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dubbo源码-服务注册(服务端启动源码)

　　在一个微服务的过程中，我们知道一般会有一个注册中心。服务提供者启动之后向注册中心注册自身，服务消费者消费的时候到注册中心拿到注册的服务信息，然后根据服务信息，将请求转发到对应的服务里面，最终通过代理、反射各种方式实现服务的调用。下面简单研究下服务的注册过程以及消费者从服务中心获取到服务之后调用过程。

1. 首先查看服务注册的信息包括：

2. 服务注册过程

1. dubbo-springboot-autoconfigure 包中的spring.factories 配置文件引入了一些自动配置的类

org.springframework.boot.autoconfigure.EnableAutoConfiguration=
org.apache.dubbo.spring.boot.autoconfigure.DubboAutoConfiguration,
org.apache.dubbo.spring.boot.autoconfigure.DubboRelaxedBindingAutoConfiguration
org.springframework.context.ApplicationListener=
org.apache.dubbo.spring.boot.context.event.OverrideDubboConfigApplicationListener,
org.apache.dubbo.spring.boot.context.event.WelcomeLogoApplicationListener,
org.apache.dubbo.spring.boot.context.event.AwaitingNonWebApplicationListener
org.springframework.boot.env.EnvironmentPostProcessor=
org.apache.dubbo.spring.boot.env.DubboDefaultPropertiesEnvironmentPostProcessor
org.springframework.context.ApplicationContextInitializer=
org.apache.dubbo.spring.boot.context.DubboApplicationContextInitializer

2. 其中有个自动配置的类是DubboAutoConfiguration，里面注入了一个重要的bean

package org.apache.dubbo.spring.boot.autoconfigure;

import java.util.Collections;
import java.util.Set;
import org.apache.dubbo.config.spring.beans.factory.annotation.ReferenceAnnotationBeanPostProcessor;
import org.apache.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor;
import org.apache.dubbo.config.spring.context.annotation.DubboConfigConfiguration.Multiple;
import org.apache.dubbo.config.spring.context.annotation.DubboConfigConfiguration.Single;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.Primary;
import org.springframework.core.env.Environment;
import org.springframework.core.env.PropertyResolver;

@ConditionalOnProperty(
    prefix = "dubbo",
    name = {"enabled"},
    matchIfMissing = true
)
@Configuration
@AutoConfigureAfter({DubboRelaxedBindingAutoConfiguration.class})
@EnableConfigurationProperties({DubboConfigurationProperties.class})
public class DubboAutoConfiguration {
    public DubboAutoConfiguration() {
    }

    @ConditionalOnProperty(
        prefix = "dubbo.scan.",
        name = {"base-packages"}
    )
    @ConditionalOnBean(
        name = {"dubboScanBasePackagesPropertyResolver"}
    )
    @Bean
    public ServiceAnnotationBeanPostProcessor serviceAnnotationBeanPostProcessor(@Qualifier("dubboScanBasePackagesPropertyResolver") PropertyResolver propertyResolver) {
        Set<String> packagesToScan = (Set)propertyResolver.getProperty("base-packages", Set.class, Collections.emptySet());
        return new ServiceAnnotationBeanPostProcessor(packagesToScan);
    }

    @ConditionalOnMissingBean
    @Bean(
        name = {"referenceAnnotationBeanPostProcessor"}
    )
    public ReferenceAnnotationBeanPostProcessor referenceAnnotationBeanPostProcessor() {
        return new ReferenceAnnotationBeanPostProcessor();
    }

    @Bean
    @Primary
    public PropertyResolver primaryPropertyResolver(Environment environment) {
        return environment;
    }

    @ConditionalOnProperty(
        prefix = "dubbo.config.",
        name = {"multiple"},
        matchIfMissing = true
    )
    @Import({Multiple.class})
    protected static class MultipleDubboConfigConfiguration {
        protected MultipleDubboConfigConfiguration() {
        }
    }

    @Import({Single.class})
    protected static class SingleDubboConfigConfiguration {
        protected SingleDubboConfigConfiguration() {
        }
    }
}

3. ServiceAnnotationBeanPostProcessor 是重要的入口

(1) ServiceAnnotationBeanPostProcessor 实现了BeanDefinitionRegistryPostProcessor，是一个对象工厂后置处理器

