dubbo的调用原理及泛化调用

落日映苍穹つ 2023-02-19 12:27 11阅读 0赞

### 简单介绍 ###

dubbo是阿里开源出来的一个rpc框架，主要是用于微服务分布式项目的远程调用，它提供了三大核心能力：面向接口的远程方法调用，智能容错和负载均衡，以及服务自动注册和发现，下面是调用的原理图：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NTEzNDMw_size_16_color_FFFFFF_t_70]  
dubbo框架的整体设计：  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NTEzNDMw_size_16_color_FFFFFF_t_70 1]  
图例说明：

1，图中左边淡蓝背景的为服务消费方使用的接口，右边淡绿色背景的为服务提供方使用的接口，位于中轴线上的为双方都用到的接口。  
2，图中从下至上分为十层，各层均为单向依赖，右边的黑色箭头代表层之间的依赖关系，每一层都可以剥离上层被复用，其中，Service 和 Config 层为 API，其它各层均为 SPI。  
3，图中绿色小块的为扩展接口，蓝色小块为实现类，图中只显示用于关联各层的实现类。  
4，图中蓝色虚线为初始化过程，即启动时组装链，红色实线为方法调用过程，即运行时调时链，紫色三角箭头为继承，可以把子类看作父类的同一个节点，线上的文字为调用的方法

### 远程调用细节 ###

###### 服务提供者暴露一个服务的详细过程 ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NTEzNDMw_size_16_color_FFFFFF_t_70 2]  
上图是服务提供者暴露服务的主过程：

首先 ServiceConfig 类拿到对外提供服务的实际类 ref(如：HelloWorldImpl),然后通过 ProxyFactory 类的 getInvoker 方法使用 ref 生成一个 AbstractProxyInvoker 实例，到这一步就完成具体服务到 Invoker 的转化。接下来就是 Invoker 转换到 Exporter 的过程。

Dubbo 处理服务暴露的关键就在 Invoker 转换到 Exporter 的过程，上图中的红色部分。下面我们以 Dubbo 和 RMI 这两种典型协议的实现来进行说明：

Dubbo 的实现  
Dubbo 协议的 Invoker 转为 Exporter 发生在 DubboProtocol 类的 export 方法，它主要是打开 socket 侦听服务，并接收客户端发来的各种请求，通讯细节由 Dubbo 自己实现。

RMI 的实现  
RMI 协议的 Invoker 转为 Exporter 发生在 RmiProtocol类的 export 方法，它通过 Spring 或 Dubbo 或 JDK 来实现 RMI 服务，通讯细节这一块由 JDK 底层来实现，这就省了不少工作量。

###### 服务消费者消费一个服务的详细过程 ######

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5NTEzNDMw_size_16_color_FFFFFF_t_70 3]  
上图是服务消费的主过程：

首先 ReferenceConfig 类的 init 方法调用 Protocol 的 refer 方法生成 Invoker 实例(如上图中的红色部分)，这是服务消费的关键。接下来把 Invoker 转换为客户端需要的接口(如：HelloWorld)。

### dubbo直接引用 ###

###### 1，xml形式 ######

服务提供者：

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

具体实现：

public class DemoServiceImpl implements DemoService {
        
        public String sayHello(String name) {
        
            return "Hello " + name;
        }
    }

spring声明暴露服务：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
        xsi:schemaLocation="http://www.springframework.org/schema/beans        http://www.springframework.org/schema/beans/spring-beans-4.3.xsd        http://dubbo.apache.org/schema/dubbo        http://dubbo.apache.org/schema/dubbo/dubbo.xsd">
     
        
        <dubbo:application name="hello-world-app"  />
     
        
        <dubbo:registry address="multicast://224.5.6.7:1234" />
     
        
        <dubbo:protocol name="dubbo" port="20880" />
     
        
        <dubbo:service interface="org.apache.dubbo.demo.DemoService" ref="demoService" />
     
        
        <bean id="demoService" class="org.apache.dubbo.demo.provider.DemoServiceImpl" />
    </beans>

服务消费者：  
通过 Spring 配置引用远程服务：

<?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:dubbo="http://dubbo.apache.org/schema/dubbo"
        xsi:schemaLocation="http://www.springframework.org/schema/beans        http://www.springframework.org/schema/beans/spring-beans-4.3.xsd        http://dubbo.apache.org/schema/dubbo        http://dubbo.apache.org/schema/dubbo/dubbo.xsd">
     
