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JavaYouth/docs/dubbo-sourcecode-v1/04.Dubbo源码系列V1-Dubbo第四节-Spring与Dubbo整合原理与源码分析.md
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---
title: 04.Dubbo源码系列V1-Dubbo第四节-Spring与Dubbo整合原理与源码分析
tags:
- Dubbo
- rpc
categories:
- rpc
- Dubbo源码系列v1
keywords: Dubbo，rpc
description: Spring与Dubbo整合原理与源码分析
cover: 'https://npm.elemecdn.com/lql_static@latest/logo/dubbo.png'
abbrlink: 796f395d
date: 2021-10-06 13:21:58
---
## 第四节: Spring与Dubbo整合原理与源码分析
### 笔记更新地址：
[https://www.yuque.com/books/share/f2394ae6-381b-4f44-819e-c231b39c1497](https://www.yuque.com/books/share/f2394ae6-381b-4f44-819e-c231b39c1497?#)（密码：kyys） 《Dubbo笔记》
### 整体架构和流程
<img src="https://npm.elemecdn.com/youthlql@1.0.4/rpc/dubbo/v1/04_di_si_jie/Spring整合Dubbo架构图.png"/>
#### 处理@Service
1. Dubbo的@Service注解Spring的@Service注解重名了，dubbo在2.7版本之后改成了@DubboService注解。
> 在Dubbo的文章中如果不是特别说明@Service注解均为Dubbo的注解
2. Dubbo在处理@Service注解时会生成两个对象，看上面的图，DemoServiceImpl这个是给Spring容器生成的，意思就是@Service注解兼具了Spring@Service注解的功能。同时@Serivce注解会再生成一个ServiceBean类型的对象，这个对象会做一些事情，比如：将对应的服务类注册到注册中心，将service服务进行分组，分版本，控制超时，权重等等。@Service注解上面写的参数，都是由ServiceBean类型的对象来承接。当调用ServiceBean类型里面的export方法就可以控制服务的注册。
3. ServiceBean的父类里有一个ref属性，指向这个服务的实现类
#### 处理Properties文件
```properties
# 这个会被解析成ApplicationConfig对象
dubbo.application.name=dubbo-demo-provider1-application
dubbo.application.logger=log4j
dubbo.application.timeout=3000
# 这个会被解析成ProtocolConfig
dubbo.protocols.p1.name=dubbo
dubbo.protocols.p1.port=20880
dubbo.protocols.p1.host=0.0.0.0
dubbo.protocols.p2.name=dubbo
dubbo.protocols.p2.port=20881
dubbo.protocols.p2.host=0.0.0.0
# 这个会被解析成RegistrieConfig
dubbo.registries.r1.address=zookeeper://127.0.0.1:2181
dubbo.registries.r1.timeout=3000
# 等等
```
这些xxxConfig最后都会赋值给ServiceBean里相应的属性
### 实例解析
应用启动类与配置
```java
public class Application {
public static void main(String[] args) throws Exception {
AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(ProviderConfiguration.class);
context.start();
System.in.read();
}
@Configuration
@EnableDubbo(scanBasePackages = "org.apache.dubbo.demo.provider")
@PropertySource("classpath:/spring/dubbo-provider.properties")
static class ProviderConfiguration {
}
}
```
应用配置类为ProviderConfiguration, 在配置上有两个比较重要的注解
1. @PropertySource表示将dubbo-provider.properties中的配置项添加到Spring容器中，可以通过@Value的方式获取到配置项中的值
2. @EnableDubbo(scanBasePackages = "org.apache.dubbo.demo.provider")表示对指定包下的类进行扫描，扫描@Service与@Reference注解，并且进行处理
### @EnableDubbo
在EnableDubbo注解上，有另外两个注解，也是研究Dubbo最重要的两个注解
1. @EnableDubboConfig
2. @DubboComponentScan
```java
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
@Import(DubboConfigConfigurationRegistrar.class)
public @interface EnableDubboConfig {
boolean multiple() default true;
}
//解析properties文件 ===> xxxConfig
```
```java
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboComponentScanRegistrar.class)
public @interface DubboComponentScan {
String[] value() default {};
String[] basePackages() default {};
Class<?>[] basePackageClasses() default {};
}
//解析@Service @Refrence注解
```
注意两个注解中对应的@Import注解所导入的类：
1. DubboConfigConfigurationRegistrar
2. DubboComponentScanRegistrar
Spring在启动时会解析这两个注解，并且执行对应的Registrar类中的registerBeanDefinitions方法（这是Spring中提供的扩展功能。）
### DubboConfigConfigurationRegistrar
```java
public class DubboConfigConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
System.out.println("执行DubboConfigConfigurationRegistrar");
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
importingClassMetadata.getAnnotationAttributes(EnableDubboConfig.class.getName()));
boolean multiple = attributes.getBoolean("multiple"); // 拿EnableDubboConfig里的默认值
// Single Config Bindings
registerBeans(registry, DubboConfigConfiguration.Single.class);
// 默认为true
if (multiple) { // Since 2.6.6 https://github.com/apache/dubbo/issues/3193
registerBeans(registry, DubboConfigConfiguration.Multiple.class);
}
}
}
```
#### 流程
<img src="https://npm.elemecdn.com/youthlql@1.0.4/rpc/dubbo/v1/04_di_si_jie/Spring整合Dubbo只properties文件解析流程.png"/>
Spring启动时，会调用DubboConfigConfigurationRegistrar的registerBeanDefinitions方法，该方法是利用Spring中的AnnotatedBeanDefinitionReader来读取：
1. DubboConfigConfiguration.Single.**class**
2. DubboConfigConfiguration.Multiple.**class**
这两个类上的注解。
```java
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 {
}
}
```
大概意思就是什么前缀的注解，对应解析到哪个类的对象里。
这两个类主要用到的就是@EnableDubboConfigBindings注解：
```java
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(DubboConfigBindingsRegistrar.class)
public @interface EnableDubboConfigBindings {
/**
* The value of {@link EnableDubboConfigBindings}
*
* @return non-null
*/
EnableDubboConfigBinding[] value();
}
```
@EnableDubboConfigBindings注解上也有一个@Import注解，导入的是DubboConfigBindingsRegistrar.**class**。该类会获取@EnableDubboConfigBindings注解中的value，也就是多个@EnableDubboConfigBinding注解，然后利用DubboConfigBindingRegistrar去处理这些@EnableDubboConfigBinding注解。
#### DubboConfigBindingRegistrar
##### 此类总结
此类中的主要方法是registerDubboConfigBeans()方法，主要功能就是获取用户所设置的properties文件中的内容，对Properties文件进行解析，根据Properties文件的每个配置项的前缀、参数名、参数值生成对应的BeanDefinition。
比如：
```java
dubbo.application.name=dubbo-demo-provider1-application
dubbo.application.logger=log4j
```
前缀为"dubbo.application"的配置项，会生成一个ApplicationConfig类型的BeanDefinition，并且name和logger属性为对应的值。
再比如：
```java
dubbo.protocols.p1.name=dubbo
dubbo.protocols.p1.port=20880
dubbo.protocols.p1.host=0.0.0.0
dubbo.protocols.p2.name=dubbo
dubbo.protocols.p2.port=20881
dubbo.protocols.p2.host=0.0.0.0
```
比如前缀为"dubbo.protocols"的配置项，会生成**两**个ProtocolConfig类型的BeanDefinition，两个BeanDefinition的beanName分别为p1和p2。
并且还会针对生成的每个BeanDefinition生成一个和它一对一绑定的BeanPostProcessor，类型为DubboConfigBindingBeanPostProcessor.**class**。
##### 代码注释
> 整个类的代码注释
```java
/**
* {@link AbstractConfig Dubbo Config} binding Bean registrar
*
* @see EnableDubboConfigBinding
* @see DubboConfigBindingBeanPostProcessor
* @since 2.5.8
*/
public class DubboConfigBindingRegistrar implements ImportBeanDefinitionRegistrar, EnvironmentAware {
private final Log log = LogFactory.getLog(getClass());
private ConfigurableEnvironment environment;
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
System.out.println("执行DubboConfigBindingRegistrar");
AnnotationAttributes attributes = AnnotationAttributes.fromMap(
importingClassMetadata.getAnnotationAttributes(EnableDubboConfigBinding.class.getName()));
registerBeanDefinitions(attributes, registry);
}
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);
}
private void registerDubboConfigBeans(String prefix,
Class<? extends AbstractConfig> configClass,
boolean multiple,
BeanDefinitionRegistry registry) {
// 从properties文件中根据前缀拿对应的配置项，比如根据dubbo.application前缀，
// 就可以拿到：
// dubbo.application.name=dubbo-demo-provider-application
// dubbo.application.logger=log4j
Map<String, Object> properties = getSubProperties(environment.getPropertySources(), prefix);
// 如果没有相关的配置项，则不需要注册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;
}
// 根据配置项生成beanNames，为什么会有多个？
// 普通情况一个dubbo.application前缀对应一个ApplicationConfig类型的Bean
// 特殊情况下，比如dubbo.protocols对应了：
// 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
// 那么就需要对应两个ProtocolConfig类型的Bean，那么就需要两个beanName:p1和p2
// 这里就是multiple为true或false的区别，名字的区别，根据multiple用来判断是否从配置项中获取beanName
// 如果multiple为false，则看有没有配置id属性，如果没有配置则自动生成一个beanName.
