版本说明
springboot starter : 0.1.1
dubbo版本: 2.6.2
自动配置类
@Configuration
@ConditionalOnProperty(prefix = DUBBO_PREFIX, name = "enabled", matchIfMissing = true, havingValue = "true")
@ConditionalOnClass(AbstractConfig.class)
public class DubboAutoConfiguration {
// 单个dubbo配置绑定bean ， 默认就是单个
@EnableDubboConfig
protected static class SingleDubboConfigConfiguration {
}
/**
* 多个dubbo配置绑定bean , 默认不使用。
*
*/
@ConditionalOnProperty(name = MULTIPLE_CONFIG_PROPERTY_NAME, havingValue = "true")
@EnableDubboConfig(multiple = true)
protected static class MultipleDubboConfigConfiguration {
}
/**
* service类，服务提供者的BeanDefinitionRegistryPostProcessor类，用来解析
* @Service注解，生成Service的BeanDefinition类，放入spring容器，供spring容器生成Bean
*
*/
@ConditionalOnProperty(name = BASE_PACKAGES_PROPERTY_NAME)
@ConditionalOnClass(RelaxedPropertyResolver.class)
@Bean
public ServiceAnnotationBeanPostProcessor serviceAnnotationBeanPostProcessor(Environment environment) {
RelaxedPropertyResolver resolver = new RelaxedPropertyResolver(environment);
Set<String> packagesToScan = resolver.getProperty(BASE_PACKAGES_PROPERTY_NAME, Set.class, emptySet());
return new ServiceAnnotationBeanPostProcessor(packagesToScan);
}
// springboot dataBinder 机制的扩展，用来将具体的属性设置到相应的实体类里面去。
@ConditionalOnClass(RelaxedDataBinder.class)
@Bean
@Scope(scopeName = SCOPE_PROTOTYPE)
public RelaxedDubboConfigBinder relaxedDubboConfigBinder() {
return new RelaxedDubboConfigBinder();
}
/**
* 用来解析@Reference 注解，消费者引用哪些服务，通过这个注解来进行引用
* 给标注这个@Reference注解的属性赋值， 和@autowired的做法类似。
*
*/
@ConditionalOnMissingBean
@Bean(name = ReferenceAnnotationBeanPostProcessor.BEAN_NAME)
public ReferenceAnnotationBeanPostProcessor referenceAnnotationBeanPostProcessor() {
return new ReferenceAnnotationBeanPostProcessor();
}
}
配置说明：
SingleDubboConfigConfiguration ： 引入了单个dubbo配置绑定bean的配置 ， 默认使用
// 配置如下
dubbo.application
dubbo.module
dubbo.registry
dubbo.protocol
dubbo.monitor
dubbo.provider
dubbo.consumer
**MultipleDubboConfigConfiguration ** ：多个dubbo配置绑定bean , 默认不使用。Dubbo @Service 和 @Reference 允许 Dubbo 应用关联ApplicationConfig Bean 或者指定多个RegistryConfig Bean 等能力。换句话说，Dubbo 应用上下文中可能存在多个ApplicationConfig 等 Bean定义。
// 配置如下
dubbo.applications
dubbo.modules
dubbo.registries
dubbo.protocols
dubbo.monitors
dubbo.providers
dubbo.consumers
**serviceAnnotationBeanPostProcessor ** ：解析service类注解的类，如果在spring boot启动类上配置了@DubboComponentScan 则默认不使用。
**referenceAnnotationBeanPostProcessor ** ： 为@Reference注入对象，如果在spring boot启动类上配置了@DubboComponentScan 则默认不使用。
因为在@DubboComponentScan这个注解中引入了DubboComponentScanRegistrar这个注册类，该类中做了解析@service注解和@Reference的事情
@EnableDubboConfig
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@Import(DubboConfigConfigurationSelector.class) // 主要作用是这个
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 false;
}
主要的作用就是导入了这个类DubboConfigConfigurationSelector
DubboConfigConfigurationSelector
public class DubboConfigConfigurationSelector implements ImportSelector, Ordered {
@Override
public String[] selectImports(AnnotationMetadata importingClassMetadata) {
// 获取注解上的属性，这个是通过@EnableDubboConfig导入的，所以AnnotationMetadata里面就包含了这个注解的值
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
importingClassMetadata.getAnnotationAttributes(EnableDubboConfig.class.getName()));
// 是否是多配置，默认为false
boolean multiple = attributes.getBoolean("multiple");
if (multiple) {
return of(DubboConfigConfiguration.Multiple.class.getName());
} else {
// 这里就直接讲解单配置的。
return of(DubboConfigConfiguration.Single.class.getName());
}
}
private static <T> T[] of(T... values) {
return values;
}
@Override
public int getOrder() {
return HIGHEST_PRECEDENCE;
}
}
