Dubbo3.0入门-Java版

Dubbo 简介

Apache Dubbo 是一款 RPC 服务开发框架，用于解决微服务架构下的服务治理与通信问题，官方提供了 Java、Golang 等多语言 SDK 实现。使用 Dubbo 开发的微服务原生具备相互之间的远程地址发现与通信能力，利用 Dubbo 提供的丰富服务治理特性，可以实现诸如服务发现、负载均衡、流量调度等服务治理诉求。Dubbo 被设计为高度可扩展，用户可以方便的实现流量拦截、选址的各种定制逻辑。

Dubbo3 定义为面向云原生的下一代 RPC 服务框架。3.0 基于 Dubbo 2.x 演进而来，在保持原有核心功能特性的同时， Dubbo3 在易用性、超大规模微服务实践、云原生基础设施适配、安全性等几大方向上进行了全面升级。

Dobbo的基本工作流程

由上图可知要使用dubbo完成一次RPC调用，需要定义三类对象：

服务接口
生产者：实现具体的服务接口
消费者：生成服务代理对象，实现在本地调用远程服务

下面开始dubbo的入门案例

总览项目框架

创建maven作为父项目

父项目设置为dubbo-study，并在父项目中配置dubbo依赖

<properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><spring.version>4.3.16.RELEASE</spring.version><dubbo.version>3.0.7</dubbo.version><junit.version>4.13.1</junit.version><slf4j-log4j12.version>1.7.25</slf4j-log4j12.version><spring-boot.version>2.3.1.RELEASE</spring-boot.version><spring-boot-maven-plugin.version>2.1.4.RELEASE</spring-boot-maven-plugin.version></properties><dependencyManagement><dependencies><!-- Spring Boot --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-dependencies</artifactId><version>${spring-boot.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-bom</artifactId><version>${dubbo.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-dependencies-zookeeper</artifactId><version>${dubbo.version}</version><type>pom</type></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><version>${junit.version}</version><scope>test</scope></dependency></dependencies></dependencyManagement><dependencies><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-api</artifactId></dependency><dependency><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId><version>${slf4j-log4j12.version}</version></dependency><dependency><groupId>log4j</groupId><artifactId>log4j</artifactId></dependency><dependency><groupId>junit</groupId><artifactId>junit</artifactId><scope>test</scope></dependency></dependencies>

编写服务接口

项目名：dubbo-springboot-interface
pom.xml

<?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"><parent><artifactId>dubbo-study</artifactId><groupId>com.mxf</groupId><version>1.0-SNAPSHOT</version><relativePath>../pom.xml</relativePath></parent><modelVersion>4.0.0</modelVersion><artifactId>dubbo-springboot-interface</artifactId><properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding></properties></project>

服务接口

编写服务生产者

项目名：dubbo-springboot-provider
项目结构

导入依赖：

<properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding></properties><dependencies><dependency><groupId>com.mxf</groupId><artifactId>dubbo-springboot-interface</artifactId><version>1.0-SNAPSHOT</version></dependency><!-- dubbo --><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo</artifactId></dependency><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-dependencies-zookeeper</artifactId><type>pom</type></dependency><!-- dubbo starter --><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-spring-boot-starter</artifactId></dependency><!-- spring starter --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-autoconfigure</artifactId></dependency></dependencies>

实现具体服务：

import com.mxf.service.HelloService;
import org.apache.dubbo.config.annotation.DubboService;
import org.apache.dubbo.rpc.RpcContext;/*** 用 @DubboService 注解标记，就可以实现 Dubbo 的服务暴露* 如果要设置服务参数，@DubboService 也提供了常用参数的设置方式。如果有更复杂的参数设置需求，则可以考虑使用其他设置方式* @DubboService(version = "1.0.0", group = "dev", timeout = 5000)*/
@DubboService
public class HelloServiceImpl implements HelloService {@Overridepublic String sayHello(String name) {System.out.println("Hello " + name + ", request from consumer: " + RpcContext.getContext().getRemoteAddress());return "Hello " + name;}
}