Set<String> beanNames = multiple ? resolveMultipleBeanNames(properties) :
Collections.singleton(resolveSingleBeanName(properties, configClass, registry));
for (String beanName : beanNames) {
// 为每个beanName,注册一个空的BeanDefinition
registerDubboConfigBean(beanName, configClass, registry);
// 为每个bean注册一个DubboConfigBindingBeanPostProcessor的Bean后置处理器
registerDubboConfigBindingBeanPostProcessor(prefix, beanName, multiple, registry);
}
// 注册一个NamePropertyDefaultValueDubboConfigBeanCustomizer的bean
// 用来把某个XxConfig所对应的beanName设置到name属性中去
registerDubboConfigBeanCustomizers(registry);
}
private void registerDubboConfigBean(String beanName, Class<? extends AbstractConfig> configClass,
BeanDefinitionRegistry registry) {
BeanDefinitionBuilder builder = rootBeanDefinition(configClass);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
registry.registerBeanDefinition(beanName, beanDefinition); // ApplicatinoConfig对象
if (log.isInfoEnabled()) {
log.info("The dubbo config bean definition [name : " + beanName + ", class : " + configClass.getName() +
"] has been registered.");
}
}
private void registerDubboConfigBindingBeanPostProcessor(String prefix, String beanName, boolean multiple,
BeanDefinitionRegistry registry) {
// 注册一个DubboConfigBindingBeanPostProcessor的Bean
// 每个XxConfig的Bean对应一个DubboConfigBindingBeanPostProcessor的Bean
// 比如，一个ApplicationConfig对应一个DubboConfigBindingBeanPostProcessor，
// 一个ProtocolConfig也会对应一个DubboConfigBindingBeanPostProcessor
// 在构造DubboConfigBindingBeanPostProcessor的时候会指定构造方法的值，这样就可以区别开来了
Class<?> processorClass = DubboConfigBindingBeanPostProcessor.class;
BeanDefinitionBuilder builder = rootBeanDefinition(processorClass);
// 真实的前缀，比如dubbo.registries.r2
String actualPrefix = multiple ? normalizePrefix(prefix) + beanName : prefix;
// 添加两个构造方法参数值，所以会调用DubboConfigBindingBeanPostProcessor的两个参数的构造方法
builder.addConstructorArgValue(actualPrefix).addConstructorArgValue(beanName);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
beanDefinition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
registerWithGeneratedName(beanDefinition, registry);
if (log.isInfoEnabled()) {
log.info("The BeanPostProcessor bean definition [" + processorClass.getName()
+ "] for dubbo config bean [name : " + beanName + "] has been registered.");
}
}
private void registerDubboConfigBeanCustomizers(BeanDefinitionRegistry registry) {
registerInfrastructureBean(registry, BEAN_NAME, NamePropertyDefaultValueDubboConfigBeanCustomizer.class);
}
@Override
public void setEnvironment(Environment environment) {
Assert.isInstanceOf(ConfigurableEnvironment.class, environment);
this.environment = (ConfigurableEnvironment) environment;
}
private Set<String> resolveMultipleBeanNames(Map<String, Object> properties) {
Set<String> beanNames = new LinkedHashSet<String>();
// 比如dubbo.protocols.p1.name=dubbo的propertyName为p1.name
for (String propertyName : properties.keySet()) {
// propertyName为p1.name
int index = propertyName.indexOf(".");
if (index > 0) {
// 截取beanName名字为p1
String beanName = propertyName.substring(0, index);
beanNames.add(beanName);
}
}
return beanNames;
}
private String resolveSingleBeanName(Map<String, Object> properties, Class<? extends AbstractConfig> configClass,
BeanDefinitionRegistry registry) {
// 配置了dubbo.application.id=appl，那么appl就是beanName
String beanName = (String) properties.get("id");
// 如果beanName为null，则会进入if分支，由spring自动生成一个beanName,比如org.apache.dubbo.config.ApplicationConfig#0
if (!StringUtils.hasText(beanName)) {
BeanDefinitionBuilder builder = rootBeanDefinition(configClass);
beanName = BeanDefinitionReaderUtils.generateBeanName(builder.getRawBeanDefinition(), registry);
}
return beanName;
}
}
```
#### DubboConfigBindingBeanPostProcessor
DubboConfigBindingBeanPostProcessor是一个BeanPostProcessor，在Spring启动过程中，会针对所有的Bean对象进行后置加工，但是在DubboConfigBindingBeanPostProcessor中有如下判断：
```java
if (this.beanName.equals(beanName) && bean instanceof AbstractConfig)
```
所以DubboConfigBindingBeanPostProcessor并不会处理Spring容器中的所有Bean，它只会处理上文由Dubbo所生成的Bean对象。
并且，在afterPropertiesSet()方法中，会先创建一个DefaultDubboConfigBinder。
##### 代码注释
> 只留了关键性的代码注释，其余省略
```java
/**
* Dubbo Config Binding {@link BeanPostProcessor}
*
* @see EnableDubboConfigBinding
* @see DubboConfigBindingRegistrar
* @since 2.5.8
*/
public class DubboConfigBindingBeanPostProcessor implements BeanPostProcessor, ApplicationContextAware, InitializingBean
, BeanDefinitionRegistryPostProcessor {
private final Log log = LogFactory.getLog(getClass());
/**
* The prefix of Configuration Properties
*/
private final String prefix;
/**
* Binding Bean Name
*/
private final String beanName;
private DubboConfigBinder dubboConfigBinder;
private ApplicationContext applicationContext;
private BeanDefinitionRegistry beanDefinitionRegistry;
private boolean ignoreUnknownFields = true;
private boolean ignoreInvalidFields = true;
private List<DubboConfigBeanCustomizer> configBeanCustomizers = Collections.emptyList();
/**
* @param prefix the prefix of Configuration Properties
* @param beanName the binding Bean Name
*/
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;
this.beanName = beanName;
}
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
/*
1.每个XxConfig对应一个BeanPostProcessor，所以每个DubboConfigBindingBeanPostProcessor只处理对应的beanName
2.阿里这里的代码写的很不好，没必要为每一个Bean都生成一个BeanPostProcessor，多余的加这个if判断，每一个Bean
都会经过Dubbo生成的BeanPostProcessor，不停的if判断，直到找到自己的BeanPostProcessor。还好Dubbo后面的版本
把这里改了。
3.看过Spring源码的应该知道Spring的BeanPostProcessor是所有对象公用的，这种处理就比较好.