DubboConfigConfigurationSelector这个类实现了ImportSelector 接口，该接口的selectImports方法就是返回bean的名称，供spring初始化，所以这里返回了
DubboConfigConfiguration.Single.class.getName() ， spring就会初始化这个类了。
Single
DubboConfigConfiguration.Single的代码如下 , 通过@EnableDubboConfigBindings注解，导入了多个@EnableDubboConfigBinding
@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)
})
public static class Single {
}
EnableDubboConfigBindings
由上面可以看到，spring在初始化Single这个类的时候，必然会加载他上面的注解，该类的主要作用就是为了导入它上面的注解，@EnableDubboConfigBindings
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboConfigBindingsRegistrar.class) // 导入了这个类。
public @interface EnableDubboConfigBindings {
/**
* The value of {@link EnableDubboConfigBindings}
*
* @return non-null
*/
EnableDubboConfigBinding[] value();
}
@EnableDubboConfigBindings 注解导入了DubboConfigBindingsRegistrar这个类，该类的作用是将配置属性和dubbo的配置进行绑定。注解的value是7个子注解
@EnableDubboConfigBinding ,后面DubboConfigBindingsRegistrar解析的时候，会获取到这个7个子注解，将对应的属性和dubbo的配置类进行绑定。
DubboConfigBindingsRegistrar
public class DubboConfigBindingsRegistrar implements ImportBeanDefinitionRegistrar, EnvironmentAware {
private ConfigurableEnvironment environment;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
// 获取导入此类的注解信息，@EnableDubboConfigBindings
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
importingClassMetadata.getAnnotationAttributes(EnableDubboConfigBindings.class.getName()));
// 获取@EnableDubboConfigBinding 子注解
AnnotationAttributes[] annotationAttributes = attributes.getAnnotationArray("value");
// 初始化DubboConfigBindingRegistrar类，该类的主要作用就是为了解析单个的@EnableDubboConfigBinding注解
DubboConfigBindingRegistrar registrar = new DubboConfigBindingRegistrar();
registrar.setEnvironment(environment);
for (AnnotationAttributes element : annotationAttributes) {
// 循环注册，通过注解里面的信息，生成Dubbo配置的BeanDefinition，最后放入spring容器中，供spring容器实例化。
registrar.registerBeanDefinitions(element, registry);
}
}
@Override
public void setEnvironment(Environment environment) {
Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
this.environment = (ConfigurableEnvironment) environment;
}
}
注册dubbo的配置bean
protected void registerBeanDefinitions(AnnotationAttributes attributes, BeanDefinitionRegistry registry) {
//1. 从环境 中取出 响应的属性名
String prefix = environment.resolvePlaceholders(attributes.getString("prefix"));
// 2. 获取dubbo的配置类的class
Class<? extends AbstractConfig> configClass = attributes.getClass("type");
// 3. 获取是否是多个dubbo的配置
boolean multiple = attributes.getBoolean("multiple");
// 注册dubbo的配置bean
registerDubboConfigBeans(prefix, configClass, multiple, registry);
}
步骤说明：
1.参数attributes就是@EnableDubboConfigBinding里面的属性，获取prefix属性值，就是获取到了：dubbo.application
例：
@EnableDubboConfigBinding(prefix = "dubbo.application", type = ApplicationConfig.class)
2.获取dubbo的配置类的class，也就是获取到了ApplicationConfig.class
3.获取multiple的值，默认没有配置就是false
4.调用registerDubboConfigBeans方法生成dubbo的配置bean
private void registerDubboConfigBeans(String prefix,
Class<? extends AbstractConfig> configClass,
boolean multiple,
BeanDefinitionRegistry registry) {
// 根据属性名，如：dubbo.application 获取具体的属性值
Map<String, String> properties = getSubProperties(environment.getPropertySources(), prefix);
if (CollectionUtils.isEmpty(properties)) {
// 如果没有配置，则没有必要生成对应的dubbo配置bean了
if (log.isDebugEnabled()) {
log.debug("There is no property for binding to dubbo config class [" + configClass.getName()
+ "] within prefix [" + prefix + "]");
}
return;
}
// BeanName
Set<String> beanNames = multiple ? resolveMultipleBeanNames(properties) :
Collections.singleton(resolveSingleBeanName(properties, configClass, registry));
for (String beanName : beanNames) {
// 生成bena
registerDubboConfigBean(beanName, configClass, registry);
// 注册dubbo的DubboConfigBindingBeanPostProcessor
