Dubbo学习（二）- Dubbo的hello world

左手的ㄟ右手 2022-05-27 00:05 180阅读 0赞

## 项目说明 ##

**Dubbo-Demo**  
dubbo的消费者，负责调用服务

**Dubbo-Hello-Api**  
标准api接口，避免服务提供者和消费者书写重复的代码

**Dubbo-Hello-Service**  
dubbo的服务者，提供服务共其他应用调用

## Dubbo-Hello-Api ##

**myeclipse中，右键》new》other》maven project，如下**  
![这里写图片描述][70]  
![这里写图片描述][70 1]  
**修改pom.xml**

**创建com.ahut.hello.service包，添加如下接口**

package com.ahut.hello.service;
    
    /** * * @ClassName: HelloService * @Description: Hello业务逻辑接口 * @author cheng * @date 2018年4月8日 上午11:25:18 */
    public interface HelloService { 
    
        /** * * @Title: sayHello * @Description: * @param name */
        void sayHello(String name);
    
    }

**发布项目到maven本地仓库**  
**选中项目》右键，run as》run configuration》maven build**  
![这里写图片描述][70 2]

## Dubbo-Hello-Service ##

**创建Dubbo-Hello-Service项目，和Dubbo-Hello-Api一样，参考上面**  
**修改pom.xml**

<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.ahut</groupId>
        <artifactId>Dubbo-Hello-Service</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <dependencies>
    
            
            <dependency>
                <groupId>com.ahut</groupId>
                <artifactId>Dubbo-Hello-Api</artifactId>
                <version>0.0.1-SNAPSHOT</version>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>dubbo</artifactId>
                <version>2.6.1</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.zookeeper</groupId>
                <artifactId>zookeeper</artifactId>
                <version>3.4.11</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.curator</groupId>
                <artifactId>curator-recipes</artifactId>
                <version>4.0.1</version>
            </dependency>
    
        </dependencies>
        <build>
            <plugins>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </project>

**创建com.ahut.hello.serviceImpl包，添加如下实现**

package com.ahut.hello.serviceImpl;
    
    import com.ahut.hello.service.HelloService;
    
    /** * * @ClassName: HelloServiceImpl * @Description: Hello业务逻辑实现 * @author cheng * @date 2018年4月8日 上午11:39:48 */
    public class HelloServiceImpl implements HelloService { 
    
        /** * 实现 */
        @Override
        public void sayHello(String name) {
            System.out.println("Hello " + name);
        }
    
    }

**添加spring-dubbo.xml配置**

<?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:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd ">
    
        <dubbo:application name="dubbo-hello" />
    
        
        <dubbo:registry address="zookeeper://127.0.0.1:2181" />
    
        <dubbo:protocol name="dubbo" port="20880" />
    
        
        <bean id="helloService" class="com.ahut.hello.serviceImpl.HelloServiceImpl" />
    
        
        <dubbo:service interface="com.ahut.hello.service.HelloService" ref="helloService" executes="10" />
    
    </beans>

**模拟启动服务，前提要开启zookeeper**

package com.ahut;
    
    import java.io.IOException;
    
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    /** * * @ClassName: ServiceMain * @Description: * @author cheng * @date 2018年4月8日 上午11:45:04 */
    public class ServiceMain { 
    
        public static void main(String[] args) throws IOException {
    
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                    new String[] { "spring-dubbo.xml" });
            context.start();
    
            System.out.println("输入任意按键退出 ~ ");
            System.in.read();
            context.close();
        }
    
    }

## Dubbo-Demo ##

**创建Dubbo-Demo项目，和Dubbo-Hello-Api一样，参考上面**  
**修改pom.xml**

<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.ahut</groupId>
        <artifactId>Dubbo-Demo</artifactId>
        <version>0.0.1-SNAPSHOT</version>
        <dependencies>
    
            
            <dependency>
                <groupId>com.ahut</groupId>
                <artifactId>Dubbo-Hello-Api</artifactId>
                <version>0.0.1-SNAPSHOT</version>
            </dependency>
    
            
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>dubbo</artifactId>
                <version>2.6.1</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.zookeeper</groupId>
                <artifactId>zookeeper</artifactId>
                <version>3.4.11</version>
            </dependency>
    
            
            <dependency>
                <groupId>org.apache.curator</groupId>
                <artifactId>curator-recipes</artifactId>
                <version>4.0.1</version>
            </dependency>
    
        </dependencies>
        <build>
            <plugins>
                <plugin>
                    <artifactId>maven-compiler-plugin</artifactId>
                    <configuration>
                        <source>1.8</source>
                        <target>1.8</target>
                    </configuration>
                </plugin>
            </plugins>
        </build>
    </project>

**添加spring-dubbo.xml配置**

<?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:dubbo="http://code.alibabatech.com/schema/dubbo" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd ">
    
        <dubbo:application name="dubbo-demo" />
    
        
        <dubbo:registry address="zookeeper://127.0.0.1:2181" />
    
        
        <dubbo:reference id="helloService" interface="com.ahut.hello.service.HelloService" />
    
    </beans>

**模拟调用服务**

package com.ahut;
    
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    
    import com.ahut.hello.service.HelloService;
    