  1 /*
  2  * Licensed to the Apache Software Foundation (ASF) under one or more
  3  * contributor license agreements.  See the NOTICE file distributed with
  4  * this work for additional information regarding copyright ownership.
  5  * The ASF licenses this file to You under the Apache License, Version 2.0
  6  * (the "License"); you may not use this file except in compliance with
  7  * the License.  You may obtain a copy of the License at
  8  *
  9  *     http://www.apache.org/licenses/LICENSE-2.0
 10  *
 11  * Unless required by applicable law or agreed to in writing, software
 12  * distributed under the License is distributed on an "AS IS" BASIS,
 13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  * See the License for the specific language governing permissions and
 15  * limitations under the License.
 16  */
 17 package org.apache.dubbo.config.spring.beans.factory.annotation;
 18 
 19 import org.apache.dubbo.common.logger.Logger;
 20 import org.apache.dubbo.common.logger.LoggerFactory;
 21 import org.apache.dubbo.common.utils.ArrayUtils;
 22 import org.apache.dubbo.config.annotation.Service;
 23 import org.apache.dubbo.config.spring.ServiceBean;
 24 import org.apache.dubbo.config.spring.context.annotation.DubboClassPathBeanDefinitionScanner;
 25 
 26 import org.springframework.beans.BeansException;
 27 import org.springframework.beans.MutablePropertyValues;
 28 import org.springframework.beans.factory.BeanClassLoaderAware;
 29 import org.springframework.beans.factory.config.BeanDefinition;
 30 import org.springframework.beans.factory.config.BeanDefinitionHolder;
 31 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 32 import org.springframework.beans.factory.config.RuntimeBeanReference;
 33 import org.springframework.beans.factory.config.SingletonBeanRegistry;
 34 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 35 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 36 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 37 import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor;
 38 import org.springframework.beans.factory.support.BeanNameGenerator;
 39 import org.springframework.beans.factory.support.ManagedList;
 40 import org.springframework.context.EnvironmentAware;
 41 import org.springframework.context.ResourceLoaderAware;
 42 import org.springframework.context.annotation.AnnotationBeanNameGenerator;
 43 import org.springframework.context.annotation.AnnotationConfigUtils;
 44 import org.springframework.context.annotation.ClassPathBeanDefinitionScanner;
 45 import org.springframework.context.annotation.ConfigurationClassPostProcessor;
 46 import org.springframework.core.annotation.AnnotationAttributes;
 47 import org.springframework.core.env.Environment;
 48 import org.springframework.core.io.ResourceLoader;
 49 import org.springframework.core.type.filter.AnnotationTypeFilter;
 50 import org.springframework.util.CollectionUtils;
 51 import org.springframework.util.ObjectUtils;
 52 import org.springframework.util.StringUtils;
 53 
 54 import java.lang.annotation.Annotation;
 55 import java.util.Arrays;
 56 import java.util.Collection;
 57 import java.util.HashMap;
 58 import java.util.LinkedHashSet;
 59 import java.util.List;
 60 import java.util.Map;
 61 import java.util.Set;
 62 
 63 import static org.apache.dubbo.config.spring.beans.factory.annotation.ServiceBeanNameBuilder.create;
 64 import static org.apache.dubbo.config.spring.util.AnnotationUtils.resolveServiceInterfaceClass;
 65 import static org.apache.dubbo.config.spring.util.ObjectUtils.of;
 66 import static org.springframework.beans.factory.support.BeanDefinitionBuilder.rootBeanDefinition;
 67 import static org.springframework.context.annotation.AnnotationConfigUtils.CONFIGURATION_BEAN_NAME_GENERATOR;
 68 import static org.springframework.core.annotation.AnnotatedElementUtils.findMergedAnnotation;
 69 import static org.springframework.core.annotation.AnnotationUtils.getAnnotationAttributes;
 70 import static org.springframework.util.ClassUtils.resolveClassName;
 71 
 72 /**
 73  * {@link Service} Annotation
 74  * {@link BeanDefinitionRegistryPostProcessor Bean Definition Registry Post Processor}
 75  *
 76  * @since 2.5.8
 77  */
 78 public class ServiceAnnotationBeanPostProcessor implements BeanDefinitionRegistryPostProcessor, EnvironmentAware,
 79         ResourceLoaderAware, BeanClassLoaderAware {
 80 
 81 
 82     private final Logger logger = LoggerFactory.getLogger(getClass());
 83 
 84     private final Set<String> packagesToScan;
 85 
 86     private Environment environment;
 87 
 88     private ResourceLoader resourceLoader;
 89 
 90     private ClassLoader classLoader;
 91 
 92     public ServiceAnnotationBeanPostProcessor(String... packagesToScan) {
 93         this(Arrays.asList(packagesToScan));
 94     }
 95 
 96     public ServiceAnnotationBeanPostProcessor(Collection<String> packagesToScan) {
 97         this(new LinkedHashSet<>(packagesToScan));
 98     }
 99 
100     public ServiceAnnotationBeanPostProcessor(Set<String> packagesToScan) {
101         this.packagesToScan = packagesToScan;
102     }
103 
104     @Override
105     public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
106 
107         Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);
108 
109         if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
110             registerServiceBeans(resolvedPackagesToScan, registry);
111         } else {
112             if (logger.isWarnEnabled()) {
113                 logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
114             }
115         }
116 
117     }
118 
119 
120     /**
121      * Registers Beans whose classes was annotated {@link Service}
122      *
123      * @param packagesToScan The base packages to scan
124      * @param registry       {@link BeanDefinitionRegistry}
125      */
126     private void registerServiceBeans(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
127 
128         DubboClassPathBeanDefinitionScanner scanner =
129                 new DubboClassPathBeanDefinitionScanner(registry, environment, resourceLoader);
130 
131         BeanNameGenerator beanNameGenerator = resolveBeanNameGenerator(registry);
132 
133         scanner.setBeanNameGenerator(beanNameGenerator);
134 
135         scanner.addIncludeFilter(new AnnotationTypeFilter(Service.class));
136 
137         /**
138          * Add the compatibility for legacy Dubbo's @Service
139          *
140          * The issue : https://github.com/apache/dubbo/issues/4330
141          * @since 2.7.3
142          */
143         scanner.addIncludeFilter(new AnnotationTypeFilter(com.alibaba.dubbo.config.annotation.Service.class));
144 
145         for (String packageToScan : packagesToScan) {
146 
147             // Registers @Service Bean first
148             scanner.scan(packageToScan);
149 
150             // Finds all BeanDefinitionHolders of @Service whether @ComponentScan scans or not.
151             Set<BeanDefinitionHolder> beanDefinitionHolders =
152                     findServiceBeanDefinitionHolders(scanner, packageToScan, registry, beanNameGenerator);
153 
154             if (!CollectionUtils.isEmpty(beanDefinitionHolders)) {
155 
156                 for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
157                     registerServiceBean(beanDefinitionHolder, registry, scanner);
158                 }
159 
160                 if (logger.isInfoEnabled()) {
161                     logger.info(beanDefinitionHolders.size() + " annotated Dubbo's @Service Components { " +
162                             beanDefinitionHolders +
163                             " } were scanned under package[" + packageToScan + "]");
164                 }
165 
166             } else {
167 
168                 if (logger.isWarnEnabled()) {
169                     logger.warn("No Spring Bean annotating Dubbo's @Service was found under package["
170                             + packageToScan + "]");
171                 }
172 
173             }
174 
175         }
176 
177     }
178 
179     /**
180      * It'd better to use BeanNameGenerator instance that should reference
181      * {@link ConfigurationClassPostProcessor#componentScanBeanNameGenerator},
182      * thus it maybe a potential problem on bean name generation.
183      *
184      * @param registry {@link BeanDefinitionRegistry}
185      * @return {@link BeanNameGenerator} instance
186      * @see SingletonBeanRegistry
187      * @see AnnotationConfigUtils#CONFIGURATION_BEAN_NAME_GENERATOR
188      * @see ConfigurationClassPostProcessor#processConfigBeanDefinitions
189      * @since 2.5.8
190      */
191     private BeanNameGenerator resolveBeanNameGenerator(BeanDefinitionRegistry registry) {
192 
193         BeanNameGenerator beanNameGenerator = null;
194 
195         if (registry instanceof SingletonBeanRegistry) {
196             SingletonBeanRegistry singletonBeanRegistry = SingletonBeanRegistry.class.cast(registry);
197             beanNameGenerator = (BeanNameGenerator) singletonBeanRegistry.getSingleton(CONFIGURATION_BEAN_NAME_GENERATOR);
198         }
199 
200         if (beanNameGenerator == null) {
201 
202             if (logger.isInfoEnabled()) {
203 
204                 logger.info("BeanNameGenerator bean can't be found in BeanFactory with name ["
205                         + CONFIGURATION_BEAN_NAME_GENERATOR + "]");
206                 logger.info("BeanNameGenerator will be a instance of " +
207                         AnnotationBeanNameGenerator.class.getName() +
208                         " , it maybe a potential problem on bean name generation.");
209             }
210 
211             beanNameGenerator = new AnnotationBeanNameGenerator();
212 
213         }
214 
215         return beanNameGenerator;
216 
217     }
218 
219     /**
220      * Finds a {@link Set} of {@link BeanDefinitionHolder BeanDefinitionHolders} whose bean type annotated
221      * {@link Service} Annotation.
222      *
223      * @param scanner       {@link ClassPathBeanDefinitionScanner}
224      * @param packageToScan pachage to scan
225      * @param registry      {@link BeanDefinitionRegistry}
226      * @return non-null
227      * @since 2.5.8
228      */
229     private Set<BeanDefinitionHolder> findServiceBeanDefinitionHolders(
230             ClassPathBeanDefinitionScanner scanner, String packageToScan, BeanDefinitionRegistry registry,
231             BeanNameGenerator beanNameGenerator) {
232 
233         Set<BeanDefinition> beanDefinitions = scanner.findCandidateComponents(packageToScan);
234 
235         Set<BeanDefinitionHolder> beanDefinitionHolders = new LinkedHashSet<>(beanDefinitions.size());
236 
237         for (BeanDefinition beanDefinition : beanDefinitions) {
238 
239             String beanName = beanNameGenerator.generateBeanName(beanDefinition, registry);
240             BeanDefinitionHolder beanDefinitionHolder = new BeanDefinitionHolder(beanDefinition, beanName);
241             beanDefinitionHolders.add(beanDefinitionHolder);
242 
243         }
244 
245         return beanDefinitionHolders;
246 
247     }
248 
249     /**
250      * Registers {@link ServiceBean} from new annotated {@link Service} {@link BeanDefinition}
251      *
252      * @param beanDefinitionHolder
253      * @param registry
254      * @param scanner
255      * @see ServiceBean
256      * @see BeanDefinition
257      */
258     private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry,
259                                      DubboClassPathBeanDefinitionScanner scanner) {
260 
261         Class<?> beanClass = resolveClass(beanDefinitionHolder);
262 
263         Annotation service = findServiceAnnotation(beanClass);
264 
265         /**
266          * The {@link AnnotationAttributes} of @Service annotation
267          */
268         AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false);
269 
270         Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass);
271 
272         String annotatedServiceBeanName = beanDefinitionHolder.getBeanName();
273 
274         AbstractBeanDefinition serviceBeanDefinition =
275                 buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName);
276 
277         // ServiceBean Bean name
278         String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass);
279 
280         if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean
281             registry.registerBeanDefinition(beanName, serviceBeanDefinition);
282 
283             if (logger.isInfoEnabled()) {
284                 logger.info("The BeanDefinition[" + serviceBeanDefinition +
285                         "] of ServiceBean has been registered with name : " + beanName);
286             }
287 
288         } else {
289 
290             if (logger.isWarnEnabled()) {
291                 logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition +
292                         "] of ServiceBean[ bean name : " + beanName +
293                         "] was be found , Did @DubboComponentScan scan to same package in many times?");
294             }
295 
296         }
297 
298     }
299 
300 
301     /**
302      * Find the {@link Annotation annotation} of @Service
303      *
304      * @param beanClass the {@link Class class} of Bean
305      * @return <code>null</code> if not found
306      * @since 2.7.3
307      */
308     private Annotation findServiceAnnotation(Class<?> beanClass) {
309         Annotation service = findMergedAnnotation(beanClass, Service.class);
310         if (service == null) {
311             service = findMergedAnnotation(beanClass, com.alibaba.dubbo.config.annotation.Service.class);
312         }
313         return service;
314     }
315 
316     /**
317      * Generates the bean name of {@link ServiceBean}
318      *
319      * @param serviceAnnotationAttributes
320      * @param interfaceClass              the class of interface annotated {@link Service}
321      * @return ServiceBean@interfaceClassName#annotatedServiceBeanName
322      * @since 2.7.3
323      */
324     private String generateServiceBeanName(AnnotationAttributes serviceAnnotationAttributes, Class<?> interfaceClass) {
325         ServiceBeanNameBuilder builder = create(interfaceClass, environment)
326                 .group(serviceAnnotationAttributes.getString("group"))
327                 .version(serviceAnnotationAttributes.getString("version"));
328         return builder.build();
329     }
330 
331     private Class<?> resolveClass(BeanDefinitionHolder beanDefinitionHolder) {
332 
333         BeanDefinition beanDefinition = beanDefinitionHolder.getBeanDefinition();
334 
335         return resolveClass(beanDefinition);
336 
337     }
338 
339     private Class<?> resolveClass(BeanDefinition beanDefinition) {
340 
341         String beanClassName = beanDefinition.getBeanClassName();
342 
343         return resolveClassName(beanClassName, classLoader);
344 
345     }
346 
347     private Set<String> resolvePackagesToScan(Set<String> packagesToScan) {
348         Set<String> resolvedPackagesToScan = new LinkedHashSet<String>(packagesToScan.size());
349         for (String packageToScan : packagesToScan) {
350             if (StringUtils.hasText(packageToScan)) {
351                 String resolvedPackageToScan = environment.resolvePlaceholders(packageToScan.trim());
352                 resolvedPackagesToScan.add(resolvedPackageToScan);
353             }
354         }
355         return resolvedPackagesToScan;
356     }
357 
358     /**
359      * Build the {@link AbstractBeanDefinition Bean Definition}
360      *
361      * @param serviceAnnotation
362      * @param serviceAnnotationAttributes
363      * @param interfaceClass
364      * @param annotatedServiceBeanName
365      * @return
366      * @since 2.7.3
367      */
368     private AbstractBeanDefinition buildServiceBeanDefinition(Annotation serviceAnnotation,
369                                                               AnnotationAttributes serviceAnnotationAttributes,
370                                                               Class<?> interfaceClass,
371                                                               String annotatedServiceBeanName) {
372 
373         BeanDefinitionBuilder builder = rootBeanDefinition(ServiceBean.class);
374 
375         AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
376 
377         MutablePropertyValues propertyValues = beanDefinition.getPropertyValues();
378 
379         String[] ignoreAttributeNames = of("provider", "monitor", "application", "module", "registry", "protocol",
380                 "interface", "interfaceName", "parameters");
381 
382         propertyValues.addPropertyValues(new AnnotationPropertyValuesAdapter(serviceAnnotation, environment, ignoreAttributeNames));
383 
384         // References "ref" property to annotated-@Service Bean
385         addPropertyReference(builder, "ref", annotatedServiceBeanName);
386         // Set interface
387         builder.addPropertyValue("interface", interfaceClass.getName());
388         // Convert parameters into map
389         builder.addPropertyValue("parameters", convertParameters(serviceAnnotationAttributes.getStringArray("parameters")));
390 
391         /**
392          * Add {@link org.apache.dubbo.config.ProviderConfig} Bean reference
393          */
394         String providerConfigBeanName = serviceAnnotationAttributes.getString("provider");
395         if (StringUtils.hasText(providerConfigBeanName)) {
396             addPropertyReference(builder, "provider", providerConfigBeanName);
397         }
398 
399         /**
400          * Add {@link org.apache.dubbo.config.MonitorConfig} Bean reference
401          */
402         String monitorConfigBeanName = serviceAnnotationAttributes.getString("monitor");
403         if (StringUtils.hasText(monitorConfigBeanName)) {
404             addPropertyReference(builder, "monitor", monitorConfigBeanName);
405         }
406 
407         /**
408          * Add {@link org.apache.dubbo.config.ApplicationConfig} Bean reference
409          */
410         String applicationConfigBeanName = serviceAnnotationAttributes.getString("application");
411         if (StringUtils.hasText(applicationConfigBeanName)) {
412             addPropertyReference(builder, "application", applicationConfigBeanName);
413         }
414 
415         /**
416          * Add {@link org.apache.dubbo.config.ModuleConfig} Bean reference
417          */
418         String moduleConfigBeanName = serviceAnnotationAttributes.getString("module");
419         if (StringUtils.hasText(moduleConfigBeanName)) {
420             addPropertyReference(builder, "module", moduleConfigBeanName);
421         }
422 
423 
424         /**
425          * Add {@link org.apache.dubbo.config.RegistryConfig} Bean reference
426          */
427         String[] registryConfigBeanNames = serviceAnnotationAttributes.getStringArray("registry");
428 
429         List<RuntimeBeanReference> registryRuntimeBeanReferences = toRuntimeBeanReferences(registryConfigBeanNames);
430 
431         if (!registryRuntimeBeanReferences.isEmpty()) {
432             builder.addPropertyValue("registries", registryRuntimeBeanReferences);
433         }
434 
435         /**
436          * Add {@link org.apache.dubbo.config.ProtocolConfig} Bean reference
437          */
438         String[] protocolConfigBeanNames = serviceAnnotationAttributes.getStringArray("protocol");
439 
440         List<RuntimeBeanReference> protocolRuntimeBeanReferences = toRuntimeBeanReferences(protocolConfigBeanNames);
441 
442         if (!protocolRuntimeBeanReferences.isEmpty()) {
443             builder.addPropertyValue("protocols", protocolRuntimeBeanReferences);
444         }
445 
446         return builder.getBeanDefinition();
447 
448     }
449 
450 
451     private ManagedList<RuntimeBeanReference> toRuntimeBeanReferences(String... beanNames) {
452 
453         ManagedList<RuntimeBeanReference> runtimeBeanReferences = new ManagedList<>();
454 
455         if (!ObjectUtils.isEmpty(beanNames)) {
456 
457             for (String beanName : beanNames) {
458 
459                 String resolvedBeanName = environment.resolvePlaceholders(beanName);
460 
461                 runtimeBeanReferences.add(new RuntimeBeanReference(resolvedBeanName));
462             }
463 
464         }
465 
466         return runtimeBeanReferences;
467 
468     }
469 
470     private void addPropertyReference(BeanDefinitionBuilder builder, String propertyName, String beanName) {
471         String resolvedBeanName = environment.resolvePlaceholders(beanName);
472         builder.addPropertyReference(propertyName, resolvedBeanName);
473     }
474 
475 
476     private Map<String, String> convertParameters(String[] parameters) {
477         if (ArrayUtils.isEmpty(parameters)) {
478             return null;
479         }
480 
481         if (parameters.length % 2 != 0) {
482             throw new IllegalArgumentException("parameter attribute must be paired with key followed by value");
483         }
484 
485         Map<String, String> map = new HashMap<>();
486         for (int i = 0; i < parameters.length; i += 2) {
487             map.put(parameters[i], parameters[i + 1]);
488         }
489         return map;
490     }
491 
492     @Override
493     public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
494 
495     }
496 
497     @Override
498     public void setEnvironment(Environment environment) {
499         this.environment = environment;
500     }
501 
502     @Override
503     public void setResourceLoader(ResourceLoader resourceLoader) {
504         this.resourceLoader = resourceLoader;
505     }
506 
507     @Override
508     public void setBeanClassLoader(ClassLoader classLoader) {
509         this.classLoader = classLoader;
510     }
511 
512 }