        
        <dubbo:application name="consumer-of-helloworld-app"  />
     
        
        <dubbo:registry address="multicast://224.5.6.7:1234" />
     
        
        <dubbo:reference id="demoService" interface="org.apache.dubbo.demo.DemoService" />
    </beans>

远程调用：

public class Consumer {
        
        public static void main(String[] args) throws Exception {
        
            ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[] {
        "http://10.20.160.198/wiki/display/dubbo/consumer.xml"});
            context.start();
            DemoService demoService = (DemoService)context.getBean("demoService"); // 获取远程服务代理
            String hello = demoService.sayHello("world"); // 执行远程方法
            System.out.println( hello ); // 显示调用结果
        }
    }

###### 2，api形式 ######

提供者暴露服务：

/**
     * @author shihaowei
     * @date 2020-06-11 11:43
     */
    @Configuration
    //@EnableDubbo
    @DubboComponentScan("person.shw.dubbo.provider")
    public class DubboConfig {
        
    
        @Value("${nacos.data.id:f21d3b6b-20ed-4091-ab17-ac073abc3eba}")
        private String namespace;
    
        @Bean
        public ApplicationConfig applicationConfig(){
        
            ApplicationConfig applicationConfig = new ApplicationConfig();
            applicationConfig.setName("provider-nacos");
            return applicationConfig;
        }
    
        @Bean
        public RegistryConfig registryConfig(){
        
            RegistryConfig registryConfig = new RegistryConfig();
            registryConfig.setAddress("nacos://120.79.76.230:8848");
            registryConfig.setGroup("ONE_GROUP");
            Map<String,String> paramMap = new HashMap<String, String>();
            paramMap.put("namespace",namespace);
            registryConfig.setParameters(paramMap);
            return registryConfig;
        }
    
    
        @Bean
        public ProtocolConfig protocolConfig(){
        
            ProtocolConfig protocolConfig = new ProtocolConfig();
            protocolConfig.setName("dubbo");
            protocolConfig.setPort(12347);
            return protocolConfig;
        }
    
    }

暴露服务的接口实现：

import org.apache.dubbo.config.annotation.Service;
    import person.shw.dubbo.api.DubboApi;
    
    /**
     * @author shihaowei
     * @date 2020-06-09 17:21
     */
    @Service
    public class ProviderServiceImpl implements DubboApi {
        
        public String getConsumerData() {
        
            return "333333333333333333";
        }
    }

**org.apache.dubbo.config.annotation.Service是引用的dubbo的包，而不是Spring的@Service**

消费者消费服务：

@Configuration
    public class DubboNacosConfig {
        
    
        @Bean
        public ApplicationConfig applicationConfig(RegistryConfig registryConfig){
        
            ApplicationConfig applicationConfig = new ApplicationConfig();
            applicationConfig.setName("consumer-nacos");
            applicationConfig.setRegistry(registryConfig);
            return applicationConfig;
        }
    
        @Bean
        public RegistryConfig registryConfig(){
        
            RegistryConfig registryConfig = new RegistryConfig();
            registryConfig.setCheck(false);
            registryConfig.setAddress("nacos://120.79.76.230:8848");
            registryConfig.setUsername("nacos");
            registryConfig.setPassword("nacos");
            Map<String,String> paramMap = new HashMap<String, String>();
            paramMap.put("namespace","f21d3b6b-20ed-4091-ab17-ac073abc3eba");
            registryConfig.setParameters(paramMap);
            return registryConfig;
        }
    }

调用服务

import org.apache.dubbo.config.annotation.Reference;
    import org.springframework.web.bind.annotation.GetMapping;
    import org.springframework.web.bind.annotation.RestController;
    import person.shw.dubbo.api.DubboApi;
    
    /**
     * @author shihaowei
     * @date 2020-06-09 17:22
     */
    @RestController
    public class ConsumerController {
        
    
        @Reference
        private DubboApi dubboApi;
    
        @GetMapping(value = "/consumer/getMessage")
        public String getMessage(){
        
            return "【收到发来的消息】---->"+dubboApi.getConsumerData();
        }
    
    }

### dubbo的泛化调用 ###

为什么要使用泛化调用？

一般使用dubbo，provider端需要暴露出接口和方法，consumer端要十分明确服务使用的接口定义和方法定义（还有入参返参类型等等信息，常常还需要基于provider端提供的API），两端才能正常通信调用。