*/
if (this.beanName.equals(beanName) && bean instanceof AbstractConfig) {
AbstractConfig dubboConfig = (AbstractConfig) bean;
// 从properties文件中获取值，并设置到dubboConfig对象中
bind(prefix, dubboConfig);
// 设置dubboConfig对象的name属性，设置为beanName
customize(beanName, dubboConfig);
}
return bean;
}
private void bind(String prefix, AbstractConfig dubboConfig) {
dubboConfigBinder.bind(prefix, dubboConfig);
if (log.isInfoEnabled()) {
log.info("The properties of bean [name : " + beanName + "] have been binding by prefix of " +
"configuration properties : " + prefix);
}
}
private void customize(String beanName, AbstractConfig dubboConfig) {
for (DubboConfigBeanCustomizer customizer : configBeanCustomizers) {
customizer.customize(beanName, dubboConfig);
}
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (bean instanceof AbstractConfig) {
// 添加别名，id属性的值为别名
String id = ((AbstractConfig) bean).getId();
if (beanDefinitionRegistry != null && beanDefinitionRegistry instanceof DefaultListableBeanFactory) {
DefaultListableBeanFactory factory = (DefaultListableBeanFactory) beanDefinitionRegistry;
if (!StringUtils.isBlank(id) && !factory.hasAlias(beanName, id)) {
beanDefinitionRegistry.registerAlias(beanName, id);
}
}
}
return bean;
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
//这里建议看看Spring源码
@Override
public void afterPropertiesSet() throws Exception {
initDubboConfigBinder(); // 创建DefaultDubboConfigBinder
initConfigBeanCustomizers();
}
private void initDubboConfigBinder() {
if (dubboConfigBinder == null) {
try {
// 先从Spring容器中获取DubboConfigBinder，默认获取不到
dubboConfigBinder = applicationContext.getBean(DubboConfigBinder.class);
} catch (BeansException ignored) {
if (log.isDebugEnabled()) {
log.debug("DubboConfigBinder Bean can't be found in ApplicationContext.");
}
// Use Default implementation
// 生成一个默认的
dubboConfigBinder = createDubboConfigBinder(applicationContext.getEnvironment());
}
}
dubboConfigBinder.setIgnoreUnknownFields(ignoreUnknownFields);
dubboConfigBinder.setIgnoreInvalidFields(ignoreInvalidFields);
}
private void initConfigBeanCustomizers() {
// 得到之前创建了的NamePropertyDefaultValueDubboConfigBeanCustomizer
Collection<DubboConfigBeanCustomizer> configBeanCustomizers =
beansOfTypeIncludingAncestors(applicationContext, DubboConfigBeanCustomizer.class).values();
this.configBeanCustomizers = new ArrayList<>(configBeanCustomizers);
AnnotationAwareOrderComparator.sort(this.configBeanCustomizers);
}
/**
* Create {@link DubboConfigBinder} instance.
*
* @param environment
* @return {@link DefaultDubboConfigBinder}
*/
protected DubboConfigBinder createDubboConfigBinder(Environment environment) {
DefaultDubboConfigBinder defaultDubboConfigBinder = new DefaultDubboConfigBinder();
defaultDubboConfigBinder.setEnvironment(environment);
return defaultDubboConfigBinder;
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
if (this.beanDefinitionRegistry == null) {
this.beanDefinitionRegistry = registry;
}
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
//do nothing here
}
}
```
#### DefaultDubboConfigBinder
当某个AbstractConfig类型的Bean，在经过DubboConfigBindingBeanPostProcessor处理时，此时Bean对象中的属性是没有值的，会利用DefaultDubboConfigBinder进行赋值。底层就是利用Spring中的DataBinder技术，结合properties文件对对应的属性进行赋值。
对应一个AbstractConfig类型（针对的其实是子类，比如ApplicationConfig、RegistryConfig）的Bean，每个类都有一些属性，而properties文件是一个key-value对，所以实际上DataBinder就是将属性名和properties文件中的key进行匹配，如果匹配成功，则把value赋值给属性。具体DataBinder技术是如何工作的，请自行学习（不难）。
举个例子：
```java
dubbo.application.name=dubbo-demo-provider1-application
dubbo.application.logger=log4j
```
对于此配置，它对应ApplicationConfig对象（beanName是自动生成的），所以最终ApplicationConfig对象的name属性的值为“dubbo-demo-provider1-application”，logger属性的值为“log4j”。
对于
```java
dubbo.protocols.p1.name=dubbo
dubbo.protocols.p1.port=20880
dubbo.protocols.p1.host=0.0.0.0
```
它对应ProtocolConfig对象（beanName为p1）,所以最终ProtocolConfig对象的name属性的值为“dubbo”，port属性的值为20880，host属性的值为“0.0.0.0”。
这样就完成了对properties文件的解析。
```java
public class DefaultDubboConfigBinder extends AbstractDubboConfigBinder {
@Override
public <C extends AbstractConfig> void bind(String prefix, C dubboConfig) {
DataBinder dataBinder = new DataBinder(dubboConfig);
// Set ignored*
dataBinder.setIgnoreInvalidFields(isIgnoreInvalidFields());
dataBinder.setIgnoreUnknownFields(isIgnoreUnknownFields());
// Get properties under specified prefix from PropertySources
// getPropertySources()会拿到由@PropertySource注入进来的properties文件中的内容
// 同时还包括当前java的所有环境变量，包括手动通过-D添加的配置
Map<String, Object> properties = getSubProperties(getPropertySources(), prefix);
// Convert Map to MutablePropertyValues
MutablePropertyValues propertyValues = new MutablePropertyValues(properties);
// Bind
dataBinder.bind(propertyValues);
}
}
```
#### 总结
DubboConfigConfigurationRegistrar的主要作用就是对propties文件进行解析并根据不同的配置项项生成对应类型的Bean对象。
### DubboComponentScanRegistrar
DubboConfigConfigurationRegistrar的作用是向Spring容器中注册两个Bean:
1. ServiceAnnotationBeanPostProcessor
2. ReferenceAnnotationBeanPostProcessor
#### 代码注释
> 部分代码注释
```java
/**
* Dubbo {@link DubboComponentScan} Bean Registrar
*
* @see Service
* @see DubboComponentScan
* @see ImportBeanDefinitionRegistrar
* @see ServiceAnnotationBeanPostProcessor
* @see ReferenceAnnotationBeanPostProcessor
* @since 2.5.7
*/
public class DubboComponentScanRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
System.out.println("执行DubboComponentScanRegistrar");
// 拿到DubboComponentScan注解所定义的包路径，扫描该package下的类，识别这些类上
Set<String> packagesToScan = getPackagesToScan(importingClassMetadata);
// 注册ServiceAnnotationBeanPostProcessor一个Bean
// 实现了BeanDefinitionRegistryPostProcessor接口，所以在Spring启动时会调用postProcessBeanDefinitionRegistry方法
// 该方法会进行扫描，扫描@Service注解了的类，然后生成BeanDefinition（会生成两个，一个普通的bean，一个ServiceBean），后续的Spring周期中会生成Bean
// 在ServiceBean中会监听ContextRefreshedEvent事件，一旦Spring启动完后，就会进行服务导出
registerServiceAnnotationBeanPostProcessor(packagesToScan, registry);
// 注册ReferenceAnnotationBeanPostProcessor
// 实现了AnnotationInjectedBeanPostProcessor接口，继而实现了InstantiationAwareBeanPostProcessorAdapter接口
// 所以Spring在启动时，在对属性进行注入时会调用AnnotationInjectedBeanPostProcessor接口中的postProcessPropertyValues方法
// 在这个过程中会按照@Reference注解的信息去生成一个RefrenceBean对象
registerReferenceAnnotationBeanPostProcessor(registry);
}
/**
* Registers {@link ServiceAnnotationBeanPostProcessor}
*
* @param packagesToScan packages to scan without resolving placeholders
* @param registry {@link BeanDefinitionRegistry}
* @since 2.5.8
*/
private void registerServiceAnnotationBeanPostProcessor(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
// 生成一个RootBeanDefinition，对应的beanClass为ServiceAnnotationBeanPostProcessor.class
BeanDefinitionBuilder builder = rootBeanDefinition(ServiceAnnotationBeanPostProcessor.class);
// 将包路径作为在构造ServiceAnnotationBeanPostProcessor时调用构造方法时的传入参数
builder.addConstructorArgValue(packagesToScan);
builder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
BeanDefinitionReaderUtils.registerWithGeneratedName(beanDefinition, registry);
}
/**
* Registers {@link ReferenceAnnotationBeanPostProcessor} into {@link BeanFactory}
*
* @param registry {@link BeanDefinitionRegistry}
*/
private void registerReferenceAnnotationBeanPostProcessor(BeanDefinitionRegistry registry) {
// Register @Reference Annotation Bean Processor
// 注册一个ReferenceAnnotationBeanPostProcessor做为bean，ReferenceAnnotationBeanPostProcessor是一个BeanPostProcessor
BeanRegistrar.registerInfrastructureBean(registry,
ReferenceAnnotationBeanPostProcessor.BEAN_NAME, ReferenceAnnotationBeanPostProcessor.class);
}
//省略...