View Code

(2) org.apache.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor#postProcessBeanDefinitionRegistry 是程序入口，如果配置了dubbo 扫描的包，会扫描包进行注册到Spring 中，调用方法 org.apache.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor#registerServiceBeans ，所以该方法是核心

1》registerServiceBeans方法内部满足Spring 的设计思路，先根据注解拿到classpath 中带指定注解的类，如下拿的是apache包下的Service.class 和 alibaba 包下的Service 注解

        scanner.addIncludeFilter(new AnnotationTypeFilter(Service.class));

        scanner.addIncludeFilter(new AnnotationTypeFilter(com.alibaba.dubbo.config.annotation.Service.class));

2》调用scanner.scan(packageToScan); 先注册Service 注解声明的对象到Spring 容器

3》调用方法 org.apache.dubbo.config.spring.beans.factory.annotation.ServiceAnnotationBeanPostProcessor#findServiceBeanDefinitionHolders 生成BeanDefinition (所有带@Service 注解的类)

该方法内部先生成beanName，然后创建BeanDefinitionHolder

4》registerServiceBean 方法为每个Service 类注册一个ServiceBean 对象。

这个方法的逻辑是：获取Service上的属性-》调用buildServiceBeanDefinition 生成一个抽象BeanDefinition 对象，包含一些基本的属性 -》生成beanName -》注册到Spring 中

　　到这里完成了Spring beandefinition 的注入过程，接下来SpringIOC进入创建对象以及后续的启动流程。这里注意 buildServiceBeanDefinition 有个重要的过程就是通过下面方法设置属性：addPropertyReference(builder, "ref", annotatedServiceBeanName);，这其实就是将ref 属性设为前面解析的service的beanName。(通过org.springframework.beans.factory.support.BeanDefinitionBuilder#addPropertyReference 方式添加的属性，spring 会在创建对象的过程中属性注入过程populateBean 方法中自动注入)

4. ServiceBean 启动过程

(1) ServiceBean 实现了ApplicationListener<ContextRefreshedEvent> 接口，在Spring创建完单例对象之后会进行事件发布