参考官网的内嵌ZooKeeper类

package com.mxf.config;import org.apache.zookeeper.server.ServerConfig;
import org.apache.zookeeper.server.ZooKeeperServerMain;
import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.SmartLifecycle;
import org.springframework.util.ErrorHandler;
import org.springframework.util.SocketUtils;import java.io.File;
import java.lang.reflect.Method;
import java.util.Properties;
import java.util.UUID;/*** from: https://github.com/spring-projects/spring-xd/blob/v1.3.1.RELEASE/spring-xd-dirt/src/main/java/org/springframework/xd/dirt/zookeeper/ZooKeeperUtils.java* <p>* Helper class to start an embedded instance of standalone (non clustered) ZooKeeper.* <p>* NOTE: at least an external standalone server (if not an ensemble) are recommended, even for* {@link org.springframework.xd.dirt.server.singlenode.SingleNodeApplication}** @author Patrick Peralta* @author Mark Fisher* @author David Turanski*/
public class EmbeddedZooKeeper implements SmartLifecycle {/*** Logger.*/private static final Logger logger = LoggerFactory.getLogger(EmbeddedZooKeeper.class);/*** ZooKeeper client port. This will be determined dynamically upon startup.*/private final int clientPort;/*** Whether to auto-start. Default is true.*/private boolean autoStartup = true;/*** Lifecycle phase. Default is 0.*/private int phase = 0;/*** Thread for running the ZooKeeper server.*/private volatile Thread zkServerThread;/*** ZooKeeper server.*/private volatile ZooKeeperServerMain zkServer;/*** {@link ErrorHandler} to be invoked if an Exception is thrown from the ZooKeeper server thread.*/private ErrorHandler errorHandler;private boolean daemon = true;/*** Construct an EmbeddedZooKeeper with a random port.*/public EmbeddedZooKeeper() {clientPort = SocketUtils.findAvailableTcpPort();}/*** Construct an EmbeddedZooKeeper with the provided port.** @param clientPort port for ZooKeeper server to bind to*/public EmbeddedZooKeeper(int clientPort, boolean daemon) {this.clientPort = clientPort;this.daemon = daemon;}/*** Returns the port that clients should use to connect to this embedded server.** @return dynamically determined client port*/public int getClientPort() {return this.clientPort;}/*** Specify whether to start automatically. Default is true.** @param autoStartup whether to start automatically*/public void setAutoStartup(boolean autoStartup) {this.autoStartup = autoStartup;}/*** {@inheritDoc}*/@Overridepublic boolean isAutoStartup() {return this.autoStartup;}/*** Specify the lifecycle phase for the embedded server.** @param phase the lifecycle phase*/public void setPhase(int phase) {this.phase = phase;}/*** {@inheritDoc}*/@Overridepublic int getPhase() {return this.phase;}/*** {@inheritDoc}*/@Overridepublic boolean isRunning() {return (zkServerThread != null);}/*** Start the ZooKeeper server in a background thread.* <p>* Register an error handler via {@link #setErrorHandler} in order to handle* any exceptions thrown during startup or execution.*/@Overridepublic synchronized void start() {if (zkServerThread == null) {zkServerThread = new Thread(new ServerRunnable(), "ZooKeeper Server Starter");zkServerThread.setDaemon(daemon);zkServerThread.start();}}/*** Shutdown the ZooKeeper server.*/@Overridepublic synchronized void stop() {if (zkServerThread != null) {// The shutdown method is protected...thus this hack to invoke it.// This will log an exception on shutdown; see// https://issues.apache.org/jira/browse/ZOOKEEPER-1873 for details.try {Method shutdown = ZooKeeperServerMain.class.getDeclaredMethod("shutdown");shutdown.setAccessible(true);shutdown.invoke(zkServer);} catch (Exception e) {throw new RuntimeException(e);}// It is expected that the thread will exit after// the server is shutdown; this will block until// the shutdown is complete.try {zkServerThread.join(5000);zkServerThread = null;} catch (InterruptedException e) {Thread.currentThread().interrupt();logger.warn("Interrupted while waiting for embedded ZooKeeper to exit");// abandoning zk threadzkServerThread = null;}}}/*** Stop the server if running and invoke the callback when complete.*/@Overridepublic void stop(Runnable callback) {stop();callback.run();}/*** Provide an {@link ErrorHandler} to be invoked if an Exception is thrown from the ZooKeeper server thread. If none* is provided, only error-level logging will occur.** @param errorHandler the {@link ErrorHandler} to be invoked*/public void setErrorHandler(ErrorHandler errorHandler) {this.errorHandler = errorHandler;}/*** Runnable implementation that starts the ZooKeeper server.*/private class ServerRunnable implements Runnable {@Overridepublic void run() {try {Properties properties = new Properties();File file = new File(System.getProperty("java.io.tmpdir")+ File.separator + UUID.randomUUID());file.deleteOnExit();properties.setProperty("dataDir", file.getAbsolutePath());properties.setProperty("clientPort", String.valueOf(clientPort));QuorumPeerConfig quorumPeerConfig = new QuorumPeerConfig();quorumPeerConfig.parseProperties(properties);zkServer = new ZooKeeperServerMain();ServerConfig configuration = new ServerConfig();configuration.readFrom(quorumPeerConfig);zkServer.runFromConfig(configuration);} catch (Exception e) {if (errorHandler != null) {errorHandler.handleError(e);} else {logger.error("Exception running embedded ZooKeeper", e);}}}}}