}
```
#### ServiceAnnotationBeanPostProcessor
> 主要就是处理@Service注解
<img src="https://npm.elemecdn.com/youthlql@1.0.4/rpc/dubbo/v1/04_di_si_jie/@Service注解处理流程.png"/>
ServiceAnnotationBeanPostProcessor是一个BeanDefinitionRegistryPostProcessor，是用来注册BeanDefinition的。这个类的名字起的不太好。
它的主要作用是扫描Dubbo的@Service注解，一旦扫描到某个@Service注解就把它以及被它注解的类当做一个Dubbo服务，进行**服务导出**。
##### DubboClassPathBeanDefinitionScanner
DubboClassPathBeanDefinitionScanner是所Dubbo自定义的扫描器，继承了Spring中的ClassPathBeanDefinitionScanner了。
DubboClassPathBeanDefinitionScanner相对于ClassPathBeanDefinitionScanner并没有做太多的改变，只是把useDefaultFilters设置为了false，主要是因为Dubbo中的@Service注解是Dubbo自定义的，在这个注解上并没有用@Component注解（因为Dubbo不是一定要结合Spring才能用），所以为了能利用Spring的扫描逻辑，需要把useDefaultFilters设置为false。
每扫描到一个@Service注解，就会得到一个BeanDefinition，这个BeanDefinition的beanClass属性就是具体的服务实现类。
但，如果仅仅只是这样，这只是得到了一个Spring中的Bean，对于Dubbo来说此时得到的Bean是一个**服务**，并且，还需要解析@Service注解的配置信息，因为这些都是服务的参数信息，所以在扫描完了之后，会针对所得到的每个BeanDefinition，都会**额外**的再生成一个**ServiceBean**类型的Bean对象。
##### ServiceBean
ServiceBean表示一个Dubbo服务，它有一些参数，比如：
1. **ref，表示服务的具体实现类**
2. **interface，表示服务的接口**
3. **parameters，表示服务的参数（@Service注解中所配置的信息）**
4. **application，表示服务所属的应用**
5. **protocols，表示服务所使用的协议**
6. **registries，表示服务所要注册的注册中心**
**所以在扫描到一个@Service注解后，其实会得到两个Bean:**
1. 一个就是服务实现类本身一个Bean对象
2. 一个就是对应的ServiceBean类型的一个Bean对象
并且需要注意的是，ServiceBean实现了ApplicationListener接口，所以当Spring启动完成后会触发onApplicationEvent()方法的调用，而在这个方法内会调用**export()**，这个方法就是**服务导出的入口方法**。
> 关于RuntimeBeanReference参考[https://www.yuque.com/renyong-jmovm/ufz328/gbwvk7](https://www.yuque.com/renyong-jmovm/ufz328/gbwvk7)。
##### 代码注释
> 部分代码注释
```java
/**
* {@link Service} Annotation
* {@link BeanDefinitionRegistryPostProcessor Bean Definition Registry Post Processor}
*
* @since 2.5.8
*/
public class ServiceAnnotationBeanPostProcessor implements BeanDefinitionRegistryPostProcessor, EnvironmentAware,
ResourceLoaderAware, BeanClassLoaderAware {
private final Logger logger = LoggerFactory.getLogger(getClass());
private final Set<String> packagesToScan;
private Environment environment;
private ResourceLoader resourceLoader;
private ClassLoader classLoader;
public ServiceAnnotationBeanPostProcessor(String... packagesToScan) {
this(Arrays.asList(packagesToScan));
}
public ServiceAnnotationBeanPostProcessor(Collection<String> packagesToScan) {
this(new LinkedHashSet<>(packagesToScan));
}
public ServiceAnnotationBeanPostProcessor(Set<String> packagesToScan) {
this.packagesToScan = packagesToScan;
}
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
Set<String> resolvedPackagesToScan = resolvePackagesToScan(packagesToScan);
if (!CollectionUtils.isEmpty(resolvedPackagesToScan)) {
// 扫描包，进行Bean注册
registerServiceBeans(resolvedPackagesToScan, registry);
} else {
if (logger.isWarnEnabled()) {
logger.warn("packagesToScan is empty , ServiceBean registry will be ignored!");
}
}
}
/**
* Registers Beans whose classes was annotated {@link Service}
*
* @param packagesToScan The base packages to scan
* @param registry {@link BeanDefinitionRegistry}
*/
private void registerServiceBeans(Set<String> packagesToScan, BeanDefinitionRegistry registry) {
DubboClassPathBeanDefinitionScanner scanner =
new DubboClassPathBeanDefinitionScanner(registry, environment, resourceLoader);
BeanNameGenerator beanNameGenerator = resolveBeanNameGenerator(registry);
scanner.setBeanNameGenerator(beanNameGenerator);
// 扫描被Service注解标注的类，先成为Spring里的bean，也就是dubbo服务的实现类
scanner.addIncludeFilter(new AnnotationTypeFilter(Service.class));
/**
* Add the compatibility for legacy Dubbo's @Service
*
* The issue : https://github.com/apache/dubbo/issues/4330
* @since 2.7.3
*/
scanner.addIncludeFilter(new AnnotationTypeFilter(com.alibaba.dubbo.config.annotation.Service.class));
for (String packageToScan : packagesToScan) {
// Registers @Service Bean first
// 扫描Dubbo自定义的@Service注解
scanner.scan(packageToScan);
// 查找被@Service注解的类的BeanDefinition（无论这个类有没有被@ComponentScan注解标注了）
// Finds all BeanDefinitionHolders of @Service whether @ComponentScan scans or not.