  1 /*
  2  * Licensed to the Apache Software Foundation (ASF) under one or more
  3  * contributor license agreements.  See the NOTICE file distributed with
  4  * this work for additional information regarding copyright ownership.
  5  * The ASF licenses this file to You under the Apache License, Version 2.0
  6  * (the "License"); you may not use this file except in compliance with
  7  * the License.  You may obtain a copy of the License at
  8  *
  9  *     http://www.apache.org/licenses/LICENSE-2.0
 10  *
 11  * Unless required by applicable law or agreed to in writing, software
 12  * distributed under the License is distributed on an "AS IS" BASIS,
 13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  * See the License for the specific language governing permissions and
 15  * limitations under the License.
 16  */
 17 package org.apache.dubbo.config.spring;
 18 
 19 import org.apache.dubbo.common.utils.CollectionUtils;
 20 import org.apache.dubbo.common.utils.StringUtils;
 21 import org.apache.dubbo.config.ApplicationConfig;
 22 import org.apache.dubbo.config.ConfigCenterConfig;
 23 import org.apache.dubbo.config.MetadataReportConfig;
 24 import org.apache.dubbo.config.MetricsConfig;
 25 import org.apache.dubbo.config.ModuleConfig;
 26 import org.apache.dubbo.config.MonitorConfig;
 27 import org.apache.dubbo.config.ProtocolConfig;
 28 import org.apache.dubbo.config.ProviderConfig;
 29 import org.apache.dubbo.config.RegistryConfig;
 30 import org.apache.dubbo.config.ServiceConfig;
 31 import org.apache.dubbo.config.annotation.Service;
 32 import org.apache.dubbo.config.spring.context.event.ServiceBeanExportedEvent;
 33 import org.apache.dubbo.config.spring.extension.SpringExtensionFactory;
 34 
 35 import org.springframework.aop.support.AopUtils;
 36 import org.springframework.beans.factory.BeanFactoryUtils;
 37 import org.springframework.beans.factory.BeanNameAware;
 38 import org.springframework.beans.factory.DisposableBean;
 39 import org.springframework.beans.factory.InitializingBean;
 40 import org.springframework.context.ApplicationContext;
 41 import org.springframework.context.ApplicationContextAware;
 42 import org.springframework.context.ApplicationEventPublisher;
 43 import org.springframework.context.ApplicationEventPublisherAware;
 44 import org.springframework.context.ApplicationListener;
 45 import org.springframework.context.event.ContextRefreshedEvent;
 46 
 47 import java.util.ArrayList;
 48 import java.util.Arrays;
 49 import java.util.List;
 50 import java.util.Map;
 51 
 52 import static org.apache.dubbo.common.constants.CommonConstants.COMMA_SPLIT_PATTERN;
 53 import static org.apache.dubbo.config.spring.util.BeanFactoryUtils.addApplicationListener;
 54 
 55 /**
 56  * ServiceFactoryBean
 57  *
 58  * @export
 59  */
 60 public class ServiceBean<T> extends ServiceConfig<T> implements InitializingBean, DisposableBean,
 61         ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware,
 62         ApplicationEventPublisherAware {
 63 
 64 
 65     private static final long serialVersionUID = 213195494150089726L;
 66 
 67     private final transient Service service;
 68 
 69     private transient ApplicationContext applicationContext;
 70 
 71     private transient String beanName;
 72 
 73     private transient boolean supportedApplicationListener;
 74 
 75     private ApplicationEventPublisher applicationEventPublisher;
 76 
 77     public ServiceBean() {
 78         super();
 79         this.service = null;
 80     }
 81 
 82     public ServiceBean(Service service) {
 83         super(service);
 84         this.service = service;
 85     }
 86 
 87     @Override
 88     public void setApplicationContext(ApplicationContext applicationContext) {
 89         this.applicationContext = applicationContext;
 90         SpringExtensionFactory.addApplicationContext(applicationContext);
 91         supportedApplicationListener = addApplicationListener(applicationContext, this);
 92     }
 93 
 94     @Override
 95     public void setBeanName(String name) {
 96         this.beanName = name;
 97     }
 98 
 99     /**
100      * Gets associated {@link Service}
101      *
102      * @return associated {@link Service}
103      */
104     public Service getService() {
105         return service;
106     }
107 
108     @Override
109     public void onApplicationEvent(ContextRefreshedEvent event) {
110         if (!isExported() && !isUnexported()) {
111             if (logger.isInfoEnabled()) {
112                 logger.info("The service ready on spring started. service: " + getInterface());
113             }
114             export();
115         }
116     }
117 
118     @Override
119     @SuppressWarnings({"unchecked", "deprecation"})
120     public void afterPropertiesSet() throws Exception {
121         if (getProvider() == null) {
122             Map<String, ProviderConfig> providerConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProviderConfig.class, false, false);
123             if (providerConfigMap != null && providerConfigMap.size() > 0) {
124                 Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
125                 if (CollectionUtils.isEmptyMap(protocolConfigMap)
126                         && providerConfigMap.size() > 1) { // backward compatibility
127                     List<ProviderConfig> providerConfigs = new ArrayList<ProviderConfig>();
128                     for (ProviderConfig config : providerConfigMap.values()) {
129                         if (config.isDefault() != null && config.isDefault()) {
130                             providerConfigs.add(config);
131                         }
132                     }
133                     if (!providerConfigs.isEmpty()) {
134                         setProviders(providerConfigs);
135                     }
136                 } else {
137                     ProviderConfig providerConfig = null;
138                     for (ProviderConfig config : providerConfigMap.values()) {
139                         if (config.isDefault() == null || config.isDefault()) {
140                             if (providerConfig != null) {
141                                 throw new IllegalStateException("Duplicate provider configs: " + providerConfig + " and " + config);
142                             }
143                             providerConfig = config;
144                         }
145                     }
146                     if (providerConfig != null) {
147                         setProvider(providerConfig);
148                     }
149                 }
150             }
151         }
152         if (getApplication() == null
153                 && (getProvider() == null || getProvider().getApplication() == null)) {
154             Map<String, ApplicationConfig> applicationConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ApplicationConfig.class, false, false);
155             if (applicationConfigMap != null && applicationConfigMap.size() > 0) {
156                 ApplicationConfig applicationConfig = null;
157                 for (ApplicationConfig config : applicationConfigMap.values()) {
158                     if (applicationConfig != null) {
159                         throw new IllegalStateException("Duplicate application configs: " + applicationConfig + " and " + config);
160                     }
161                     applicationConfig = config;
162                 }
163                 if (applicationConfig != null) {
164                     setApplication(applicationConfig);
165                 }
166             }
167         }
168         if (getModule() == null
169                 && (getProvider() == null || getProvider().getModule() == null)) {
170             Map<String, ModuleConfig> moduleConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ModuleConfig.class, false, false);
171             if (moduleConfigMap != null && moduleConfigMap.size() > 0) {
172                 ModuleConfig moduleConfig = null;
173                 for (ModuleConfig config : moduleConfigMap.values()) {
174                     if (config.isDefault() == null || config.isDefault()) {
175                         if (moduleConfig != null) {
176                             throw new IllegalStateException("Duplicate module configs: " + moduleConfig + " and " + config);
177                         }
178                         moduleConfig = config;
179                     }
180                 }
181                 if (moduleConfig != null) {
182                     setModule(moduleConfig);
183                 }
184             }
185         }
186 
187         if (StringUtils.isEmpty(getRegistryIds())) {
188             if (getApplication() != null && StringUtils.isNotEmpty(getApplication().getRegistryIds())) {
189                 setRegistryIds(getApplication().getRegistryIds());
190             }
191             if (getProvider() != null && StringUtils.isNotEmpty(getProvider().getRegistryIds())) {
192                 setRegistryIds(getProvider().getRegistryIds());
193             }
194         }
195 
196         if ((CollectionUtils.isEmpty(getRegistries()))
197                 && (getProvider() == null || CollectionUtils.isEmpty(getProvider().getRegistries()))
198                 && (getApplication() == null || CollectionUtils.isEmpty(getApplication().getRegistries()))) {
199             Map<String, RegistryConfig> registryConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, RegistryConfig.class, false, false);
200             if (CollectionUtils.isNotEmptyMap(registryConfigMap)) {
201                 List<RegistryConfig> registryConfigs = new ArrayList<>();
202                 if (StringUtils.isNotEmpty(registryIds)) {
203                     Arrays.stream(COMMA_SPLIT_PATTERN.split(registryIds)).forEach(id -> {
204                         if (registryConfigMap.containsKey(id)) {
205                             registryConfigs.add(registryConfigMap.get(id));
206                         }
207                     });
208                 }
209 
210                 if (registryConfigs.isEmpty()) {
211                     for (RegistryConfig config : registryConfigMap.values()) {
212                         if (StringUtils.isEmpty(registryIds)) {
213                             registryConfigs.add(config);
214                         }
215                     }
216                 }
217                 if (!registryConfigs.isEmpty()) {
218                     super.setRegistries(registryConfigs);
219                 }
220             }
221         }
222         if (getMetadataReportConfig() == null) {
223             Map<String, MetadataReportConfig> metadataReportConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MetadataReportConfig.class, false, false);
224             if (metadataReportConfigMap != null && metadataReportConfigMap.size() == 1) {
225                 super.setMetadataReportConfig(metadataReportConfigMap.values().iterator().next());
226             } else if (metadataReportConfigMap != null && metadataReportConfigMap.size() > 1) {
227                 throw new IllegalStateException("Multiple MetadataReport configs: " + metadataReportConfigMap);
228             }
229         }
230 
231         if (getConfigCenter() == null) {
232             Map<String, ConfigCenterConfig> configenterMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ConfigCenterConfig.class, false, false);
233             if (configenterMap != null && configenterMap.size() == 1) {
234                 super.setConfigCenter(configenterMap.values().iterator().next());
235             } else if (configenterMap != null && configenterMap.size() > 1) {
236                 throw new IllegalStateException("Multiple ConfigCenter found:" + configenterMap);
237             }
238         }
239 
240         if (getMonitor() == null
241                 && (getProvider() == null || getProvider().getMonitor() == null)
242                 && (getApplication() == null || getApplication().getMonitor() == null)) {
243             Map<String, MonitorConfig> monitorConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MonitorConfig.class, false, false);
244             if (monitorConfigMap != null && monitorConfigMap.size() > 0) {
245                 MonitorConfig monitorConfig = null;
246                 for (MonitorConfig config : monitorConfigMap.values()) {
247                     if (config.isDefault() == null || config.isDefault()) {
248                         if (monitorConfig != null) {
249                             throw new IllegalStateException("Duplicate monitor configs: " + monitorConfig + " and " + config);
250                         }
251                         monitorConfig = config;
252                     }
253                 }
254                 if (monitorConfig != null) {
255                     setMonitor(monitorConfig);
256                 }
257             }
258         }
259 
260         if (getMetrics() == null) {
261             Map<String, MetricsConfig> metricsConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, MetricsConfig.class, false, false);
262             if (metricsConfigMap != null && metricsConfigMap.size() > 0) {
263                 MetricsConfig metricsConfig = null;
264                 for (MetricsConfig config : metricsConfigMap.values()) {
265                     if (metricsConfig != null) {
266                         throw new IllegalStateException("Duplicate metrics configs: " + metricsConfig + " and " + config);
267                     }
268                     metricsConfig = config;
269                 }
270                 if (metricsConfig != null) {
271                     setMetrics(metricsConfig);
272                 }
273             }
274         }
275 
276         if (StringUtils.isEmpty(getProtocolIds())) {
277             if (getProvider() != null && StringUtils.isNotEmpty(getProvider().getProtocolIds())) {
278                 setProtocolIds(getProvider().getProtocolIds());
279             }
280         }
281 
282         if (CollectionUtils.isEmpty(getProtocols())
283                 && (getProvider() == null || CollectionUtils.isEmpty(getProvider().getProtocols()))) {
284             Map<String, ProtocolConfig> protocolConfigMap = applicationContext == null ? null : BeanFactoryUtils.beansOfTypeIncludingAncestors(applicationContext, ProtocolConfig.class, false, false);
285             if (protocolConfigMap != null && protocolConfigMap.size() > 0) {
286                 List<ProtocolConfig> protocolConfigs = new ArrayList<ProtocolConfig>();
287                 if (StringUtils.isNotEmpty(getProtocolIds())) {
288                     Arrays.stream(COMMA_SPLIT_PATTERN.split(getProtocolIds()))
289                             .forEach(id -> {
290                                 if (protocolConfigMap.containsKey(id)) {
291                                     protocolConfigs.add(protocolConfigMap.get(id));
292                                 }
293                             });
294                 }
295 
296                 if (protocolConfigs.isEmpty()) {
297                     for (ProtocolConfig config : protocolConfigMap.values()) {
298                         if (StringUtils.isEmpty(protocolIds)) {
299                             protocolConfigs.add(config);
300                         }
301                     }
302                 }
303 
304                 if (!protocolConfigs.isEmpty()) {
305                     super.setProtocols(protocolConfigs);
306                 }
307             }
308         }
309         if (StringUtils.isEmpty(getPath())) {
310             if (StringUtils.isNotEmpty(beanName)
311                     && StringUtils.isNotEmpty(getInterface())
312                     && beanName.startsWith(getInterface())) {
313                 setPath(beanName);
314             }
315         }
316         if (!supportedApplicationListener) {
317             export();
318         }
319     }
320 
321     /**
322      * Get the name of {@link ServiceBean}
323      *
324      * @return {@link ServiceBean}'s name
325      * @since 2.6.5
326      */
327     public String getBeanName() {
328         return this.beanName;
329     }
330 
331     /**
332      * @since 2.6.5
333      */
334     @Override
335     public void export() {
336         super.export();
337         // Publish ServiceBeanExportedEvent
338         publishExportEvent();
339     }
340 
341     /**
342      * @since 2.6.5
343      */
344     private void publishExportEvent() {
345         ServiceBeanExportedEvent exportEvent = new ServiceBeanExportedEvent(this);
346         applicationEventPublisher.publishEvent(exportEvent);
347     }
348 
349     @Override
350     public void destroy() throws Exception {
351         // no need to call unexport() here, see
352         // org.apache.dubbo.config.spring.extension.SpringExtensionFactory.ShutdownHookListener
353     }
354 
355     // merged from dubbox
356     @Override
357     protected Class getServiceClass(T ref) {
358         if (AopUtils.isAopProxy(ref)) {
359             return AopUtils.getTargetClass(ref);
360         }
361         return super.getServiceClass(ref);
362     }
363 
364     /**
365      * @param applicationEventPublisher
366      * @since 2.6.5
367      */
368     @Override
369     public void setApplicationEventPublisher(ApplicationEventPublisher applicationEventPublisher) {
370         this.applicationEventPublisher = applicationEventPublisher;
371     }
372 }

View Code

　　事件调用过程如下：org.springframework.context.support.AbstractApplicationContext#finishRefresh 方法内部的publishEvent(new ContextRefreshedEvent(this)); -》org.apache.dubbo.config.spring.ServiceBean#onApplicationEvent 这里的核心逻辑其实也是获取到容器中所有的ApplicationListener 然调用其onApplicationEvent 方法。调用链如下：