    /** * * @ClassName: DemoMain * @Description: * @author cheng * @date 2018年4月8日 上午11:51:15 */
    public class DemoMain { 
    
        public static void main(String[] args) {
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                    new String[] { "spring-dubbo.xml" });
            context.start();
            HelloService helloService = (HelloService) context.getBean("helloService");
            helloService.sayHello("world");
    
            context.close();
        }
    
    }

## 可能出现的问题 ##

**Dubbo-Hello-Api项目打包失败，出现如下错误**

[INFO] Scanning for projects...
    [WARNING] 
    [WARNING] Some problems were encountered while building the effective model for com.ahut:Dubbo-Hello-Api:jar:0.0.1-SNAPSHOT
    [WARNING] 'build.plugins.plugin.version' for org.apache.maven.plugins:maven-compiler-plugin is missing. @ line 10, column 12
    [WARNING] 
    [WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
    [WARNING] 
    [WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
    [WARNING] 
    [INFO] ------------------------------------------------------------------------
    [INFO] BUILD FAILURE
    [INFO] ------------------------------------------------------------------------
    [INFO] Total time: 0.096 s
    [INFO] Finished at: 2018-04-08T14:32:14+08:00
    [INFO] Final Memory: 6M/155M
    [INFO] ------------------------------------------------------------------------
    [ERROR] No goals have been specified for this build. You must specify a valid lifecycle phase or a goal in the format <plugin-prefix>:<goal> or <plugin-group-id>:<plugin-artifact-id>[:<plugin-version>]:<goal>. Available lifecycle phases are: validate, initialize, generate-sources, process-sources, generate-resources, process-resources, compile, process-classes, generate-test-sources, process-test-sources, generate-test-resources, process-test-resources, test-compile, process-test-classes, test, prepare-package, package, pre-integration-test, integration-test, post-integration-test, verify, install, deploy, pre-clean, clean, post-clean, pre-site, site, post-site, site-deploy. -> [Help 1]
    [ERROR] 
    [ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
    [ERROR] Re-run Maven using the -X switch to enable full debug logging.
    [ERROR] 
    [ERROR] For more information about the errors and possible solutions, please read the following articles:
    [ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/NoGoalSpecifiedException

**解决办法：修改pom.xml文件，添加默认全局**

**Dubbo-Hello-Service或者Dubbo-Demo模拟启动失败，如下**

log4j:WARN No appenders could be found for logger (org.springframework.core.env.StandardEnvironment).
    log4j:WARN Please initialize the log4j system properly.
    log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
    Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/curator/RetryPolicy
        at com.alibaba.dubbo.remoting.zookeeper.curator.CuratorZookeeperTransporter.connect(CuratorZookeeperTransporter.java:26)
        at com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter$Adaptive.connect(ZookeeperTransporter$Adaptive.java)
        at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistry.<init>(ZookeeperRegistry.java:69)
        at com.alibaba.dubbo.registry.zookeeper.ZookeeperRegistryFactory.createRegistry(ZookeeperRegistryFactory.java:37)
        at com.alibaba.dubbo.registry.support.AbstractRegistryFactory.getRegistry(AbstractRegistryFactory.java:95)
        at com.alibaba.dubbo.registry.RegistryFactory$Adaptive.getRegistry(RegistryFactory$Adaptive.java)
        at com.alibaba.dubbo.registry.integration.RegistryProtocol.getRegistry(RegistryProtocol.java:200)
        at com.alibaba.dubbo.registry.integration.RegistryProtocol.export(RegistryProtocol.java:134)
        at com.alibaba.dubbo.rpc.protocol.ProtocolListenerWrapper.export(ProtocolListenerWrapper.java:54)
        at com.alibaba.dubbo.rpc.protocol.ProtocolFilterWrapper.export(ProtocolFilterWrapper.java:91)
        at com.alibaba.dubbo.qos.protocol.QosProtocolWrapper.export(QosProtocolWrapper.java:54)
        at com.alibaba.dubbo.rpc.Protocol$Adaptive.export(Protocol$Adaptive.java)
        at com.alibaba.dubbo.config.ServiceConfig.doExportUrlsFor1Protocol(ServiceConfig.java:505)
        at com.alibaba.dubbo.config.ServiceConfig.doExportUrls(ServiceConfig.java:357)
        at com.alibaba.dubbo.config.ServiceConfig.doExport(ServiceConfig.java:316)
        at com.alibaba.dubbo.config.ServiceConfig.export(ServiceConfig.java:215)
        at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:121)
        at com.alibaba.dubbo.config.spring.ServiceBean.onApplicationEvent(ServiceBean.java:50)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
        at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
        at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:393)
        at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:347)
        at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:883)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546)
        at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
        at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93)
        at com.ahut.ServiceMain.main(ServiceMain.java:18)
    Caused by: java.lang.ClassNotFoundException: org.apache.curator.RetryPolicy
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        ... 27 more

**解决办法：修改pom.xml，引入缺少的jar**

[70]: /images/20220527/fde24dbfe65a4ef1a2a18b0e761721c3.png
[70 1]: /images/20220527/038f8573f1ef4778bc37212acd870fbe.png
[70 2]: /images/20220527/8d537abf1d144a1aa289b4484e63c5c5.png