registerDubboConfigBindingBeanPostProcessor(prefix, beanName, multiple, registry);
}
}
private void registerDubboConfigBean(String beanName, Class<? extends AbstractConfig> configClass,
BeanDefinitionRegistry registry) {
// 生成BeanDefinitionBuilder
BeanDefinitionBuilder builder = rootBeanDefinition(configClass);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
// 通过BeanDefinitionRegistry注册dubbo的配置bean
registry.registerBeanDefinition(beanName, beanDefinition);
if (log.isInfoEnabled()) {
log.info("The dubbo config bean definition [name : " + beanName + ", class : " + configClass.getName() +
"] has been registered.");
}
}
DubboConfigBindingBeanPostProcessor
这个类是在dubbo的配置类初始化完成后会执行响应的方法。用来将属性值设置到对应的属性里面去，在springboot中我们存在这种情况
first-name，firstName, FIRST_NAME ， 比如我们在yaml文件中配置这样的属性，我们的java bean中的属性是firstName , 在使用@ConfigurationProperties
注解的时候我们无需担心，如果不是用springboot自身的config类来注入，那么我们自己处理这种情况就会变的非常麻烦，所以dubbo选择的是通过RelaxedDataBinder类来处理这个问题。这是spring boot的机制。
DubboConfigBindingBeanPostProcessor类实现了BeanPostProcessor,ApplicationContextAware, InitializingBean 这三个接口，下面是挑了一些重要的方法展示出来 ， **每个dubbo配置类都有相应的DubboConfigBindingBeanPostProcessor **
public DubboConfigBindingBeanPostProcessor(String prefix, String beanName) {
Assert.notNull(prefix, "The prefix of Configuration Properties must not be null");
Assert.notNull(beanName, "The name of bean must not be null");
this.prefix = prefix; // 属性前缀
this.beanName = beanName; // dubbo的配置类名
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
// 会在每一个bean实例化之后、初始化（如afterPropertiesSet方法）之前被调用。
if (beanName.equals(this.beanName) && bean instanceof AbstractConfig) {
AbstractConfig dubboConfig = (AbstractConfig) bean;
// 将属性和配置进行绑定
dubboConfigBinder.bind(prefix, dubboConfig);
if (log.isInfoEnabled()) {
log.info("The properties of bean [name : " + beanName + "] have been binding by prefix of " +
"configuration properties : " + prefix);
}
}
return bean;
}
@Override
public void afterPropertiesSet() throws Exception {
// DubboConfigBindingBeanPostProcessor 初始化之后就会执行
if (dubboConfigBinder == null) {
try {
// 从容器中获取DubboConfigBinder ， DubboConfigBinder的作用范围是prototype ， 每次调用getbean都会新创建一个
dubboConfigBinder = applicationContext.getBean(DubboConfigBinder.class);
} catch (BeansException ignored) {
if (log.isDebugEnabled()) {
log.debug("DubboConfigBinder Bean can't be found in ApplicationContext.");
}
// Use Default implementation
dubboConfigBinder = createDubboConfigBinder(applicationContext.getEnvironment());
}
}
dubboConfigBinder.setIgnoreUnknownFields(ignoreUnknownFields);
dubboConfigBinder.setIgnoreInvalidFields(ignoreInvalidFields);
}
dubboConfigBinder的代码如下，下面主要就是调用springboot 的dataBinder机制进行属性设值了
public class RelaxedDubboConfigBinder extends AbstractDubboConfigBinder {
@Override
public <C extends AbstractConfig> void bind(String prefix, C dubboConfig) {
RelaxedDataBinder relaxedDataBinder = new RelaxedDataBinder(dubboConfig);
// Set ignored*
relaxedDataBinder.setIgnoreInvalidFields(isIgnoreInvalidFields());
relaxedDataBinder.setIgnoreUnknownFields(isIgnoreUnknownFields());
//从Environment中获取属性
Map<String, String> properties = getSubProperties(getPropertySources(), prefix);
// 将属性MAP转换为MutablePropertyValues
MutablePropertyValues propertyValues = new MutablePropertyValues(properties);
// 绑定
relaxedDataBinder.bind(propertyValues);
}
}
通过上面的源码，可以看出来，dubbo的配置是一环接着一环，很多时候一个不起眼的地方就是往下走的关键代码，他主要是通过注解的导入配置类，然后通过
BeanDefinitionRegistry生成对应的beanDefintion放入spring容器中。
本文所解析的这些源码均不涉及dubbo的核心功能，仅仅是讲了dubbo启动之后，如何获取到配置，如果进行配置装配，方便大家后续有个好的理解。
有兴趣可以看下一spring的扩展机制，dubbo中都有大量的使用到。
https://nobodyiam.com/2017/02/26/several-ways-to-extend-spring/