(2) org.apache.dubbo.config.spring.ServiceBean#export 方法进行发布服务到注册中心

(3) 调用到org.apache.dubbo.config.ServiceConfig#export

  1     private void doExportUrls() {
  2         List<URL> registryURLs = loadRegistries(true);
  3         for (ProtocolConfig protocolConfig : protocols) {
  4             String pathKey = URL.buildKey(getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), group, version);
  5             ProviderModel providerModel = new ProviderModel(pathKey, ref, interfaceClass);
  6             ApplicationModel.initProviderModel(pathKey, providerModel);
  7             doExportUrlsFor1Protocol(protocolConfig, registryURLs);
  8         }
  9     }
 10 
 11     private void doExportUrlsFor1Protocol(ProtocolConfig protocolConfig, List<URL> registryURLs) {
 12         String name = protocolConfig.getName();
 13         if (StringUtils.isEmpty(name)) {
 14             name = DUBBO;
 15         }
 16 
 17         Map<String, String> map = new HashMap<String, String>();
 18         map.put(SIDE_KEY, PROVIDER_SIDE);
 19 
 20         appendRuntimeParameters(map);
 21         appendParameters(map, metrics);
 22         appendParameters(map, application);
 23         appendParameters(map, module);
 24         // remove 'default.' prefix for configs from ProviderConfig
 25         // appendParameters(map, provider, Constants.DEFAULT_KEY);
 26         appendParameters(map, provider);
 27         appendParameters(map, protocolConfig);
 28         appendParameters(map, this);
 29         if (CollectionUtils.isNotEmpty(methods)) {
 30             for (MethodConfig method : methods) {
 31                 appendParameters(map, method, method.getName());
 32                 String retryKey = method.getName() + ".retry";
 33                 if (map.containsKey(retryKey)) {
 34                     String retryValue = map.remove(retryKey);
 35                     if ("false".equals(retryValue)) {
 36                         map.put(method.getName() + ".retries", "0");
 37                     }
 38                 }
 39                 List<ArgumentConfig> arguments = method.getArguments();
 40                 if (CollectionUtils.isNotEmpty(arguments)) {
 41                     for (ArgumentConfig argument : arguments) {
 42                         // convert argument type
 43                         if (argument.getType() != null && argument.getType().length() > 0) {
 44                             Method[] methods = interfaceClass.getMethods();
 45                             // visit all methods
 46                             if (methods != null && methods.length > 0) {
 47                                 for (int i = 0; i < methods.length; i++) {
 48                                     String methodName = methods[i].getName();
 49                                     // target the method, and get its signature
 50                                     if (methodName.equals(method.getName())) {
 51                                         Class<?>[] argtypes = methods[i].getParameterTypes();
 52                                         // one callback in the method
 53                                         if (argument.getIndex() != -1) {
 54                                             if (argtypes[argument.getIndex()].getName().equals(argument.getType())) {
 55                                                 appendParameters(map, argument, method.getName() + "." + argument.getIndex());
 56                                             } else {
 57                                                 throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
 58                                             }
 59                                         } else {
 60                                             // multiple callbacks in the method
 61                                             for (int j = 0; j < argtypes.length; j++) {
 62                                                 Class<?> argclazz = argtypes[j];
 63                                                 if (argclazz.getName().equals(argument.getType())) {
 64                                                     appendParameters(map, argument, method.getName() + "." + j);
 65                                                     if (argument.getIndex() != -1 && argument.getIndex() != j) {
 66                                                         throw new IllegalArgumentException("Argument config error : the index attribute and type attribute not match :index :" + argument.getIndex() + ", type:" + argument.getType());
 67                                                     }
 68                                                 }
 69                                             }
 70                                         }
 71                                     }
 72                                 }
 73                             }
 74                         } else if (argument.getIndex() != -1) {
 75                             appendParameters(map, argument, method.getName() + "." + argument.getIndex());
 76                         } else {
 77                             throw new IllegalArgumentException("Argument config must set index or type attribute.eg: <dubbo:argument index='0' .../> or <dubbo:argument type=xxx .../>");
 78                         }
 79 
 80                     }
 81                 }
 82             } // end of methods for
 83         }
 84 
 85         if (ProtocolUtils.isGeneric(generic)) {
 86             map.put(GENERIC_KEY, generic);
 87             map.put(METHODS_KEY, ANY_VALUE);
 88         } else {
 89             String revision = Version.getVersion(interfaceClass, version);
 90             if (revision != null && revision.length() > 0) {
 91                 map.put(REVISION_KEY, revision);
 92             }
 93 
 94             String[] methods = Wrapper.getWrapper(interfaceClass).getMethodNames();
 95             if (methods.length == 0) {
 96                 logger.warn("No method found in service interface " + interfaceClass.getName());
 97                 map.put(METHODS_KEY, ANY_VALUE);
 98             } else {
 99                 map.put(METHODS_KEY, StringUtils.join(new HashSet<String>(Arrays.asList(methods)), ","));
100             }
101         }
102         if (!ConfigUtils.isEmpty(token)) {
103             if (ConfigUtils.isDefault(token)) {
104                 map.put(TOKEN_KEY, UUID.randomUUID().toString());
105             } else {
106                 map.put(TOKEN_KEY, token);
107             }
108         }
109         // export service
110         String host = this.findConfigedHosts(protocolConfig, registryURLs, map);
111         Integer port = this.findConfigedPorts(protocolConfig, name, map);
112         URL url = new URL(name, host, port, getContextPath(protocolConfig).map(p -> p + "/" + path).orElse(path), map);
113 
114         if (ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
115                 .hasExtension(url.getProtocol())) {
116             url = ExtensionLoader.getExtensionLoader(ConfiguratorFactory.class)
117                     .getExtension(url.getProtocol()).getConfigurator(url).configure(url);
118         }
119 
120         String scope = url.getParameter(SCOPE_KEY);
121         // don't export when none is configured
122         if (!SCOPE_NONE.equalsIgnoreCase(scope)) {
123 
124             // export to local if the config is not remote (export to remote only when config is remote)
125             if (!SCOPE_REMOTE.equalsIgnoreCase(scope)) {
126                 exportLocal(url);
127             }
128             // export to remote if the config is not local (export to local only when config is local)
129             if (!SCOPE_LOCAL.equalsIgnoreCase(scope)) {
130                 if (!isOnlyInJvm() && logger.isInfoEnabled()) {
131                     logger.info("Export dubbo service " + interfaceClass.getName() + " to url " + url);
132                 }
133                 if (CollectionUtils.isNotEmpty(registryURLs)) {
134                     for (URL registryURL : registryURLs) {
135                         //if protocol is only injvm ,not register
136                         if (LOCAL_PROTOCOL.equalsIgnoreCase(url.getProtocol())) {
137                             continue;
138                         }
139                         url = url.addParameterIfAbsent(DYNAMIC_KEY, registryURL.getParameter(DYNAMIC_KEY));
140                         URL monitorUrl = loadMonitor(registryURL);
141                         if (monitorUrl != null) {
142                             url = url.addParameterAndEncoded(MONITOR_KEY, monitorUrl.toFullString());
143                         }
144                         if (logger.isInfoEnabled()) {
145                             logger.info("Register dubbo service " + interfaceClass.getName() + " url " + url + " to registry " + registryURL);
146                         }
147 
148                         // For providers, this is used to enable custom proxy to generate invoker
149                         String proxy = url.getParameter(PROXY_KEY);
150                         if (StringUtils.isNotEmpty(proxy)) {
151                             registryURL = registryURL.addParameter(PROXY_KEY, proxy);
152                         }
153 
154                         Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
155                         DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
156 
157                         Exporter<?> exporter = protocol.export(wrapperInvoker);
158                         exporters.add(exporter);
159                     }
160                 } else {
161                     Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, url);
162                     DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);
163 
164                     Exporter<?> exporter = protocol.export(wrapperInvoker);
165                     exporters.add(exporter);
166                 }
167                 /**
168                  * @since 2.7.0
169                  * ServiceData Store
170                  */
171                 MetadataReportService metadataReportService = null;
172                 if ((metadataReportService = getMetadataReportService()) != null) {
173                     metadataReportService.publishProvider(url);
174                 }
175             }
176         }
177         this.urls.add(url);
178     }

所以核心注册服务的过程在doExportUrlsFor1Protocol里面进行发布：可以看到这个过程中会多次出现URL，registery 协议以及dubbo 协议，这是dubbo 根据URL选择对应的策略进行操作的设计，可以说URL用于传参以及选择对应的实现类

1》方法调用的时候获取到的registryURLs 如下：

2》12-109 行是解析参数往map 里面塞，然后构造URL对象

3》110 - 112 行解析主机和端口，然后构造发布的url 对象用于发布,构造的URL对象如下：可以看到走得是 dubbo 协议

协议如下：

dubbo://192.168.99.1:20880/cn.qz.dubbo.service.GroupService?anyhost=true&application=dubbp-service-impl&bean.name=ServiceBean:cn.qz.dubbo.service.GroupService:1.0.0&bind.ip=192.168.99.1&bind.port=20880&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=cn.qz.dubbo.service.GroupService&methods=add,listAll&pid=14292&qos.enable=false&register=true&release=2.7.3&revision=1.0.0&side=provider&timestamp=1629273507675&version=1.0.0

4》120行获取的scope 属性为null，所以会走122行的代码块，然后进行服务的发布，服务的发布有两个，一个是发布到JVM内存，一个是发布到注册中心

exportLocal(url); 暴露服务到本地

    /**
     * always export injvm
     */
    private void exportLocal(URL url) {
        URL local = URLBuilder.from(url)
                .setProtocol(LOCAL_PROTOCOL)
                .setHost(LOCALHOST_VALUE)
                .setPort(0)
                .build();
        Exporter<?> exporter = protocol.export(
                PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, local));
        exporters.add(exporter);
        logger.info("Export dubbo service " + interfaceClass.getName() + " to local registry url : " + local);
    }

首先修改协议为injvm 协议：

然后调用org.apache.dubbo.rpc.protocol.injvm.InjvmProtocol#export：

    @Override
    public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        return new InjvmExporter<T>(invoker, invoker.getUrl().getServiceKey(), exporterMap);
    }

然后调用org.apache.dubbo.rpc.protocol.injvm.InjvmExporter#InjvmExporter：

    InjvmExporter(Invoker<T> invoker, String key, Map<String, Exporter<?>> exporterMap) {
        super(invoker);
        this.key = key;
        this.exporterMap = exporterMap;
        exporterMap.put(key, this);
    }