// beanDefinitionHolders装的就是dubbo服务的实现类，存在了Spring容器里
Set<BeanDefinitionHolder> beanDefinitionHolders =
findServiceBeanDefinitionHolders(scanner, packageToScan, registry, beanNameGenerator);
if (!CollectionUtils.isEmpty(beanDefinitionHolders)) {
// 扫描到BeanDefinition开始处理它，准备生成ServiceBean
for (BeanDefinitionHolder beanDefinitionHolder : beanDefinitionHolders) {
registerServiceBean(beanDefinitionHolder, registry, scanner);
}
if (logger.isInfoEnabled()) {
logger.info(beanDefinitionHolders.size() + " annotated Dubbo's @Service Components { " +
beanDefinitionHolders +
" } were scanned under package[" + packageToScan + "]");
}
} else {
if (logger.isWarnEnabled()) {
logger.warn("No Spring Bean annotating Dubbo's @Service was found under package["
+ packageToScan + "]");
}
}
}
}
/**
* Registers {@link ServiceBean} from new annotated {@link Service} {@link BeanDefinition}
*
* @param beanDefinitionHolder
* @param registry
* @param scanner
* @see ServiceBean
* @see BeanDefinition
*/
private void registerServiceBean(BeanDefinitionHolder beanDefinitionHolder, BeanDefinitionRegistry registry,
DubboClassPathBeanDefinitionScanner scanner) {
// 服务实现类
Class<?> beanClass = resolveClass(beanDefinitionHolder);
// @Service注解
Annotation service = findServiceAnnotation(beanClass);
/**
* The {@link AnnotationAttributes} of @Service annotation
*/
// @Service注解上的信息
AnnotationAttributes serviceAnnotationAttributes = getAnnotationAttributes(service, false, false);
// 服务实现类对应的接口
Class<?> interfaceClass = resolveServiceInterfaceClass(serviceAnnotationAttributes, beanClass);
// 服务实现类对应的bean的名字，比如：demoServiceImpl
String annotatedServiceBeanName = beanDefinitionHolder.getBeanName();
// 生成一个ServiceBean
AbstractBeanDefinition serviceBeanDefinition =
buildServiceBeanDefinition(service, serviceAnnotationAttributes, interfaceClass, annotatedServiceBeanName);
// ServiceBean Bean name
String beanName = generateServiceBeanName(serviceAnnotationAttributes, interfaceClass);
if (scanner.checkCandidate(beanName, serviceBeanDefinition)) { // check duplicated candidate bean
// 把ServiceBean注册进去，对应的beanName为ServiceBean:org.apache.dubbo.demo.DemoService
registry.registerBeanDefinition(beanName, serviceBeanDefinition);
if (logger.isInfoEnabled()) {
logger.info("The BeanDefinition[" + serviceBeanDefinition +
"] of ServiceBean has been registered with name : " + beanName);
}
} else {
if (logger.isWarnEnabled()) {
logger.warn("The Duplicated BeanDefinition[" + serviceBeanDefinition +
"] of ServiceBean[ bean name : " + beanName +
"] was be found , Did @DubboComponentScan scan to same package in many times?");
}
}
}
/**
* Generates the bean name of {@link ServiceBean}
*
* @param serviceAnnotationAttributes
* @param interfaceClass the class of interface annotated {@link Service}
* @return ServiceBean@interfaceClassName#annotatedServiceBeanName
* @since 2.7.3
*/
private String generateServiceBeanName(AnnotationAttributes serviceAnnotationAttributes, Class<?> interfaceClass) {
ServiceBeanNameBuilder builder = create(interfaceClass, environment)
.group(serviceAnnotationAttributes.getString("group"))
.version(serviceAnnotationAttributes.getString("version"));
return builder.build();
}
/**
* Build the {@link AbstractBeanDefinition Bean Definition}
*
* @param serviceAnnotation
* @param serviceAnnotationAttributes
* @param interfaceClass
* @param annotatedServiceBeanName
* @return
* @since 2.7.3
*/
private AbstractBeanDefinition buildServiceBeanDefinition(Annotation serviceAnnotation,
AnnotationAttributes serviceAnnotationAttributes,
Class<?> interfaceClass,
String annotatedServiceBeanName) {
// 生成一个ServiceBean对应的BeanDefinition
BeanDefinitionBuilder builder = rootBeanDefinition(ServiceBean.class);
AbstractBeanDefinition beanDefinition = builder.getBeanDefinition();
MutablePropertyValues propertyValues = beanDefinition.getPropertyValues();
/*
1.先忽略这些比较特殊的属性，为什么要忽略呢？
2.其它不忽略的属性，在@Service注解上写的是字符串形式，ServiceBean里也是字符串类型，所以可以直接赋值
3.下面的这些特殊属性，比如protocol，在注解上写的是@Service(protocol="p1")这样的字符串，但是在ServiceBean里
对应的是ProtocolConfig类型的属性，不可能把字符串赋值给这类型。所以先忽略，后面可以看到单独处理了
*/
String[] ignoreAttributeNames = of("provider", "monitor", "application", "module", "registry", "protocol",
"interface", "interfaceName", "parameters");
// 把@Service注解中的参数值赋值给ServiceBean的属性
propertyValues.addPropertyValues(new AnnotationPropertyValuesAdapter(serviceAnnotation, environment, ignoreAttributeNames));
// References "ref" property to annotated-@Service Bean
// ref属性赋值为另外一个bean, 对应的就是被@Service注解的服务实现类对应的bean
addPropertyReference(builder, "ref", annotatedServiceBeanName);
// Set interface
builder.addPropertyValue("interface", interfaceClass.getName());
// Convert parameters into map
builder.addPropertyValue("parameters", convertParameters(serviceAnnotationAttributes.getStringArray("parameters")));
// 配置了methods属性，则给ServiceBean对应的methods属性赋值
// Add methods parameters
List<MethodConfig> methodConfigs = convertMethodConfigs(serviceAnnotationAttributes.get("methods"));
if (!methodConfigs.isEmpty()) {
builder.addPropertyValue("methods", methodConfigs);
}
/**
* Add {@link org.apache.dubbo.config.ProviderConfig} Bean reference
*/
String providerConfigBeanName = serviceAnnotationAttributes.getString("provider");
if (StringUtils.hasText(providerConfigBeanName)) {
addPropertyReference(builder, "provider", providerConfigBeanName);
}
/**
* Add {@link org.apache.dubbo.config.MonitorConfig} Bean reference
*/
String monitorConfigBeanName = serviceAnnotationAttributes.getString("monitor");
if (StringUtils.hasText(monitorConfigBeanName)) {
addPropertyReference(builder, "monitor", monitorConfigBeanName);
}
/**
* Add {@link org.apache.dubbo.config.ApplicationConfig} Bean reference
*/
String applicationConfigBeanName = serviceAnnotationAttributes.getString("application");
if (StringUtils.hasText(applicationConfigBeanName)) {
addPropertyReference(builder, "application", applicationConfigBeanName);
}
/**
* Add {@link org.apache.dubbo.config.ModuleConfig} Bean reference
*/
String moduleConfigBeanName = serviceAnnotationAttributes.getString("module");
if (StringUtils.hasText(moduleConfigBeanName)) {
addPropertyReference(builder, "module", moduleConfigBeanName);
}
/**
* Add {@link org.apache.dubbo.config.RegistryConfig} Bean reference
* 获取注解上配置的注册中心的beanName
*/
String[] registryConfigBeanNames = serviceAnnotationAttributes.getStringArray("registry");
List<RuntimeBeanReference> registryRuntimeBeanReferences = toRuntimeBeanReferences(registryConfigBeanNames);
if (!registryRuntimeBeanReferences.isEmpty()) {
builder.addPropertyValue("registries", registryRuntimeBeanReferences);
}
/**
* Add {@link org.apache.dubbo.config.ProtocolConfig} Bean reference
*/
String[] protocolConfigBeanNames = serviceAnnotationAttributes.getStringArray("protocol");
List<RuntimeBeanReference> protocolRuntimeBeanReferences = toRuntimeBeanReferences(protocolConfigBeanNames);
if (!protocolRuntimeBeanReferences.isEmpty()) {
builder.addPropertyValue("protocols", protocolRuntimeBeanReferences);
}
return builder.getBeanDefinition();
}
}
```
#### ReferenceAnnotationBeanPostProcessor
> 处理@Reference注解
<img src="https://npm.elemecdn.com/youthlql@1.0.4/rpc/dubbo/v1/04_di_si_jie/@Reference注解处理流程.png"/>
