spring整合dubbo

前沿

Spring整合dubbo，核心解決三個(gè)問題：

  • 解析配置文件，獲取dubbo需要屬性信息
  • 找到所有@Service，導(dǎo)出服務(wù)到注冊(cè)中心
  • 找到所有@Reference 從注冊(cè)中心獲取實(shí)現(xiàn)服務(wù)并注入

一. 整合核心注解

通過EnableDubbo注解開啟.

@Configuration 
@EnableDubbo(scanBasePackages = "org.apache.dubbo.xxx") 
@PropertySource("classpath:/spring/dubbo-xxx.properties" ) 
static class DubboConfiguration { 
}

EnableDubbo 接口核心注解 @EnableDubboConfig @DubboComponentScan

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@EnableDubboConfig
@DubboComponentScan
public @interface EnableDubbo {
    ... ... ...
}

EnableDubboConfig

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@Import(DubboConfigConfigurationRegistrar.class)
public @interface EnableDubboConfig {

    /**
     * It indicates whether binding to multiple Spring Beans.
     *
     * @return the default value is <code>false</code>
     * @revised 2.5.9
     */
    boolean multiple() default true;

}

DubboComponentScan

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboComponentScanRegistrar.class)
public @interface DubboComponentScan {

    /**
     * Alias for the {@link #basePackages()} attribute. Allows for more concise annotation
     * declarations e.g.: {@code @DubboComponentScan("org.my.pkg")} instead of
     * {@code @DubboComponentScan(basePackages="org.my.pkg")}.
     *
     * @return the base packages to scan
     */
    String[] value() default {};

    /**
     * Base packages to scan for annotated @Service classes. {@link #value()} is an
     * alias for (and mutually exclusive with) this attribute.
     * <p>
     * Use {@link #basePackageClasses()} for a type-safe alternative to String-based
     * package names.
     *
     * @return the base packages to scan
     */
    String[] basePackages() default {};

    /**
     * Type-safe alternative to {@link #basePackages()} for specifying the packages to
     * scan for annotated @Service classes. The package of each class specified will be
     * scanned.
     *
     * @return classes from the base packages to scan
     */
    Class<?>[] basePackageClasses() default {};

}

二. dubbo配置處理核心流程

DubboConfigBean創(chuàng)建流程

參見Spring容器啟動(dòng)流程，不難找到配置處理流程入口DubboConfigConfigurationRegistrar的registerBeanDefinitions

 @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        System.out.println("執(zhí)行DubboConfigConfigurationRegistrar");


        AnnotationAttributes attributes = AnnotationAttributes.fromMap(
                importingClassMetadata.getAnnotationAttributes(EnableDubboConfig.class.getName()));
        // multiple 支持，如支持多個(gè)注冊(cè)中心，多個(gè)協(xié)議等
        boolean multiple = attributes.getBoolean("multiple");

        // Single Config Bindings
        registerBeans(registry, DubboConfigConfiguration.Single.class);

        if (multiple) { // Since 2.6.6 https://github.com/apache/dubbo/issues/3193
            registerBeans(registry, DubboConfigConfiguration.Multiple.class);
        }
    }
// 無論multiple是否為true，核心都是走registerBeans，該方法時(shí)AnnotatedBeanDefinitionRegistryUtils實(shí)現(xiàn)的，通過AnnotatedBeanDefinitionReader的register方法，解析目標(biāo)類上所有注解，進(jìn)行處理
public static void registerBeans(BeanDefinitionRegistry registry, Class<?>... annotatedClasses) {

         ... ... ...

        AnnotatedBeanDefinitionReader reader = new AnnotatedBeanDefinitionReader(registry);

         ... ... ...
        // 利用Spring中的AnnotatedBeanDefinitionReader來解析annotatedClasses
        // 會(huì)解析該類上的注解，然后進(jìn)行處理
        reader.register(annotatedClasses);
    }

** DubboConfigConfiguration**

Single和Multiple 都是注解EnableDubboConfigBindings，只是前綴和multiple屬性不同。

public class DubboConfigConfiguration {

    /**
     * Single Dubbo {@link AbstractConfig Config} Bean Binding
     */
    @EnableDubboConfigBindings({
            @EnableDubboConfigBinding(prefix = "dubbo.application", type = ApplicationConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.module", type = ModuleConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.registry", type = RegistryConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.protocol", type = ProtocolConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.monitor", type = MonitorConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.provider", type = ProviderConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.consumer", type = ConsumerConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.config-center", type = ConfigCenterBean.class),
            @EnableDubboConfigBinding(prefix = "dubbo.metadata-report", type = MetadataReportConfig.class),
            @EnableDubboConfigBinding(prefix = "dubbo.metrics", type = MetricsConfig.class)
    })
    public static class Single {

