.alibaba</groupId> <artifactId>dubbo</artifactId> </dependency> <!-- zkclient --> <dependency> <groupId>com.github.sgroschupf</groupId> <artifactId>zkclient</artifactId> </dependency> <!-- logback --> <dependency> <groupId>org.slf4j</groupId> <artifactId>jcl-over-slf4j</artifactId> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> </dependency> <dependency> <groupId>org.wu</groupId> <artifactId>warehouse-component-dubbo-facade</artifactId> </dependency> </dependencies> </project>
warehouse-component-dubbo-consumer：
<?xml version="1.0"?> <project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <modelVersion>4.0.0</modelVersion> <parent> <groupId>org.wu</groupId> <artifactId>warehouse-component-parent</artifactId> <version>0.0.1</version> </parent> <artifactId>warehouse-component-dubbo-consumer</artifactId> <name>warehouse-component-dubbo-consumer</name> <url>http://maven.apache.org</url> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <scope>test</scope> </dependency> <!-- spring --> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> </dependency> <!-- dubbo --> <dependency> <groupId>com.alibaba</groupId> <artifactId>dubbo</artifactId> </dependency> <!-- zkclient --> <dependency> <groupId>com.github.sgroschupf</groupId> <artifactId>zkclient</artifactId> </dependency> <!-- logback --> <dependency> <groupId>org.slf4j</groupId> <artifactId>jcl-over-slf4j</artifactId> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> </dependency> <dependency> <groupId>org.wu</groupId> <artifactId>warehouse-component-dubbo-facade</artifactId> </dependency> </dependencies> </project>
工程使用的日志框架为logback，配置文件如下：
<?xml version="1.0" encoding="UTF-8" ?> <configuration scan="true" scanPeriod="3 seconds"> <statusListener class="ch.qos.logback.core.status.OnConsoleStatusListener" /> <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"> <layout class="ch.qos.logback.classic.PatternLayout"> <!--格式化输出：%d表示日期，%thread表示线程名，%-5level：级别从左显示5个字符宽度%msg：日志消息，%n是换行符--> <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%-5level] [%logger:%L] %msg%n</pattern> </layout> </appender> <appender name="ALL_LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"> <File>warehouse_component.log</File> <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> <FileNamePattern> warehouse_component.%d{yyyy-MM-dd}.log </FileNamePattern> </rollingPolicy> <layout class="ch.qos.logback.classic.PatternLayout"> <!--格式化输出：%d表示日期，%thread表示线程名，%-5level：级别从左显示5个字符宽度%msg：日志消息，%n是换行符--> <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%-5level] [%logger:%L] %msg%n</pattern> </layout> </appender> <appender name="ERROR_LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"> <File>warehouse_component_error.log</File> <rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"> <FileNamePattern> warehouse_component_error.%d{yyyy-MM-dd}.log </FileNamePattern> </rollingPolicy> <filter class="ch.qos.logback.classic.filter.ThresholdFilter"> <level>ERROR</level> </filter> <layout class="ch.qos.logback.classic.PatternLayout"> <!--格式化输出：%d表示日期，%thread表示线程名，%-5level：级别从左显示5个字符宽度%msg：日志消息，%n是换行符--> <pattern>%d{yyyy-MM-dd HH:mm:ss.SSS} [%thread] [%-5level] [%logger:%L] %msg%n</pattern> </layout> </appender> <root> <level value="INFO" /> <appender-ref ref="STDOUT" /> <appender-ref ref="ALL_LOG_FILE" /> <appender-ref ref="ERROR_LOG_FILE" /> </root> </configuration>
上述配置信息都设置好后，就可以进行dubbo程序的开发了。首先，定义dubbo接口，在warehouse-component-dubbo-facade模块中定义一个接口：
package org.warehouse.component.dubbo.facade; public interface DemoFacade { /** * dubbo接口 */ String sayHello(String name); }
接口定义好后，dubbo服务提供者warehouse-component-dubbo-provider需要实现该接口，进行相关的业务逻辑处理。
package org.warehouse.component.dubbo.provider; import java.text.SimpleDateFormat; import java.util.Date; import org.springframework.stereotype.Service; import org.warehouse.component.dubbo.facade.DemoFacade; import com.alibaba.dubbo.rpc.RpcContext; @Service("demoFacadeImpl") public class DemoFacadeImpl implements DemoFacade { @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(); } }
并通过spring配置文件（dubbo-provider.xml）暴露该服务：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> <!-- 自动检测并装配bean --> <context:component-scan base-package="org.warehouse.component.dubbo.provider" /> <!-- 提供方应用信息，用于计算依赖关系 --> <dubbo:application name="provider-of-hello-world-app" /> <!-- 使用zookeeper注册中心暴露服务地址 --> <dubbo:registry protocol="zookeeper" address="192.168.1.103:2181" /> <!-- 用dubbo协议在20880端口暴露服务 --> <dubbo:protocol name="dubbo" port="20880" /> <!-- 声明需要暴露的服务接口 --> <dubbo:service interface="org.warehouse.component.dubbo.facade.DemoFacade" ref="demoFacadeImpl" /> </beans>
现在可以通过加载spring配置启动服务提供者了（运行以下代码）：
package org.warehouse.component.dubbo.provider; import java.io.IOException; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Provider { public static void main(String[] args) throws IOException { @SuppressWarnings("resource") ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("dubbo-provider.xml"); context.start(); System.in.read(); } }
服务提供者启动之后，服务消费者通过spring配置（dubbo-consumer.xml）引用远程服务：
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.3.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.3.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd"> <!-- 自动检测并装配bean --> <context:component-scan base-package="org.warehouse.component.dubbo.consumer" /> <!-- 提供方应用信息，用于计算依赖关系 --> <dubbo:application name="consumer-of-hello-world-app" /> <!-- 使用zookeeper注册中心暴露服务地址 --> <dubbo:registry protocol="zookeeper" address="192.168.1.103:2181" /> <dubbo:reference id="demoFacade" interface="org.warehouse.component.dubbo.facade.DemoFacade" /> </beans>
加载Spring配置，并调用远程服务（这里是通过spring unit test的方式）：
package org.warehouse.component.dubbo.consumer; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.warehouse.component.dubbo.facade.DemoFacade; @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = {"classpath:dubbo-consumer.xml"}) public class ConsumerTest { @Autowired ApplicationContext context; @Test public void testDemoFacade() { DemoFacade facade = (DemoFacade) context.getBean("demoFacade"); String hello = facade.sayHello("world"); System.out.println(hello); } }
服务的调用就像是方法本地调用一样简单，这其实是dubbo将底层通信封装好了，我们只需要关注业务逻辑实现。
在spring文件中配置dubbo服务时，eclipse会出现无法找到dubbo.xsd文件的问题。在本工程的解决办法是将dubbo-2.5.3.jar包中的dubbo.xsd文件（META-INF文件夹中）复制到文件系统中，然后
windows -> Preferrences -> XML -> XML Catalog
Add -> Catalog Entry -> File System 选择刚刚下载的文件路径
修改key值和配置文件的http://code.alibabatech.com/schema/dubbo/dubbo.xsd 相同
保存。。在xml文件右键validate ok解决了。
最后还有一点需要说明：dubbo和zkclient需要排除对log4j的依赖后才可以使用logback来记录详细日志，具体排除方式已经在warehouse-component-parent的pom文件中展示。
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