　　获取到的invoker 信息如下：

　　invoker对象如下：

    private static <T> Invoker<T> buildInvokerChain(final Invoker<T> invoker, String key, String group) {
        Invoker<T> last = invoker;
        List<Filter> filters = ExtensionLoader.getExtensionLoader(Filter.class).getActivateExtension(invoker.getUrl(), key, group);

        if (!filters.isEmpty()) {
            for (int i = filters.size() - 1; i >= 0; i--) {
                final Filter filter = filters.get(i);
                final Invoker<T> next = last;
                last = new Invoker<T>() {

                    @Override
                    public Class<T> getInterface() {
                        return invoker.getInterface();
                    }

                    @Override
                    public URL getUrl() {
                        return invoker.getUrl();
                    }

                    @Override
                    public boolean isAvailable() {
                        return invoker.isAvailable();
                    }

                    @Override
                    public Result invoke(Invocation invocation) throws RpcException {
                        Result asyncResult;
                        try {
                            asyncResult = filter.invoke(next, invocation);
                        } catch (Exception e) {
                            // onError callback
                            if (filter instanceof ListenableFilter) {
                                Filter.Listener listener = ((ListenableFilter) filter).listener();
                                if (listener != null) {
                                    listener.onError(e, invoker, invocation);
                                }
                            }
                            throw e;
                        }
                        return asyncResult;
                    }

                    @Override
                    public void destroy() {
                        invoker.destroy();
                    }

                    @Override
                    public String toString() {
                        return invoker.toString();
                    }
                };
            }
        }

        return new CallbackRegistrationInvoker<>(last, filters);
    }

远程暴露服务

下面代码进行远程暴露

                        Invoker<?> invoker = PROXY_FACTORY.getInvoker(ref, (Class) interfaceClass, registryURL.addParameterAndEncoded(EXPORT_KEY, url.toFullString()));
                        DelegateProviderMetaDataInvoker wrapperInvoker = new DelegateProviderMetaDataInvoker(invoker, this);

                        Exporter<?> exporter = protocol.export(wrapperInvoker);
                        exporters.add(exporter);

　　在进行远程暴露前进行了一系列的判断，如果只暴露本地服务就直接退出暴露过程；如果有监控就添加监控信息；然后走上面贴出的暴露代码

构造的invoker 对象如下：

　　url信息如下：

registry://192.168.99.100:2181/org.apache.dubbo.registry.RegistryService?application=dubbp-service-impl&dubbo=2.0.2&export=dubbo%3A%2F%2F192.168.99.1%3A20880%2Fcn.qz.dubbo.service.GroupService%3Fanyhost%3Dtrue%26application%3Ddubbp-service-impl%26bean.name%3DServiceBean%3Acn.qz.dubbo.service.GroupService%3A1.0.0%26bind.ip%3D192.168.99.1%26bind.port%3D20880%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dcn.qz.dubbo.service.GroupService%26methods%3Dadd%2ClistAll%26pid%3D27024%26qos.enable%3Dfalse%26register%3Dtrue%26release%3D2.7.3%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1629276323291%26version%3D1.0.0&pid=27024&qos.enable=false&registry=zookeeper&release=2.7.3&timestamp=1629276323288

接下来进行注册，可以看到协议使用的是registery，因此走：org.apache.dubbo.registry.integration.RegistryProtocol#export

    @Override
    public <T> Exporter<T> export(final Invoker<T> originInvoker) throws RpcException {
        URL registryUrl = getRegistryUrl(originInvoker);
        // url to export locally
        URL providerUrl = getProviderUrl(originInvoker);

        // Subscribe the override data
        // FIXME When the provider subscribes, it will affect the scene : a certain JVM exposes the service and call
        //  the same service. Because the subscribed is cached key with the name of the service, it causes the
        //  subscription information to cover.
        final URL overrideSubscribeUrl = getSubscribedOverrideUrl(providerUrl);
        final OverrideListener overrideSubscribeListener = new OverrideListener(overrideSubscribeUrl, originInvoker);
        overrideListeners.put(overrideSubscribeUrl, overrideSubscribeListener);

        providerUrl = overrideUrlWithConfig(providerUrl, overrideSubscribeListener);
        //export invoker
        final ExporterChangeableWrapper<T> exporter = doLocalExport(originInvoker, providerUrl);

        // url to registry
        final Registry registry = getRegistry(originInvoker);
        final URL registeredProviderUrl = getRegisteredProviderUrl(providerUrl, registryUrl);
        ProviderInvokerWrapper<T> providerInvokerWrapper = ProviderConsumerRegTable.registerProvider(originInvoker,
                registryUrl, registeredProviderUrl);
        //to judge if we need to delay publish
        boolean register = registeredProviderUrl.getParameter("register", true);
        if (register) {
            register(registryUrl, registeredProviderUrl);
            providerInvokerWrapper.setReg(true);
        }

        // Deprecated! Subscribe to override rules in 2.6.x or before.
        registry.subscribe(overrideSubscribeUrl, overrideSubscribeListener);

        exporter.setRegisterUrl(registeredProviderUrl);
        exporter.setSubscribeUrl(overrideSubscribeUrl);
        //Ensure that a new exporter instance is returned every time export
        return new DestroyableExporter<>(exporter);
    }

然后调用org.apache.dubbo.registry.integration.RegistryProtocol#register 进行注册：

    public void register(URL registryUrl, URL registeredProviderUrl) {
        Registry registry = registryFactory.getRegistry(registryUrl);
        registry.register(registeredProviderUrl);
    }

　　这里传递的registryUrl 和 registeredProviderUrl 如下

zookeeper://192.168.99.100:2181/org.apache.dubbo.registry.RegistryService?application=dubbp-service-impl&dubbo=2.0.2&export=dubbo%3A%2F%2F192.168.99.1%3A20880%2Fcn.qz.dubbo.service.GroupService%3Fanyhost%3Dtrue%26application%3Ddubbp-service-impl%26bean.name%3DServiceBean%3Acn.qz.dubbo.service.GroupService%3A1.0.0%26bind.ip%3D192.168.99.1%26bind.port%3D20880%26deprecated%3Dfalse%26dubbo%3D2.0.2%26dynamic%3Dtrue%26generic%3Dfalse%26interface%3Dcn.qz.dubbo.service.GroupService%26methods%3Dadd%2ClistAll%26pid%3D27024%26qos.enable%3Dfalse%26register%3Dtrue%26release%3D2.7.3%26revision%3D1.0.0%26side%3Dprovider%26timestamp%3D1629276323291%26version%3D1.0.0&pid=27024&qos.enable=false&release=2.7.3&timestamp=1629276323288

dubbo://192.168.99.1:20880/cn.qz.dubbo.service.GroupService?anyhost=true&application=dubbp-service-impl&bean.name=ServiceBean:cn.qz.dubbo.service.GroupService:1.0.0&deprecated=false&dubbo=2.0.2&dynamic=true&generic=false&interface=cn.qz.dubbo.service.GroupService&methods=add,listAll&pid=27024&register=true&release=2.7.3&revision=1.0.0&side=provider&timestamp=1629276323291&version=1.0.0

最后会调用到：org.apache.dubbo.registry.zookeeper.ZookeeperRegistry#doRegister

    @Override
    public void doRegister(URL url) {
        try {
            zkClient.create(toUrlPath(url), url.getParameter(DYNAMIC_KEY, true));
        } catch (Throwable e) {
            throw new RpcException("Failed to register " + url + " to zookeeper " + getUrl() + ", cause: " + e.getMessage(), e);
        }
    }

　　可以看到就是调用zkClient 创建一个临时节点，节点的路径是一开始贴出来的。

补充：服务发布过程中开启NettyServer

上面的调用过程中 org.apache.dubbo.registry.integration.RegistryProtocol#export 代码块中调用org.apache.dubbo.registry.integration.RegistryProtocol#doLocalExport，然后经过一系列调用调用到：org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#export

    @Override
    public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        URL url = invoker.getUrl();

        // export service.
        String key = serviceKey(url);
        DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
        exporterMap.put(key, exporter);

        //export an stub service for dispatching event
        Boolean isStubSupportEvent = url.getParameter(STUB_EVENT_KEY, DEFAULT_STUB_EVENT);
        Boolean isCallbackservice = url.getParameter(IS_CALLBACK_SERVICE, false);
        if (isStubSupportEvent && !isCallbackservice) {
            String stubServiceMethods = url.getParameter(STUB_EVENT_METHODS_KEY);
            if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
                if (logger.isWarnEnabled()) {
                    logger.warn(new IllegalStateException("consumer [" + url.getParameter(INTERFACE_KEY) +
                            "], has set stubproxy support event ,but no stub methods founded."));
                }

            } else {
                stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
            }
        }

        openServer(url);
        optimizeSerialization(url);

        return exporter;
    }

    private void openServer(URL url) {
        // find server.
        String key = url.getAddress();
        //client can export a service which's only for server to invoke
        boolean isServer = url.getParameter(IS_SERVER_KEY, true);
        if (isServer) {
            ExchangeServer server = serverMap.get(key);
            if (server == null) {
                synchronized (this) {
                    server = serverMap.get(key);
                    if (server == null) {
                        serverMap.put(key, createServer(url));
                    }
                }
            } else {
                // server supports reset, use together with override
                server.reset(url);
            }
        }
    }

    private ExchangeServer createServer(URL url) {
        url = URLBuilder.from(url)
                // send readonly event when server closes, it's enabled by default
                .addParameterIfAbsent(CHANNEL_READONLYEVENT_SENT_KEY, Boolean.TRUE.toString())
                // enable heartbeat by default
                .addParameterIfAbsent(HEARTBEAT_KEY, String.valueOf(DEFAULT_HEARTBEAT))
                .addParameter(CODEC_KEY, DubboCodec.NAME)
                .build();
        String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER);

        if (str != null && str.length() > 0 && !ExtensionLoader.getExtensionLoader(Transporter.class).hasExtension(str)) {
            throw new RpcException("Unsupported server type: " + str + ", url: " + url);
        }