    }

    /**
     * Multiple Dubbo {@link AbstractConfig Config} Bean Binding
     */
    @EnableDubboConfigBindings({
            @EnableDubboConfigBinding(prefix = "dubbo.applications", type = ApplicationConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.modules", type = ModuleConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.registries", type = RegistryConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.protocols", type = ProtocolConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.monitors", type = MonitorConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.providers", type = ProviderConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.consumers", type = ConsumerConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.config-centers", type = ConfigCenterBean.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.metadata-reports", type = MetadataReportConfig.class, multiple = true),
            @EnableDubboConfigBinding(prefix = "dubbo.metricses", type = MetricsConfig.class, multiple = true)
    })
    public static class Multiple {

    }
}

EnableDubboConfigBinding

EnableDubboConfigBinding上導(dǎo)入DubboConfigBindingsRegistrar

@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboConfigBindingsRegistrar.class)
public @interface EnableDubboConfigBindings {

    /**
     * The value of {@link EnableDubboConfigBindings}
     *
     * @return non-null
     */
    EnableDubboConfigBinding[] value();

}

DubboConfigBindingsRegistrar

DubboConfigBindingsRegistrar 實(shí)現(xiàn)了ImportBeanDefinitionRegistrar，會(huì)調(diào)用registerBeanDefinitions，獲取所有的注解，逐個(gè)解析處理。

public class DubboConfigBindingsRegistrar implements ImportBeanDefinitionRegistrar, EnvironmentAware {

    private ConfigurableEnvironment environment;

    @Override
    public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
        System.out.println("執(zhí)行DubboConfigBindingsRegistrar");
        AnnotationAttributes attributes = AnnotationAttributes.fromMap(
                importingClassMetadata.getAnnotationAttributes(EnableDubboConfigBindings.class.getName()));

        // 拿到多個(gè)@EnableDubboConfigBinding注解
        AnnotationAttributes[] annotationAttributes = attributes.getAnnotationArray("value");

        DubboConfigBindingRegistrar registrar = new DubboConfigBindingRegistrar();
        registrar.setEnvironment(environment);

        for (AnnotationAttributes element : annotationAttributes) {

            // 逐個(gè)解析@EnableDubboConfigBinding注解，比如@EnableDubboConfigBinding(prefix = "dubbo.application", type = ApplicationConfig.class)
            registrar.registerBeanDefinitions(element, registry);

        }
    }
}

逐個(gè)解析EnableDubboConfigBinding

protected void registerBeanDefinitions(AnnotationAttributes attributes, BeanDefinitionRegistry registry) {

        // prefix = "dubbo.application"
        String prefix = environment.resolvePlaceholders(attributes.getString("prefix"));

        // type = ApplicationConfig.class
        Class<? extends AbstractConfig> configClass = attributes.getClass("type");

        boolean multiple = attributes.getBoolean("multiple");

        registerDubboConfigBeans(prefix, configClass, multiple, registry);

    }

registerDubboConfigBeans

核心處理方法。按前綴生成不同的beanName。循環(huán)所有beamNames，執(zhí)行

  • registerDubboConfigBean

不是真正的注冊(cè)Bean，只是注冊(cè)BeanDefinition。Spring容器啟動(dòng)過程中會(huì)根據(jù)這些BeanDefinition生成相應(yīng)的Bean。

  • registerDubboConfigBindingBeanPostProcessor

注冊(cè)后置處理器

private void registerDubboConfigBeans(String prefix,
                                          Class<? extends AbstractConfig> configClass,
                                          boolean multiple,
                                          BeanDefinitionRegistry registry) {

        // 從properties文件中根據(jù)前綴拿對(duì)應(yīng)的配置項(xiàng)，比如根據(jù)dubbo.application前綴，
        // 就可以拿到：
        // dubbo.application.name=dubbo-demo-provider-application
        // dubbo.application.logger=log4j
        Map<String, Object> properties = getSubProperties(environment.getPropertySources(), prefix);