##### 总结
ReferenceAnnotationBeanPostProcessor是处理@Reference注解的。
ReferenceAnnotationBeanPostProcessor的父类是AnnotationInjectedBeanPostProcessor，是一个InstantiationAwareBeanPostProcessorAdapter，是一个BeanPostProcessor。
Spring在对Bean进行依赖注入时会调用AnnotationInjectedBeanPostProcessor的postProcessPropertyValues()方法来给某个Bean按照ReferenceAnnotationBeanPostProcessor的逻辑进行依赖注入。
在注入之前会查找注入点，被@Reference注解的属性或方法都是注入点。
针对某个Bean找到所有注入点之后，就会进行注入了，注入就是给属性或给set方法赋值，但是在赋值之前得先得到一个值，此时就会调用ReferenceAnnotationBeanPostProcessor的**doGetInjectedBean()**方法来得到一个对象，而这个对象的构造就比较复杂了，因为对于Dubbo来说，注入给某个属性的应该是当前这个**属性所对应的服务接口的代理对象**。
但是在生成这个代理对象之前，还要考虑问题：
1. 当前所需要引入的这个服务，是不是在本地就存在(就是当前项目)？不存在则要把按Dubbo的逻辑生成一个代理对象
2. 当前所需要引入的这个服务，是不是已经被引入过了（是不是已经生成过代理对象了），如果是应该是不用再重复去生成了。
**首先如何判断当前所引入的服务是本地的一个服务（就是当前应用自己所提供的服务）。**
我们前面提到，Dubbo通过@Service来提供一个服务，并且会生成两个Bean：
1. 一个服务实现类本身Bean
2. 一个ServiceBean类型的Bean，这个Bean的名字是这么生成的：
```java
private String generateServiceBeanName(AnnotationAttributes serviceAnnotationAttributes, Class<?> interfaceClass) {
ServiceBeanNameBuilder builder = create(interfaceClass, environment)
.group(serviceAnnotationAttributes.getString("group"))
.version(serviceAnnotationAttributes.getString("version"));
return builder.build();
}
```
是通过接口类型+group+version来作为ServiceBean类型Bean的名字的。
```java
ServiceBean:org.apache.dubbo.demo.DemoService:group:version
```
所以现在对于服务引入，也应该提前根据@Reference注解中的信息和属性接口类型去判断一下当前Spring容器中是否存在对应的ServiceBean对象，如果存在则直接取出ServiceBean对象的ref属性所对应的对象，作为要注入的结果。
**然后如何判断当前所引入的这个服务是否已经被引入过了****（是不是已经生成过代理对象了）。**
这就需要在第一次引入某个服务后（生成代理对象后）进行缓存（记录一下）。Dubbo中是这么做的:
1. 首先根据@Reference注解的所有信息+属性接口类型生成一个**字符串**
2. 然后@Reference注解的所有信息+属性接口类型生成一个ReferenceBean对象（**ReferenceBean对象中的get方法可以得到一个Dubbo生成的代理对象，可以理解为服务引入的入口方法**）
3. 把字符串作为beanName，ReferenceBean对象作为bean注册到Spring容器中，同时也会放入**referenceBeanCache**中。
有了这些逻辑，@Reference注解服务引入的过程是这样的：
1. 得到当前所引入服务对应的ServiceBean的beanName（源码中叫referencedBeanName）
2. 根据@Reference注解的所有信息+属性接口类型得到一个referenceBeanName
3. 根据referenceBeanName从**referenceBeanCach**e获取对应的ReferenceBean，如果没有则创建一个ReferenceBean
4. 根据referencedBeanName（ServiceBean的beanName）判断Spring容器中是否存在该bean，如果存在则给ref属性所对应的bean取一个别名，别名为referenceBeanName。
1. 如果Spring容器中不存在referencedBeanName对应的bean，则判断容器中是否存在referenceBeanName所对应的Bean，如果不存在则将创建出来的ReferenceBean注册到Spring容器中（**此处这么做就支持了可以通过@Autowired注解也可以使用服务了，****ReferenceBean是一个FactoryBean**）
5. 如果referencedBeanName存在对应的Bean，则额外生成一个代理对象，代理对象的InvocationHandler会缓存在**localReferenceBeanInvocationHandlerCache中，这样如果引入的是同一个服务，并且这个服务在本地，**
6. 如果referencedBeanName不存在对应的Bean，则直接调用ReferenceBean的get()方法得到一个代理对象
##### AnnotationInjectedBeanPostProcessor代码注释
> 这个类是Spring的类
```java
public AnnotationInjectedBeanPostProcessor(Class<? extends Annotation>... annotationTypes) {
Assert.notEmpty(annotationTypes, "The argument of annotations' types must not empty");
this.annotationTypes = annotationTypes;
}
@Override
public PropertyValues postProcessPropertyValues(
PropertyValues pvs, PropertyDescriptor[] pds, Object bean, String beanName) throws BeanCreationException {
// 寻找需要注入的属性（被@Reference标注的Field），也就是寻找注入点
InjectionMetadata metadata = findInjectionMetadata(beanName, bean.getClass(), pvs);
try {
metadata.inject(bean, beanName, pvs);
} catch (BeanCreationException ex) {
throw ex;
} catch (Throwable ex) {
throw new BeanCreationException(beanName, "Injection of @" + getAnnotationType().getSimpleName()
+ " dependencies is failed", ex);
}
return pvs;
}
private InjectionMetadata findInjectionMetadata(String beanName, Class<?> clazz, PropertyValues pvs) {
// Fall back to class name as cache key, for backwards compatibility with custom callers.
String cacheKey = (StringUtils.hasLength(beanName) ? beanName : clazz.getName());
// Quick check on the concurrent map first, with minimal locking.
AnnotationInjectedBeanPostProcessor.AnnotatedInjectionMetadata metadata = this.injectionMetadataCache.get(cacheKey);
if (InjectionMetadata.needsRefresh(metadata, clazz)) {
synchronized (this.injectionMetadataCache) {
metadata = this.injectionMetadataCache.get(cacheKey);
if (InjectionMetadata.needsRefresh(metadata, clazz)) {
if (metadata != null) {
metadata.clear(pvs);
}
try {
metadata = buildAnnotatedMetadata(clazz);
this.injectionMetadataCache.put(cacheKey, metadata);
} catch (NoClassDefFoundError err) {
throw new IllegalStateException("Failed to introspect object class [" + clazz.getName() +
"] for annotation metadata: could not find class that it depends on", err);
}
}
}
}
return metadata;
}
private AnnotationInjectedBeanPostProcessor.AnnotatedInjectionMetadata buildAnnotatedMetadata(final Class<?> beanClass) {
// 哪些Filed上有@Reference注解
Collection<AnnotationInjectedBeanPostProcessor.AnnotatedFieldElement> fieldElements = findFieldAnnotationMetadata(beanClass);
// 哪些方法上有@Reference注解
Collection<AnnotationInjectedBeanPostProcessor.AnnotatedMethodElement> methodElements = findAnnotatedMethodMetadata(beanClass);
// 返回的是Dubbo定义的AnnotatedInjectionMetadata，接下来就会使用这个类去进行属性注入
return new AnnotationInjectedBeanPostProcessor.AnnotatedInjectionMetadata(beanClass, fieldElements, methodElements);
}
/**
* {@link Annotation Annotated} {@link InjectionMetadata} implementation
*/
private class AnnotatedInjectionMetadata extends InjectionMetadata {
private final Collection<AnnotationInjectedBeanPostProcessor.AnnotatedFieldElement> fieldElements;
private final Collection<AnnotationInjectedBeanPostProcessor.AnnotatedMethodElement> methodElements;
public AnnotatedInjectionMetadata(Class<?> targetClass, Collection<AnnotationInjectedBeanPostProcessor.AnnotatedFieldElement> fieldElements,
Collection<AnnotationInjectedBeanPostProcessor.AnnotatedMethodElement> methodElements) {
super(targetClass, combine(fieldElements, methodElements));
this.fieldElements = fieldElements;
this.methodElements = methodElements;
}
public Collection<AnnotationInjectedBeanPostProcessor.AnnotatedFieldElement> getFieldElements() {
return fieldElements;
}
public Collection<AnnotationInjectedBeanPostProcessor.AnnotatedMethodElement> getMethodElements() {
return methodElements;
}
}
/**
* {@link Annotation Annotated} {@link Method} {@link InjectionMetadata.InjectedElement}
*/
private class AnnotatedMethodElement extends InjectionMetadata.InjectedElement {
private final Method method;
private final AnnotationAttributes attributes;
private volatile Object object;
protected AnnotatedMethodElement(Method method, PropertyDescriptor pd, AnnotationAttributes attributes) {
super(method, pd);
this.method = method;
this.attributes = attributes;
}
@Override
protected void inject(Object bean, String beanName, PropertyValues pvs) throws Throwable {
// set方法对应的属性的类型
Class<?> injectedType = pd.getPropertyType();
// 从Spring容器中获取一个Bean（注意，这个方法内部会生成Bean而且会缓存，就像Spring中的getBean一样）
Object injectedObject = getInjectedObject(attributes, bean, beanName, injectedType, this);
ReflectionUtils.makeAccessible(method);
// 调用set方法
method.invoke(bean, injectedObject);
}
}
/**
* {@link Annotation Annotated} {@link Field} {@link InjectionMetadata.InjectedElement}
*/
public class AnnotatedFieldElement extends InjectionMetadata.InjectedElement {
private final Field field;
private final AnnotationAttributes attributes;
private volatile Object bean;
protected AnnotatedFieldElement(Field field, AnnotationAttributes attributes) {
