dubbo源码—dubbo自定义spring xml标签

// 类DefaultNamespaceHandlerResolver
public NamespaceHandler resolve(String namespaceUri) {
  // 这里namespaceUri = http://code.alibabatech.com/schema/dubbo
  // 加载所有的handlers配置，并取出dubbo自定义的handler
  Map<String, Object> handlerMappings = getHandlerMappings();
  Object handlerOrClassName = handlerMappings.get(namespaceUri);
  // ... 省略中间代码
  // 实例化handler并缓存起来，然后调用init方法
  NamespaceHandler namespaceHandler = (NamespaceHandler) BeanUtils.instantiateClass(handlerClass);
  namespaceHandler.init();
  handlerMappings.put(namespaceUri, namespaceHandler);
  return namespaceHandler;
  // ... 省略中间代码
}

private Map<String, Object> getHandlerMappings() {
  // ... 省略中间代码
  // 这里handlerMappingsLocation = META-INF/spring.handlers
  // 加在classpath下所有spring.handlers
  Properties mappings =
    PropertiesLoaderUtils.loadAllProperties(this.handlerMappingsLocation, this.classLoader);
  if (logger.isDebugEnabled()) {
    logger.debug("Loaded NamespaceHandler mappings: " + mappings);
  }
  Map<String, Object> handlerMappings = new ConcurrentHashMap<String, Object>(mappings.size());
  CollectionUtils.mergePropertiesIntoMap(mappings, handlerMappings);
  this.handlerMappings = handlerMappings;
  // ... 省略中间代码
}

public void init() {
  // 参数true表示在解析的时候如果没有指定id需要生成一个id
  registerBeanDefinitionParser("application", new DubboBeanDefinitionParser(ApplicationConfig.class, true));
  registerBeanDefinitionParser("module", new DubboBeanDefinitionParser(ModuleConfig.class, true));
  registerBeanDefinitionParser("registry", new DubboBeanDefinitionParser(RegistryConfig.class, true));
  registerBeanDefinitionParser("monitor", new DubboBeanDefinitionParser(MonitorConfig.class, true));
  registerBeanDefinitionParser("provider", new DubboBeanDefinitionParser(ProviderConfig.class, true));
  registerBeanDefinitionParser("consumer", new DubboBeanDefinitionParser(ConsumerConfig.class, true));
  registerBeanDefinitionParser("protocol", new DubboBeanDefinitionParser(ProtocolConfig.class, true));
  registerBeanDefinitionParser("service", new DubboBeanDefinitionParser(ServiceBean.class, true));
  registerBeanDefinitionParser("reference", new DubboBeanDefinitionParser(ReferenceBean.class, false));
  registerBeanDefinitionParser("annotation", new DubboBeanDefinitionParser(AnnotationBean.class, true));
}

private static BeanDefinition parse(Element element, ParserContext parserContext, Class<?> beanClass, boolean required) {
  RootBeanDefinition beanDefinition = new RootBeanDefinition();
  beanDefinition.setBeanClass(beanClass);
  beanDefinition.setLazyInit(false);
  String id = element.getAttribute("id");
  if ((id == null || id.length() == 0) && required) {
    // 如果没有配置id，先依次试图获取name、interface作为generatedBeanName
    if (generatedBeanName == null || generatedBeanName.length() == 0) {
      // 如果上面的属性都没有配置则直接获取class的全名作为id
      generatedBeanName = beanClass.getName();
    }
    // 以防该class有其他的实例（比如可以配置多协议，dubbo:protocol），在后面加上一个数字加以区分
    id = generatedBeanName; 
    int counter = 2;
    while(parserContext.getRegistry().containsBeanDefinition(id)) {
      id = generatedBeanName + (counter ++);
    }
  }
  if (id != null && id.length() > 0) {
    // double check
    if (parserContext.getRegistry().containsBeanDefinition(id))  {
      throw new IllegalStateException("Duplicate spring bean id " + id);
    }
    // 将BeanDefinition注册到容器
    parserContext.getRegistry().registerBeanDefinition(id, beanDefinition);
    beanDefinition.getPropertyValues().addPropertyValue("id", id);
  }
  if (ProtocolConfig.class.equals(beanClass)) {
    // ... 省略中间代码
    // 如果是ProtocolConfig，会找出容器中所有配置了protocol属性的bean，并设置为RuntimeBeanReference
    definition.getPropertyValues().addPropertyValue("protocol", new RuntimeBeanReference(id));
  } else if (ServiceBean.class.equals(beanClass)) {
    // ... 省略中间代码
    // 如果dubbo:service配置class属性，将ref属性设置为class属性对应的bean
    beanDefinition.getPropertyValues().addPropertyValue("ref", new BeanDefinitionHolder(classDefinition, id + "Impl"));
  } else if (ProviderConfig.class.equals(beanClass)) {
    // 解析dubbo:provider包含的子标签
    parseNested(element, parserContext, ServiceBean.class, true, "service", "provider", id, beanDefinition);
  } else if (ConsumerConfig.class.equals(beanClass)) {
    // 解析dubbo:consumer包含的子标签
    parseNested(element, parserContext, ReferenceBean.class, false, "reference", "consumer", id, beanDefinition);
  }
  // ... 省略中间代码
  // 下面的代码就是解析bean属性(比如：parameters、registry等)添加到beanDefinition中
}