启动类

import com.mxf.config.EmbeddedZooKeeper;
import org.apache.dubbo.config.spring.context.annotation.EnableDubbo;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplication
@EnableDubbo    // @EnableDubbo 注解必须配置，否则将无法加载 Dubbo 注解定义的服务，@EnableDubbo 可以定义在主类上
public class ProviderApplication {public static void main(String[] args) {new EmbeddedZooKeeper(2181, false).start();SpringApplication.run(ProviderApplication.class, args);System.out.println("dubbo service started");
//        new CountDownLatch(1).await();}
}

对应的配置文件：

dubbo:application:name: dubbo-springboot-providerprotocol:name: dubboport: -1registry:id: zk-registryaddress: zookeeper://127.0.0.1:2181config-center:address: zookeeper://127.0.0.1:2181metadata-report:address: zookeeper://127.0.0.1:2181

服务消费者

项目名：dubbo-springboot-consumer
项目结构：

依赖：

 <properties><maven.compiler.source>8</maven.compiler.source><maven.compiler.target>8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><slf4j-log4j12.version>1.7.25</slf4j-log4j12.version><spring-boot.version>2.3.1.RELEASE</spring-boot.version></properties><dependencies><dependency><groupId>com.mxf</groupId><artifactId>dubbo-springboot-interface</artifactId><version>${project.parent.version}</version></dependency><!-- dubbo --><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo</artifactId></dependency><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-dependencies-zookeeper</artifactId><type>pom</type></dependency><!-- dubbo starter --><dependency><groupId>org.apache.dubbo</groupId><artifactId>dubbo-spring-boot-starter</artifactId></dependency><!-- spring starter --><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-autoconfigure</artifactId></dependency></dependencies>

在本地实现调用远程服务

@SpringBootApplication
@Service
@EnableDubbo
public class ConsumerApplication {/*** @Reference 注解从 3.0 版本开始就已经废弃，改用 @DubboReference，以区别于 Spring 的 @Reference 注解* @DubboReference 注解将自动注入为 Dubbo 服务代理实例，使用 helloService 即可发起远程服务调用*/@DubboReferenceprivate HelloService helloService;public String doSayHello(String name) {return helloService.sayHello(name);}public static void main(String[] args) {ConfigurableApplicationContext context = SpringApplication.run(ConsumerApplication.class, args);ConsumerApplication application = context.getBean(ConsumerApplication.class);String result = application.doSayHello("world");System.out.println("result: " + result);}
}

运行演示

首先启动dubbo-springboot-provider远程服务提供者

然后启动dubbo-springboot-consumer服务消费者
先看到服务提供者，打印接收到请求的日志：

消费者获取到服务提供者的处理结果

总结

step1: 编写远程服务接口
step2: 编写服务提供者
1. 实现远程服务接口
2. 使用@DubboService将服务暴露
step3: 编写服务消费者
1. 使用@DubboReference获取特定的服务实现类
2. 通过获取到的服务实现类来发起远程调用