然而存在一种使用场景，调用方并不关心要调用的接口的详细定义，它只关注我要调用哪个方法，需要传什么参数，我能接收到什么返回结果即可，这样可以大大降低consumer端和provider端的耦合性。

所以为了应对以上的需求，dubbo提供了泛化调用，也就是在consumer只知道一个接口全限定名以及入参和返参的情况下，就可以调用provider端的调用，而不需要传统的接口定义这些繁杂的结构。

比如微服务的网关就可以采用泛化调用，又不需要强引用众多需要调用的服务

### 例子 ###

继续使用上面使用api的配置，当我调用的时候，不时用@reference注解，而是用genericservice泛化调用，参数及返回值中的所有 POJO 均用 Map 表示，通常用于框架集成

@RestController
    public class ConsumerController {
        
    
        @Autowired
        private ApplicationConfig applicationConfig;
    
        @GetMapping(value = "/consumer/getMessage")
        public String getMessage(){
        
            /** dubbo的泛化调用 */
            ReferenceConfig<GenericService> reference = new ReferenceConfig<GenericService>();
            reference.setApplication(applicationConfig);
            reference.setInterface("person.shw.dubbo.api.DubboApi");
            reference.setTimeout(200000);
            reference.setGeneric(true);
            /** 添加缓存策略 */
            /*ReferenceConfigCache cache = ReferenceConfigCache.getCache();
            GenericService genericService = cache.get(reference);*/
            GenericService genericService = reference.get();
    
            /** 设置接口所需要的参数类型 */
            String[] parametertypes = new String[]{
        };
            String[] args = new String[]{
        };
            Object data = genericService.$invoke("getConsumerData", parametertypes, args);
            System.out.println(JSON.toJSONString(data));
            return "【收到consumer发来的消息】---->"+JSON.toJSONString(data);
        }
    