        ExchangeServer server;
        try {
            server = Exchangers.bind(url, requestHandler);
        } catch (RemotingException e) {
            throw new RpcException("Fail to start server(url: " + url + ") " + e.getMessage(), e);
        }

        str = url.getParameter(CLIENT_KEY);
        if (str != null && str.length() > 0) {
            Set<String> supportedTypes = ExtensionLoader.getExtensionLoader(Transporter.class).getSupportedExtensions();
            if (!supportedTypes.contains(str)) {
                throw new RpcException("Unsupported client type: " + str);
            }
        }

        return server;
    }

(1) 可以看到openServer 用双重检查判断相关的Server 是否已经开启，也就是从缓存map 中拿，如果没拿到就创建一个Server 开启后存入Map，拿到的key 如下：(可以看到是配置文件配置的dubbo 协议的端口，也就是最后服务监听的端口)

createServer 代码中String str = url.getParameter(SERVER_KEY, DEFAULT_REMOTING_SERVER); 拿到的默认是netty，也就是默认使用netty 建立server

接下来调用到：org.apache.dubbo.remoting.transport.netty4.NettyServer#NettyServer

    public NettyServer(URL url, ChannelHandler handler) throws RemotingException {
        // you can customize name and type of client thread pool by THREAD_NAME_KEY and THREADPOOL_KEY in CommonConstants.
        // the handler will be warped: MultiMessageHandler->HeartbeatHandler->handler
        super(url, ChannelHandlers.wrap(handler, ExecutorUtil.setThreadName(url, SERVER_THREAD_POOL_NAME)));
    }

org.apache.dubbo.remoting.transport.AbstractServer#AbstractServer：

    public AbstractServer(URL url, ChannelHandler handler) throws RemotingException {
        super(url, handler);
        localAddress = getUrl().toInetSocketAddress();

        String bindIp = getUrl().getParameter(Constants.BIND_IP_KEY, getUrl().getHost());
        int bindPort = getUrl().getParameter(Constants.BIND_PORT_KEY, getUrl().getPort());
        if (url.getParameter(ANYHOST_KEY, false) || NetUtils.isInvalidLocalHost(bindIp)) {
            bindIp = ANYHOST_VALUE;
        }
        bindAddress = new InetSocketAddress(bindIp, bindPort);
        this.accepts = url.getParameter(ACCEPTS_KEY, DEFAULT_ACCEPTS);
        this.idleTimeout = url.getParameter(IDLE_TIMEOUT_KEY, DEFAULT_IDLE_TIMEOUT);
        try {
            doOpen();
            if (logger.isInfoEnabled()) {
                logger.info("Start " + getClass().getSimpleName() + " bind " + getBindAddress() + ", export " + getLocalAddress());
            }
        } catch (Throwable t) {
            throw new RemotingException(url.toInetSocketAddress(), null, "Failed to bind " + getClass().getSimpleName()
                    + " on " + getLocalAddress() + ", cause: " + t.getMessage(), t);
        }
        //fixme replace this with better method
        DataStore dataStore = ExtensionLoader.getExtensionLoader(DataStore.class).getDefaultExtension();
        executor = (ExecutorService) dataStore.get(Constants.EXECUTOR_SERVICE_COMPONENT_KEY, Integer.toString(url.getPort()));
    }

会调用org.apache.dubbo.remoting.transport.netty4.NettyServer#doOpen 开启nettyServer (这就是Netty 做Server 的标准流程，建立Worker、BossGroup，然后bind 端口)

    protected void doOpen() throws Throwable {
        bootstrap = new ServerBootstrap();

        bossGroup = new NioEventLoopGroup(1, new DefaultThreadFactory("NettyServerBoss", true));
        workerGroup = new NioEventLoopGroup(getUrl().getPositiveParameter(IO_THREADS_KEY, Constants.DEFAULT_IO_THREADS),
                new DefaultThreadFactory("NettyServerWorker", true));

        final NettyServerHandler nettyServerHandler = new NettyServerHandler(getUrl(), this);
        channels = nettyServerHandler.getChannels();

        bootstrap.group(bossGroup, workerGroup)
                .channel(NioServerSocketChannel.class)
                .childOption(ChannelOption.TCP_NODELAY, Boolean.TRUE)
                .childOption(ChannelOption.SO_REUSEADDR, Boolean.TRUE)
                .childOption(ChannelOption.ALLOCATOR, PooledByteBufAllocator.DEFAULT)
                .childHandler(new ChannelInitializer<NioSocketChannel>() {
                    @Override
                    protected void initChannel(NioSocketChannel ch) throws Exception {
                        // FIXME: should we use getTimeout()?
                        int idleTimeout = UrlUtils.getIdleTimeout(getUrl());
                        NettyCodecAdapter adapter = new NettyCodecAdapter(getCodec(), getUrl(), NettyServer.this);
                        ch.pipeline()//.addLast("logging",new LoggingHandler(LogLevel.INFO))//for debug
                                .addLast("decoder", adapter.getDecoder())
                                .addLast("encoder", adapter.getEncoder())
                                .addLast("server-idle-handler", new IdleStateHandler(0, 0, idleTimeout, MILLISECONDS))
                                .addLast("handler", nettyServerHandler);
                    }
                });
        // bind
        ChannelFuture channelFuture = bootstrap.bind(getBindAddress());
        channelFuture.syncUninterruptibly();
        channel = channelFuture.channel();

    }

1》getUrl 返回的信息如下：

2》getBindAddress() 返回的端口和地址如下

3》可以看到添加的handler 主要有编码解码handler、心跳定时、和核心的NettyServerHandler 处理器。

org.apache.dubbo.remoting.transport.netty4.NettyServerHandler 源码如下：

  1 /*
  2  * Licensed to the Apache Software Foundation (ASF) under one or more
  3  * contributor license agreements.  See the NOTICE file distributed with
  4  * this work for additional information regarding copyright ownership.
  5  * The ASF licenses this file to You under the Apache License, Version 2.0
  6  * (the "License"); you may not use this file except in compliance with
  7  * the License.  You may obtain a copy of the License at
  8  *
  9  *     http://www.apache.org/licenses/LICENSE-2.0
 10  *
 11  * Unless required by applicable law or agreed to in writing, software
 12  * distributed under the License is distributed on an "AS IS" BASIS,
 13  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  * See the License for the specific language governing permissions and
 15  * limitations under the License.
 16  */
 17 package org.apache.dubbo.remoting.transport.netty4;
 18 
 19 import org.apache.dubbo.common.URL;
 20 import org.apache.dubbo.common.logger.Logger;
 21 import org.apache.dubbo.common.logger.LoggerFactory;
 22 import org.apache.dubbo.common.utils.NetUtils;
 23 import org.apache.dubbo.remoting.Channel;
 24 import org.apache.dubbo.remoting.ChannelHandler;
 25 
 26 import io.netty.channel.ChannelDuplexHandler;
 27 import io.netty.channel.ChannelHandlerContext;
 28 import io.netty.channel.ChannelPromise;
 29 import io.netty.handler.timeout.IdleStateEvent;
 30 
 31 import java.net.InetSocketAddress;
 32 import java.util.Map;
 33 import java.util.concurrent.ConcurrentHashMap;
 34 
 35 /**
 36  * NettyServerHandler.
 37  */
 38 @io.netty.channel.ChannelHandler.Sharable
 39 public class NettyServerHandler extends ChannelDuplexHandler {
 40     private static final Logger logger = LoggerFactory.getLogger(NettyServerHandler.class);
 41     /**
 42      * the cache for alive worker channel.
 43      * <ip:port, dubbo channel>
 44      */
 45     private final Map<String, Channel> channels = new ConcurrentHashMap<String, Channel>();
 46 
 47     private final URL url;
 48 
 49     private final ChannelHandler handler;
 50 
 51     public NettyServerHandler(URL url, ChannelHandler handler) {
 52         if (url == null) {
 53             throw new IllegalArgumentException("url == null");
 54         }
 55         if (handler == null) {
 56             throw new IllegalArgumentException("handler == null");
 57         }
 58         this.url = url;
 59         this.handler = handler;
 60     }
 61 
 62     public Map<String, Channel> getChannels() {
 63         return channels;
 64     }
 65 
 66     @Override
 67     public void channelActive(ChannelHandlerContext ctx) throws Exception {
 68         NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
 69         try {
 70             if (channel != null) {
 71                 channels.put(NetUtils.toAddressString((InetSocketAddress) ctx.channel().remoteAddress()), channel);
 72             }
 73             handler.connected(channel);
 74         } finally {
 75             NettyChannel.removeChannelIfDisconnected(ctx.channel());
 76         }
 77     }
 78 
 79     @Override
 80     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
 81         NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
 82         try {
 83             channels.remove(NetUtils.toAddressString((InetSocketAddress) ctx.channel().remoteAddress()));
 84             handler.disconnected(channel);
 85         } finally {
 86             NettyChannel.removeChannelIfDisconnected(ctx.channel());
 87         }
 88     }
 89 
 90     @Override
 91     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
 92         NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
 93         try {
 94             handler.received(channel, msg);
 95         } finally {
 96             NettyChannel.removeChannelIfDisconnected(ctx.channel());
 97         }
 98     }
 99 
100 
101     @Override
102     public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
103         super.write(ctx, msg, promise);
104         NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
105         try {
106             handler.sent(channel, msg);
107         } finally {
108             NettyChannel.removeChannelIfDisconnected(ctx.channel());
109         }
110     }
111 
112     @Override
113     public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
114         // server will close channel when server don't receive any heartbeat from client util timeout.
115         if (evt instanceof IdleStateEvent) {
116             NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
117             try {
118                 logger.info("IdleStateEvent triggered, close channel " + channel);
119                 channel.close();
120             } finally {
121                 NettyChannel.removeChannelIfDisconnected(ctx.channel());
122             }
123         }
124         super.userEventTriggered(ctx, evt);
125     }
126 
127     @Override
128     public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause)
129             throws Exception {
130         NettyChannel channel = NettyChannel.getOrAddChannel(ctx.channel(), url, handler);
131         try {
132             handler.caught(channel, cause);
133         } finally {
134             NettyChannel.removeChannelIfDisconnected(ctx.channel());
135         }
136     }
137 }

View Code

　可以看到核心的处理方法应该在org.apache.dubbo.remoting.transport.netty4.NettyServerHandler#channelRead；

　　心跳检测超时的处理是在org.apache.dubbo.remoting.transport.netty4.NettyServerHandler#userEventTriggered 方法中。

(2) 如果已经开启NettyServer，也就是缓存map 根据key 能拿到服务的信息，就调用下面代码：

server.reset(url);

　　这个代码没做什么实质性的操作。

　　也就是注册多个服务，只会开启一个NettyServer，监听dubbo 协议指定的端口。

总结：

1. 服务注册过程可以大致简单总结为如下：

(1) 引入dubbo 自动配置，会注册一个ServiceAnnotationBeanPostProcessor 对象到Spring容器，该类实现了接口BeanDefinitionRegistryPostProcessor，是一个对象工厂后置处理器

