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：

1. 服务接口
2. 生产者：实现具体的服务接口
3. 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>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <spring.version>4.3.16.RELEASEspring.version>
        <dubbo.version>3.0.7dubbo.version>
        <junit.version>4.13.1junit.version>
        <slf4j-log4j12.version>1.7.25slf4j-log4j12.version>
        <spring-boot.version>2.3.1.RELEASEspring-boot.version>
        <spring-boot-maven-plugin.version>2.1.4.RELEASEspring-boot-maven-plugin.version>
    properties>

    <dependencyManagement>
        <dependencies>
            
            <dependency>
                <groupId>org.springframework.bootgroupId>
                <artifactId>spring-boot-dependenciesartifactId>
                <version>${spring-boot.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>

            <dependency>
                <groupId>org.apache.dubbogroupId>
                <artifactId>dubbo-bomartifactId>
                <version>${dubbo.version}version>
                <type>pomtype>
                <scope>importscope>
            dependency>

            <dependency>
                <groupId>org.apache.dubbogroupId>
                <artifactId>dubbo-dependencies-zookeeperartifactId>
                <version>${dubbo.version}version>
                <type>pomtype>
            dependency>

            <dependency>
                <groupId>junitgroupId>
                <artifactId>junitartifactId>
                <version>${junit.version}version>
                <scope>testscope>
            dependency>
        dependencies>
    dependencyManagement>

    <dependencies>
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-apiartifactId>
        dependency>
        <dependency>
            <groupId>org.slf4jgroupId>
            <artifactId>slf4j-log4j12artifactId>
            <version>${slf4j-log4j12.version}version>
        dependency>
        <dependency>
            <groupId>log4jgroupId>
            <artifactId>log4jartifactId>
        dependency>

        <dependency>
            <groupId>junitgroupId>
            <artifactId>junitartifactId>
            <scope>testscope>
        dependency>
    dependencies>

编写服务接口

项目名：dubbo-springboot-interface
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">
    <parent>
        <artifactId>dubbo-studyartifactId>
        <groupId>com.mxfgroupId>
        <version>1.0-SNAPSHOTversion>
        <relativePath>../pom.xmlrelativePath>
    parent>
    <modelVersion>4.0.0modelVersion>

    <artifactId>dubbo-springboot-interfaceartifactId>

    <properties>
        <maven.compiler.source>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.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>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
    properties>

    <dependencies>
        <dependency>
            <groupId>com.mxfgroupId>
            <artifactId>dubbo-springboot-interfaceartifactId>
            <version>1.0-SNAPSHOTversion>
        dependency>

        
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubboartifactId>
        dependency>
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubbo-dependencies-zookeeperartifactId>
            <type>pomtype>
        dependency>

        
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubbo-spring-boot-starterartifactId>
        dependency>

        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starterartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-autoconfigureartifactId>
        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 {
    @Override
    public 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
 * 

 * Helper class to start an embedded instance of standalone (non clustered) ZooKeeper.
 * 

 * 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}
     */
    @Override
    public 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}
     */
    @Override
    public int getPhase() {
        return this.phase;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isRunning() {
        return (zkServerThread != null);
    }

    /**
     * Start the ZooKeeper server in a background thread.
     * 

     * Register an error handler via {@link #setErrorHandler} in order to handle
     * any exceptions thrown during startup or execution.
     */
    @Override
    public synchronized void start() {
        if (zkServerThread == null) {
            zkServerThread = new Thread(new ServerRunnable(), "ZooKeeper Server Starter");
            zkServerThread.setDaemon(daemon);
            zkServerThread.start();
        }
    }

    /**
     * Shutdown the ZooKeeper server.
     */
    @Override
    public 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 thread
                zkServerThread = null;
            }
        }
    }

    /**
     * Stop the server if running and invoke the callback when complete.
     */
    @Override
    public 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 {

        @Override
        public 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-provider
  protocol:
    name: dubbo
    port: -1
  registry:
    id: zk-registry
    address: zookeeper://127.0.0.1:2181
  config-center:
    address: zookeeper://127.0.0.1:2181
  metadata-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>8maven.compiler.source>
        <maven.compiler.target>8maven.compiler.target>
        <project.build.sourceEncoding>UTF-8project.build.sourceEncoding>
        <slf4j-log4j12.version>1.7.25slf4j-log4j12.version>
        <spring-boot.version>2.3.1.RELEASEspring-boot.version>
    properties>

    <dependencies>
        <dependency>
            <groupId>com.mxfgroupId>
            <artifactId>dubbo-springboot-interfaceartifactId>
            <version>${project.parent.version}version>
        dependency>

        
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubboartifactId>
        dependency>
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubbo-dependencies-zookeeperartifactId>
            <type>pomtype>
        dependency>

        
        <dependency>
            <groupId>org.apache.dubbogroupId>
            <artifactId>dubbo-spring-boot-starterartifactId>
        dependency>

        
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-starterartifactId>
        dependency>
        <dependency>
            <groupId>org.springframework.bootgroupId>
            <artifactId>spring-boot-autoconfigureartifactId>
        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
     */
    @DubboReference
    private 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