super(field, null);
this.field = field;
this.attributes = attributes;
}
@Override
protected void inject(Object bean, String beanName, PropertyValues pvs) throws Throwable {
// 给bean对象进行属性赋值
Class<?> injectedType = field.getType();
// 获取对象，然后进行注入
Object injectedObject = getInjectedObject(attributes, bean, beanName, injectedType, this);
ReflectionUtils.makeAccessible(field);
// 字段赋值，injectedObject就是值
field.set(bean, injectedObject);
}
}
protected Object getInjectedObject(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType,
InjectionMetadata.InjectedElement injectedElement) throws Exception {
// ServiceBean:org.apache.dubbo.demo.DemoService#source=private org.apache.dubbo.demo.DemoService org.apache.dubbo.demo.consumer.comp.DemoServiceComponent.demoService#attributes={parameters=[Ljava.lang.String;@42e25b0b}
// 哪个Service应用了哪个类型的服务，通过什么方式引入的
// cacheKey很鸡肋，属性名不一样的时候，cacheKey不一样，导致不能缓存， 在一个Service中@Reference两次同一个服务缓存不到
String cacheKey = buildInjectedObjectCacheKey(attributes, bean, beanName, injectedType, injectedElement);
Object injectedObject = injectedObjectsCache.get(cacheKey);
if (injectedObject == null) {
// // 这里会调用子类的方法生成Bean，这里的子类指的就是ReferenceAnnotationBeanPostProcessor
injectedObject = doGetInjectedBean(attributes, bean, beanName, injectedType, injectedElement);
// Customized inject-object if necessary
injectedObjectsCache.putIfAbsent(cacheKey, injectedObject);
}
return injectedObject;
}
```
##### ReferenceAnnotationBeanPostProcessor代码注释
> 部分注释
```java
/**
* {@link org.springframework.beans.factory.config.BeanPostProcessor} implementation
* that Consumer service {@link Reference} annotated fields
*
* @since 2.5.7
*/
public class ReferenceAnnotationBeanPostProcessor extends AnnotationInjectedBeanPostProcessor implements
ApplicationContextAware, ApplicationListener {
/**
* The bean name of {@link ReferenceAnnotationBeanPostProcessor}
*/
public static final String BEAN_NAME = "referenceAnnotationBeanPostProcessor";
/**
* Cache size
*/
private static final int CACHE_SIZE = Integer.getInteger(BEAN_NAME + ".cache.size", 32);
private final ConcurrentMap<String, ReferenceBean<?>> referenceBeanCache =
new ConcurrentHashMap<>(CACHE_SIZE);
private final ConcurrentHashMap<String, ReferenceBeanInvocationHandler> localReferenceBeanInvocationHandlerCache =
new ConcurrentHashMap<>(CACHE_SIZE);
private final ConcurrentMap<InjectionMetadata.InjectedElement, ReferenceBean<?>> injectedFieldReferenceBeanCache =
new ConcurrentHashMap<>(CACHE_SIZE);
private final ConcurrentMap<InjectionMetadata.InjectedElement, ReferenceBean<?>> injectedMethodReferenceBeanCache =
new ConcurrentHashMap<>(CACHE_SIZE);
private ApplicationContext applicationContext;
/**
* To support the legacy annotation that is @com.alibaba.dubbo.config.annotation.Reference since 2.7.3
*/
public ReferenceAnnotationBeanPostProcessor() {
////调用AnnotationInjectedBeanPostProcessor的构造
super(Reference.class, com.alibaba.dubbo.config.annotation.Reference.class);
}
/**
* Gets all beans of {@link ReferenceBean}
*
* @return non-null read-only {@link Collection}
* @since 2.5.9
*/
public Collection<ReferenceBean<?>> getReferenceBeans() {
return referenceBeanCache.values();
}
/**
* Get {@link ReferenceBean} {@link Map} in injected field.
*
* @return non-null {@link Map}
* @since 2.5.11
*/
public Map<InjectionMetadata.InjectedElement, ReferenceBean<?>> getInjectedFieldReferenceBeanMap() {
return Collections.unmodifiableMap(injectedFieldReferenceBeanCache);
}
/**
* Get {@link ReferenceBean} {@link Map} in injected method.
*
* @return non-null {@link Map}
* @since 2.5.11
*/
public Map<InjectionMetadata.InjectedElement, ReferenceBean<?>> getInjectedMethodReferenceBeanMap() {
return Collections.unmodifiableMap(injectedMethodReferenceBeanCache);
}
// 该方法得到的对象会赋值给@ReferenceBean注解的属性
//
@Override
protected Object doGetInjectedBean(AnnotationAttributes attributes, Object bean, String beanName, Class<?> injectedType,
InjectionMetadata.InjectedElement injectedElement) throws Exception {
// 按ServiceBean的beanName生成规则来生成referencedBeanName， 规则为ServiceBean:interfaceClassName:version:group
String referencedBeanName = buildReferencedBeanName(attributes, injectedType);
/*
1.相当于根据@Reference注解的信息(包括注解括号里的参数)按照toString的逻辑，生成referenceBeanName，这个东西是作为缓存的key
实际上是进行了一些字符串的转换啥的，不用关心
2.注意referencedBeanName和referenceBeanName的区别【一个有d字母，一个没有】。referencedBeanName是ServiceBean的
名字。referenceBeanName是ReferenceBean的名字
*/
String referenceBeanName = getReferenceBeanName(attributes, injectedType);
// 生成一个ReferenceBean对象
ReferenceBean referenceBean = buildReferenceBeanIfAbsent(referenceBeanName, attributes, injectedType);
// 把referenceBean添加到Spring容器中去
registerReferenceBean(referencedBeanName, referenceBean, attributes, injectedType);
//缓存注入点，不重要
cacheInjectedReferenceBean(referenceBean, injectedElement);
// 创建一个代理对象，Service中的属性被注入的就是这个代理对象
// 内部会调用referenceBean.get();
return getOrCreateProxy(referencedBeanName, referenceBeanName, referenceBean, injectedType);
}
/**
* Register an instance of {@link ReferenceBean} as a Spring Bean
*
* @param referencedBeanName The name of bean that annotated Dubbo's {@link Service @Service} in the Spring {@link ApplicationContext}
* @param referenceBean the instance of {@link ReferenceBean} is about to register into the Spring {@link ApplicationContext}
* @param attributes the {@link AnnotationAttributes attributes} of {@link Reference @Reference}
* @param interfaceClass the {@link Class class} of Service interface
* @since 2.7.3
*/
private void registerReferenceBean(String referencedBeanName, ReferenceBean referenceBean,
AnnotationAttributes attributes,
Class<?> interfaceClass) {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
// 就是referenceBeanName
String beanName = getReferenceBeanName(attributes, interfaceClass);
// 当前Spring容器中是否存在referencedBeanName
if (existsServiceBean(referencedBeanName)) { // If @Service bean is local one
/**
* Get the @Service's BeanDefinition from {@link BeanFactory}
* Refer to {@link ServiceAnnotationBeanPostProcessor#buildServiceBeanDefinition}
*/
AbstractBeanDefinition beanDefinition = (AbstractBeanDefinition) beanFactory.getBeanDefinition(referencedBeanName);
RuntimeBeanReference runtimeBeanReference = (RuntimeBeanReference) beanDefinition.getPropertyValues().get("ref"); // ServiceBean --- ref
// The name of bean annotated @Service
String serviceBeanName = runtimeBeanReference.getBeanName(); // DemoServiceImpl对应的beanName
// register Alias rather than a new bean name, in order to reduce duplicated beans
// DemoServiceImpl多了一个别名
beanFactory.registerAlias(serviceBeanName, beanName);
} else { // Remote @Service Bean
if (!beanFactory.containsBean(beanName)) {
/*
1.放入Spring容器里的应该是DemoService的实现类的代理对象，但是这里放的却是referenceBean类型对象
2.referenceBean的父类有个get()可以直接获取到代理对象，那这里为啥不放呢？其实是为了支持@Autowire注解
3.首先ReferenceBean实现了Spring的FactoryBean接口,FactoryBean获取对象时是这样的调用顺序
FactoryBean.getObject() ==> getObject().get() ==>最终调子类ReferenceBean#get()
刚好给@Autowire注解注入了代理对象
*/
beanFactory.registerSingleton(beanName, referenceBean);
}
}
}
/**
* Get the bean name of {@link ReferenceBean} if {@link Reference#id() id attribute} is present,
* or {@link #generateReferenceBeanName(AnnotationAttributes, Class) generate}.