(2) SpringIOC 启动过程中会调用ServiceAnnotationBeanPostProcessor#postProcessBeanDefinitionRegistry，该类主要的逻辑如下：

1》扫描所有带@Service(dubbo 包下) 注解的类，注册到Spring 中，然后每个类都生成一个 ServiceBean 对象，同时也注册到Spring 中。测试可以用下面代码进行测试：

@RestController
public class IndexController {

    @Autowired
    private ApplicationContext applicationContext;

    @GetMapping("/index")
    public void index() {
        String[] beanNamesForType = applicationContext.getBeanNamesForType(ServiceBean.class);
        System.out.println(Arrays.toString(beanNamesForType));
        Arrays.stream(beanNamesForType).forEach(name -> {
            Object bean = applicationContext.getBean(name);
            System.out.println(bean);
        });
    }
}

2》 ServiceBean 实现的接口如下：InitializingBean, DisposableBean, ApplicationContextAware, ApplicationListener<ContextRefreshedEvent>, BeanNameAware, ApplicationEventPublisherAwar，重要的接口是ApplicationListener，在Spring IOC 对象创建完成之后的finishRefresh 会进行事件的发布，也就是会调用到ServiceBean.onApplicationEvent 方法，开始服务的暴露、启动NettyServer等操作。服务注册的过程可以从org.apache.dubbo.config.ServiceConfig#doExportUrls 开始

　　可以看到处理过程中用了大量的模板模式与策略模式。根据不同的URL解析选择对应的策略处理类进行处理。netty在整个体系中的作用就是启动一个NettyServer，端口是dubbo协议指定的端口；核心的NettyHandler 用于处理接收到请求然后调用具体的ServiceImpl 进行处理，这个在下一篇进行研究。

补充：切换注册中心为redis

1. pom 引入如下依赖

        <!--redis 做注册中心-->
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-pool2</artifactId>
            <version>2.6.2</version>
        </dependency>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.6.2</version>
        </dependency>

2. yml 修改配置为redis 注册中心

dubbo:
  application:
    name: dubbp-service-impl
  registry:
    protocol: redis
    address: redis://localhost:6379

3. debug 查看代码

(1) org.apache.dubbo.registry.integration.RegistryProtocol#register 方法获取到的registry 是 org.apache.dubbo.registry.redis.RedisRegistry, 所以暴露远程服务走的是：org.apache.dubbo.registry.redis.RedisRegistry#doRegister

    public void doRegister(URL url) {
        String key = toCategoryPath(url);
        String value = url.toFullString();
        String expire = String.valueOf(System.currentTimeMillis() + expirePeriod);
        boolean success = false;
        RpcException exception = null;
        for (Map.Entry<String, JedisPool> entry : jedisPools.entrySet()) {
            JedisPool jedisPool = entry.getValue();
            try {
                try (Jedis jedis = jedisPool.getResource()) {
                    jedis.hset(key, value, expire);
                    jedis.publish(key, REGISTER);
                    success = true;
                    if (!replicate) {
                        break; //  If the server side has synchronized data, just write a single machine
                    }
                }
            } catch (Throwable t) {
                exception = new RpcException("Failed to register service to redis registry. registry: " + entry.getKey() + ", service: " + url + ", cause: " + t.getMessage(), t);
            }
        }
        if (exception != null) {
            if (success) {
                logger.warn(exception.getMessage(), exception);
            } else {
                throw exception;
            }
        }
    }

(2) 其它启动NettyServer 与之前的一致

补充：为什么要封装一个 invoker对象？

统一暴露出一个可执行体，这样调用者简单的使用它，向它发起 invoke 调用，它内部通过反射或者其他方式进行调用，并对响应结果进行处理，查看invoker 接口如下

public interface Invoker<T> extends Node {

    /**
     * get service interface.
     *
     * @return service interface.
     */
    Class<T> getInterface();

    /**
     * invoke.
     *
     * @param invocation
     * @return result
     * @throws RpcException
     */
    Result invoke(Invocation invocation) throws RpcException;

}

涉及到的Invocation 和 Result 对象如下：(可以看到Result 实现了异步获取任务结果的接口)

  1 package org.apache.dubbo.rpc;
  2 
  3 import java.util.Map;
  4 
  5 /**
  6  * Invocation. (API, Prototype, NonThreadSafe)
  7  *
  8  * @serial Don't change the class name and package name.
  9  * @see org.apache.dubbo.rpc.Invoker#invoke(Invocation)
 10  * @see org.apache.dubbo.rpc.RpcInvocation
 11  */
 12 public interface Invocation {
 13 
 14     /**
 15      * get method name.
 16      *
 17      * @return method name.
 18      * @serial
 19      */
 20     String getMethodName();
 21 
 22     /**
 23      * get parameter types.
 24      *
 25      * @return parameter types.
 26      * @serial
 27      */
 28     Class<?>[] getParameterTypes();
 29 
 30     /**
 31      * get arguments.
 32      *
 33      * @return arguments.
 34      * @serial
 35      */
 36     Object[] getArguments();
 37 
 38     /**
 39      * get attachments.
 40      *
 41      * @return attachments.
 42      * @serial
 43      */
 44     Map<String, String> getAttachments();
 45 
 46     void setAttachment(String key, String value);
 47 
 48     void setAttachmentIfAbsent(String key, String value);
 49 
 50     /**
 51      * get attachment by key.
 52      *
 53      * @return attachment value.
 54      * @serial
 55      */
 56     String getAttachment(String key);
 57 
 58     /**
 59      * get attachment by key with default value.
 60      *
 61      * @return attachment value.
 62      * @serial
 63      */
 64     String getAttachment(String key, String defaultValue);
 65 
 66     /**
 67      * get the invoker in current context.
 68      *
 69      * @return invoker.
 70      * @transient
 71      */
 72     Invoker<?> getInvoker();
 73 
 74 }
 75 
 76 public interface Result extends CompletionStage<Result>, Future<Result>, Serializable {
 77 
 78     /**
 79      * Get invoke result.
 80      *
 81      * @return result. if no result return null.
 82      */
 83     Object getValue();
 84 
 85     void setValue(Object value);
 86 
 87     /**
 88      * Get exception.
 89      *
 90      * @return exception. if no exception return null.
 91      */
 92     Throwable getException();
 93 
 94     void setException(Throwable t);
 95 
 96     /**
 97      * Has exception.
 98      *
 99      * @return has exception.
100      */
101     boolean hasException();
102 
103     /**
104      * Recreate.
105      * <p>
106      * <code>
107      * if (hasException()) {
108      * throw getException();
109      * } else {
110      * return getValue();
111      * }
112      * </code>
113      *
114      * @return result.
115      * @throws if has exception throw it.
116      */
117     Object recreate() throws Throwable;
118 
119     /**
120      * get attachments.
121      *
122      * @return attachments.
123      */
124     Map<String, String> getAttachments();
125 
126     /**
127      * Add the specified map to existing attachments in this instance.
128      *
129      * @param map
130      */
131     void addAttachments(Map<String, String> map);
132 
133     /**
134      * Replace the existing attachments with the specified param.
135      *
136      * @param map
137      */
138     void setAttachments(Map<String, String> map);
139 
140     /**
141      * get attachment by key.
142      *
143      * @return attachment value.
144      */
145     String getAttachment(String key);
146 
147     /**
148      * get attachment by key with default value.
149      *
150      * @return attachment value.
151      */
152     String getAttachment(String key, String defaultValue);
153 
154     void setAttachment(String key, String value);
155 
156     /**
157      * Returns the specified {@code valueIfAbsent} when not complete, or
158      * returns the result value or throws an exception when complete.
159      *
160      * @see CompletableFuture#getNow(Object)
161      */
162     Result getNow(Result valueIfAbsent);
163 
164     /**
165      * Add a callback which can be triggered when the RPC call finishes.
166      * <p>
167      * Just as the method name implies, this method will guarantee the callback being triggered under the same context as when the call was started,
168      * see implementation in {@link Result#whenCompleteWithContext(BiConsumer)}
169      *
170      * @param fn
171      * @return
172      */
173     Result whenCompleteWithContext(BiConsumer<Result, Throwable> fn);
174 
175     default CompletableFuture<Result> completionFuture() {
176         return toCompletableFuture();
177     }
178 }

View Code

补充：每个暴露的service都对应的有一个Invoker，用于接收客户端之后处理后续逻辑

会调用到org.apache.dubbo.rpc.protocol.dubbo.DubboProtocol#export：

    public <T> Exporter<T> export(Invoker<T> invoker) throws RpcException {
        URL url = invoker.getUrl();

        // export service.
        String key = serviceKey(url);
        DubboExporter<T> exporter = new DubboExporter<T>(invoker, key, exporterMap);
        exporterMap.put(key, exporter);

        //export an stub service for dispatching event
        Boolean isStubSupportEvent = url.getParameter(STUB_EVENT_KEY, DEFAULT_STUB_EVENT);
        Boolean isCallbackservice = url.getParameter(IS_CALLBACK_SERVICE, false);
        if (isStubSupportEvent && !isCallbackservice) {
            String stubServiceMethods = url.getParameter(STUB_EVENT_METHODS_KEY);
            if (stubServiceMethods == null || stubServiceMethods.length() == 0) {
                if (logger.isWarnEnabled()) {
                    logger.warn(new IllegalStateException("consumer [" + url.getParameter(INTERFACE_KEY) +
                            "], has set stubproxy support event ,but no stub methods founded."));
                }

            } else {
                stubServiceMethodsMap.put(url.getServiceKey(), stubServiceMethods);
            }
        }

        openServer(url);
        optimizeSerialization(url);

        return exporter;
    }

　　这里会把exporter 缓存到 org.apache.dubbo.rpc.protocol.AbstractProtocol#exporterMap 用于后续处理客户端请求的时候调用。 key 可以理解为每个接口的唯一标识。

参考： https://dubbo.apache.org/zh/blog/2019/10/17/dubbo-%E4%B8%AD%E7%9A%84-url-%E7%BB%9F%E4%B8%80%E6%A8%A1%E5%9E%8B/

dubbo SPI(Service Provider Interface)相关： https://dubbo.apache.org/zh/docsv2.7/dev/source/dubbo-spi/

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原文地址：https://www.cnblogs.com/qlqwjy/p/15143413.html