    }

调用服务，打印日志

2020-06-20 17:44:25.482  INFO 3033 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 924 ms
    2020-06-20 17:44:25.664  WARN 3033 --- [           main] org.apache.dubbo.config.AbstractConfig   :  [DUBBO] There's no valid metadata config found, if you are using the simplified mode of registry url, please make sure you have a metadata address configured properly., dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:25.669  INFO 3033 --- [           main] org.apache.dubbo.config.AbstractConfig   :  [DUBBO] There's no valid monitor config found, if you want to open monitor statistics for Dubbo, please make sure your monitor is configured properly., dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:25.689  INFO 3033 --- [           main] o.a.d.qos.protocol.QosProtocolWrapper    :  [DUBBO] qos won't be started because it is disabled. Please check dubbo.application.qos.enable is configured either in system property, dubbo.properties or XML/spring-boot configuration., dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:25.786  INFO 3033 --- [           main] o.a.dubbo.registry.nacos.NacosRegistry   :  [DUBBO] Load registry cache file /Users/edz/.dubbo/dubbo-registry-consumer-nacos-120.79.76.230:8848.cache, data: {person.shw.dubbo.api.DubboApi=dubbo://192.168.31.132:12347/person.shw.dubbo.api.DubboApi?anyhost=true&application=provider-nacos&bean.name=ServiceBean:person.shw.dubbo.api.DubboApi&category=providers&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=person.shw.dubbo.api.DubboApi&methods=getConsumerData&path=person.shw.dubbo.api.DubboApi&pid=2846&protocol=dubbo&register=true&release=2.7.3&side=provider&timestamp=1592646130152}, dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:25.804  INFO 3033 --- [           main] o.a.dubbo.registry.nacos.NacosRegistry   :  [DUBBO] Register: consumer://192.168.31.132/org.apache.dubbo.rpc.service.GenericService?application=consumer-nacos&category=consumers&check=false&dubbo=2.0.2&generic=true&interface=person.shw.dubbo.api.DubboApi&lazy=false&pid=3033&qos.enable=false&release=2.7.3&side=consumer&sticky=false&timeout=200000&timestamp=1592646265664, dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:25.967  INFO 3033 --- [           main] o.a.dubbo.registry.nacos.NacosRegistry   :  [DUBBO] Subscribe: consumer://192.168.31.132/org.apache.dubbo.rpc.service.GenericService?application=consumer-nacos&category=providers,configurators,routers&dubbo=2.0.2&generic=true&interface=person.shw.dubbo.api.DubboApi&lazy=false&pid=3033&qos.enable=false&release=2.7.3&side=consumer&sticky=false&timeout=200000&timestamp=1592646265664, dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:26.009  INFO 3033 --- [           main] o.a.dubbo.registry.nacos.NacosRegistry   :  [DUBBO] Notify urls for subscribe url consumer://192.168.31.132/org.apache.dubbo.rpc.service.GenericService?application=consumer-nacos&category=providers,configurators,routers&dubbo=2.0.2&generic=true&interface=person.shw.dubbo.api.DubboApi&lazy=false&pid=3033&qos.enable=false&release=2.7.3&side=consumer&sticky=false&timeout=200000&timestamp=1592646265664, urls: [dubbo://192.168.31.132:12347/person.shw.dubbo.api.DubboApi?anyhost=true&application=provider-nacos&bean.name=ServiceBean:person.shw.dubbo.api.DubboApi&category=providers&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=person.shw.dubbo.api.DubboApi&methods=getConsumerData&path=person.shw.dubbo.api.DubboApi&pid=2846&protocol=dubbo&register=true&release=2.7.3&side=provider&timestamp=1592646130152], dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:26.181  INFO 3033 --- [           main] o.a.d.remoting.transport.AbstractClient  :  [DUBBO] Succeed connect to server /192.168.31.132:12347 from NettyClient 192.168.31.132 using dubbo version 2.7.3, channel is NettyChannel [channel=[id: 0x5cf0891f, L:/192.168.31.132:55666 - R:/192.168.31.132:12347]], dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:26.181  INFO 3033 --- [           main] o.a.d.remoting.transport.AbstractClient  :  [DUBBO] Start NettyClient /192.168.31.132 connect to the server /192.168.31.132:12347, dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:26.216  INFO 3033 --- [client.listener] o.a.dubbo.registry.nacos.NacosRegistry   :  [DUBBO] Notify urls for subscribe url consumer://192.168.31.132/org.apache.dubbo.rpc.service.GenericService?application=consumer-nacos&category=providers,configurators,routers&dubbo=2.0.2&generic=true&interface=person.shw.dubbo.api.DubboApi&lazy=false&pid=3033&qos.enable=false&release=2.7.3&side=consumer&sticky=false&timeout=200000&timestamp=1592646265664, urls: [dubbo://192.168.31.132:12347/person.shw.dubbo.api.DubboApi?anyhost=true&application=provider-nacos&bean.name=ServiceBean:person.shw.dubbo.api.DubboApi&category=providers&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=person.shw.dubbo.api.DubboApi&methods=getConsumerData&path=person.shw.dubbo.api.DubboApi&pid=2846&protocol=dubbo&register=true&release=2.7.3&side=provider&timestamp=1592646130152], dubbo version: 2.7.3, current host: 192.168.31.132
    2020-06-20 17:44:26.218  INFO 3033 --- [           main] org.apache.dubbo.config.AbstractConfig   :  [DUBBO] Refer dubbo service org.apache.dubbo.rpc.service.GenericService from url nacos://120.79.76.230:8848/org.apache.dubbo.registry.RegistryService?anyhost=true&application=consumer-nacos&bean.name=ServiceBean:person.shw.dubbo.api.DubboApi&category=providers&check=false&deprecated=false&dubbo=2.0.2&dynamic=true&generic=true&interface=person.shw.dubbo.api.DubboApi&lazy=false&methods=getConsumerData&path=person.shw.dubbo.api.DubboApi&pid=3033&protocol=dubbo&qos.enable=false&register=true&register.ip=192.168.31.132&release=2.7.3&remote.application=provider-nacos&side=consumer&sticky=false&timeout=200000&timestamp=1592646265664, dubbo version: 2.7.3, current host: 192.168.31.132
    [泛化调用成功]----->"333333333333333333"
    2020-06-20 17:44:26.409  INFO 3033 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
    2020-06-20 17:44:26.627  INFO 3033 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 10009 (http) with context path ''
    2020-06-20 17:44:26.630  INFO 3033 --- [           main] p.s.dubbo.consumer.DubboConsumerLanuch   : Started DubboConsumerLanuch in 2.383 seconds (JVM running for 2.875)

倒数第四行打印日志，泛化调用成功。

**// TODO 后面补上一个网关gateway使用dubbo泛化调用的例子**

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