*
* @param attributes the {@link AnnotationAttributes attributes} of {@link Reference @Reference}
* @param interfaceClass the {@link Class class} of Service interface
* @return non-null
* @since 2.7.3
*/
private String getReferenceBeanName(AnnotationAttributes attributes, Class<?> interfaceClass) {
// id attribute appears since 2.7.3
String beanName = getAttribute(attributes, "id");
// beanName为null时会进入if判断
if (!hasText(beanName)) {
beanName = generateReferenceBeanName(attributes, interfaceClass);
}
return beanName;
}
/**
* Build the bean name of {@link ReferenceBean}
*
* @param attributes the {@link AnnotationAttributes attributes} of {@link Reference @Reference}
* @param interfaceClass the {@link Class class} of Service interface
* @return
* @since 2.7.3
*/
private String generateReferenceBeanName(AnnotationAttributes attributes, Class<?> interfaceClass) {
StringBuilder beanNameBuilder = new StringBuilder("@Reference");
if (!attributes.isEmpty()) {
beanNameBuilder.append('(');
for (Map.Entry<String, Object> entry : attributes.entrySet()) {
beanNameBuilder.append(entry.getKey())
.append('=')
.append(entry.getValue())
.append(',');
}
// replace the latest "," to be ")"
beanNameBuilder.setCharAt(beanNameBuilder.lastIndexOf(","), ')');
}
beanNameBuilder.append(" ").append(interfaceClass.getName());
return beanNameBuilder.toString();
}
private boolean existsServiceBean(String referencedBeanName) {
return applicationContext.containsBean(referencedBeanName);
}
/**
* Get or Create a proxy of {@link ReferenceBean} for the specified the type of Dubbo service interface
*
* @param referencedBeanName The name of bean that annotated Dubbo's {@link Service @Service} in the Spring {@link ApplicationContext}
* @param referenceBeanName the bean name of {@link ReferenceBean}
* @param referenceBean the instance of {@link ReferenceBean}
* @param serviceInterfaceType the type of Dubbo service interface
* @return non-null
* @since 2.7.4
*/
private Object getOrCreateProxy(String referencedBeanName, String referenceBeanName, ReferenceBean referenceBean, Class<?> serviceInterfaceType) {
/*
1.引入的服务在Spirng容器里有，说明是本项目的bean，按理来说应该直接把DemoService的实现类赋给@Reference注解标注的属性
2.但实际上不是，@Reference实际上最后赋值的是一个代理对象，因为除开需要执行DemoService的实现类里的方法，@Reference
注解标注的属性还需要实现其它很多逻辑，实现这些增强逻辑之后最终才执行的DemoService的实现类里的方法。如果直接赋值
DemoServiceImpl，那么Dubbo里面的很多逻辑就走不到了
*/
if (existsServiceBean(referencedBeanName)) { // If the local @Service Bean exists, build a proxy of ReferenceBean
//wrapInvocationHandler最后也会调用referenceBean.get()，其实和下面的else一样
return newProxyInstance(getClassLoader(), new Class[]{serviceInterfaceType},
wrapInvocationHandler(referenceBeanName, referenceBean));
} else { // ReferenceBean should be initialized and get immediately
// 重点，最终从这里赋值给@Reference注解标注的属性
return referenceBean.get();
}
}
/**
* Wrap an instance of {@link InvocationHandler} that is used to get the proxy of {@link ReferenceBean} after
* the specified local referenced bean that annotated {@link @Service} exported.
*
* @param referenceBeanName the bean name of {@link ReferenceBean}
* @param referenceBean the instance of {@link ReferenceBean}
* @return non-null
* @since 2.7.4
*/
private InvocationHandler wrapInvocationHandler(String referenceBeanName, ReferenceBean referenceBean) {
return localReferenceBeanInvocationHandlerCache.computeIfAbsent(referenceBeanName, name ->
new ReferenceBeanInvocationHandler(referenceBean));
}
private static class ReferenceBeanInvocationHandler implements InvocationHandler {
private final ReferenceBean referenceBean;
private Object bean;
private ReferenceBeanInvocationHandler(ReferenceBean referenceBean) {
this.referenceBean = referenceBean;
}
@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result;
try {
if (bean == null) { // If the bean is not initialized, invoke init()
// issue: https://github.com/apache/dubbo/issues/3429
init();
}
result = method.invoke(bean, args);
} catch (InvocationTargetException e) {
// re-throws the actual Exception.
throw e.getTargetException();
}
return result;
}
private void init() {
this.bean = referenceBean.get();
}
}
@Override
protected String buildInjectedObjectCacheKey(AnnotationAttributes attributes, Object bean, String beanName,
Class<?> injectedType, InjectionMetadata.InjectedElement injectedElement) {
return buildReferencedBeanName(attributes, injectedType) +
"#source=" + (injectedElement.getMember()) +
"#attributes=" + AnnotationUtils.resolvePlaceholders(attributes, getEnvironment());
}
/**
* @param attributes the attributes of {@link Reference @Reference}
* @param serviceInterfaceType the type of Dubbo's service interface
* @return The name of bean that annotated Dubbo's {@link Service @Service} in local Spring {@link ApplicationContext}
*/
private String buildReferencedBeanName(AnnotationAttributes attributes, Class<?> serviceInterfaceType) {
ServiceBeanNameBuilder serviceBeanNameBuilder = create(attributes, serviceInterfaceType, getEnvironment());
return serviceBeanNameBuilder.build();
}
private ReferenceBean buildReferenceBeanIfAbsent(String referenceBeanName, AnnotationAttributes attributes,
Class<?> referencedType)
throws Exception {
/*
1.key就是@Reference注解最终生成的字符串,value却不是简单的代理对象
2.一个ServiceBean表示一个Dubbo服务，ReferenceBean表示引用的哪个dubbo服务
3.所以ReferenceBean不是简单的代理对象，他保存了诸如超时时间,轮询参数等等这些东西
【和ServcieBean很类似,ServcieBean也保存了这些东西】
4.ReferenceBean的父类ReferenceConfig#get()最终返回代理对象
5.ServiceBean和ReferenceBean思想基本上是一样的
6.ReferenceBean最终会放入缓存，赋值给@Reference注解所标注的属性的依然是代理对象
*/
ReferenceBean<?> referenceBean = referenceBeanCache.get(referenceBeanName);
if (referenceBean == null) {
// 生成了一个ReferenceBean对象，attributes是@Reference注解的参数值
ReferenceBeanBuilder beanBuilder = ReferenceBeanBuilder
.create(attributes, applicationContext)
.interfaceClass(referencedType);
referenceBean = beanBuilder.build();
referenceBeanCache.put(referenceBeanName, referenceBean);
} else if (!referencedType.isAssignableFrom(referenceBean.getInterfaceClass())) {
throw new IllegalArgumentException("reference bean name " + referenceBeanName + " has been duplicated, but interfaceClass " +
referenceBean.getInterfaceClass().getName() + " cannot be assigned to " + referencedType.getName());
}
return referenceBean;
}
private void cacheInjectedReferenceBean(ReferenceBean referenceBean,
InjectionMetadata.InjectedElement injectedElement) {
if (injectedElement.getMember() instanceof Field) {
injectedFieldReferenceBeanCache.put(injectedElement, referenceBean);
} else if (injectedElement.getMember() instanceof Method) {
injectedMethodReferenceBeanCache.put(injectedElement, referenceBean);
}
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.applicationContext = applicationContext;
}
@Override
public void onApplicationEvent(ApplicationEvent event) {
if (event instanceof ServiceBeanExportedEvent) {
onServiceBeanExportEvent((ServiceBeanExportedEvent) event);
} else if (event instanceof ContextRefreshedEvent) {
onContextRefreshedEvent((ContextRefreshedEvent) event);
}
}
private void onServiceBeanExportEvent(ServiceBeanExportedEvent event) {
ServiceBean serviceBean = event.getServiceBean();
initReferenceBeanInvocationHandler(serviceBean);
}
private void initReferenceBeanInvocationHandler(ServiceBean serviceBean) {
String serviceBeanName = serviceBean.getBeanName();
// Remove ServiceBean when it's exported
ReferenceBeanInvocationHandler handler = localReferenceBeanInvocationHandlerCache.remove(serviceBeanName);
// Initialize
if (handler != null) {
handler.init();
}
}
private void onContextRefreshedEvent(ContextRefreshedEvent event) {
}
@Override
public void destroy() throws Exception {
super.destroy();
this.referenceBeanCache.clear();
this.localReferenceBeanInvocationHandlerCache.clear();
this.injectedFieldReferenceBeanCache.clear();
this.injectedMethodReferenceBeanCache.clear();
}
}
```
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