        // 如果沒有相關(guān)的配置項(xiàng)，則不需要注冊(cè)BeanDefinition
        if (CollectionUtils.isEmpty(properties)) {
            if (log.isDebugEnabled()) {
                log.debug("There is no property for binding to dubbo config class [" + configClass.getName()
                        + "] within prefix [" + prefix + "]");
            }
            return;
        }

        // 根據(jù)配置項(xiàng)生成beanNames，為什么會(huì)有多個(gè)？
        // 普通情況一個(gè)dubbo.application前綴對(duì)應(yīng)一個(gè)ApplicationConfig類型的Bean
        // 特殊情況下，比如dubbo.protocols對(duì)應(yīng)了：
//        dubbo.protocols.p1.name=dubbo
//        dubbo.protocols.p1.port=20880
//        dubbo.protocols.p1.host=0.0.0.0

//        dubbo.protocols.p2.name=http
//        dubbo.protocols.p2.port=8082
//        dubbo.protocols.p2.host=0.0.0.0
        // 那么就需要對(duì)應(yīng)兩個(gè)ProtocolConfig類型的Bean，那么就需要兩個(gè)beanName:p1和p2

        // 這里就是multiple為true或false的區(qū)別，名字的區(qū)別，根據(jù)multiple用來判斷是否從配置項(xiàng)中獲取beanName
        // 如果multiple為false，則看有沒有配置id屬性，如果沒有配置則自動(dòng)生成一個(gè)beanName.
        Set<String> beanNames = multiple ? resolveMultipleBeanNames(properties) :
                Collections.singleton(resolveSingleBeanName(properties, configClass, registry));

        for (String beanName : beanNames) {

            // 為每個(gè)beanName,注冊(cè)一個(gè)空的BeanDefinition
            registerDubboConfigBean(beanName, configClass, registry);

            // 為每個(gè)bean注冊(cè)一個(gè)DubboConfigBindingBeanPostProcessor的Bean后置處理器
            registerDubboConfigBindingBeanPostProcessor(prefix, beanName, multiple, registry);

        }

        // 注冊(cè)一個(gè)NamePropertyDefaultValueDubboConfigBeanCustomizer的bean
        registerDubboConfigBeanCustomizers(registry);

    }

DubboConfigBindingBeanPostProcessor

這個(gè)后置處理器實(shí)現(xiàn)了BeanDefinitionRegistryPostProcessor，在Bean初始化之前Spring調(diào)用postProcessBeforeInitialization，將配置文件中的屬性放入Bean實(shí)例中

public class DubboConfigBindingBeanPostProcessor implements BeanPostProcessor, ApplicationContextAware, InitializingBean
        , BeanDefinitionRegistryPostProcessor {
     ... ... ...
     @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {

        // 每個(gè)XxConfig對(duì)應(yīng)一個(gè)BeanPostProcessor，所以每個(gè)DubboConfigBindingBeanPostProcessor只處理對(duì)應(yīng)的beanName

        if (this.beanName.equals(beanName) && bean instanceof AbstractConfig) {

            AbstractConfig dubboConfig = (AbstractConfig) bean;
            // 從properties文件中獲取值，并設(shè)置到dubboConfig對(duì)象中
            bind(prefix, dubboConfig);

            // 設(shè)置dubboConfig對(duì)象的name屬性，設(shè)置為beanName
            customize(beanName, dubboConfig);

        }

        return bean;

    }
   ... ... ...
}

三. @Service 處理

核心邏輯：

    1. 擴(kuò)展BeanFactoryBeanPostProcessor,實(shí)現(xiàn)掃描所有@Service，注冊(cè)BeanDefinition
    1. 通過注冊(cè)的Bean類型ServiceBean 實(shí)現(xiàn)Spring監(jiān)聽器接口，監(jiān)聽容器完成啟動(dòng)。在容器啟動(dòng)后最終執(zhí)行export方法，暴露接口
Spring整合dubbo服務(wù)暴露

四. @Reference 處理

類似Autowired 實(shí)現(xiàn)，

    1. 只是實(shí)例化時(shí)傳遞自己關(guān)心的注解
    1. 實(shí)例化后初始化前(Autowired之前)，執(zhí)行 postProcessPropertyValues
    1. 生成一個(gè)代理對(duì)象，然后注入到屬性中。其中這個(gè)代理對(duì)象時(shí)dubbo的ReferenceConfig 生成的 Invoker， 這個(gè)Invoker 持有注冊(cè)服務(wù)信息，最終完成遠(yuǎn)程RPC調(diào)用
image.png

五. 總結(jié)

Spring整合dubbo
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