SpringBoot ConfigurationProperties

 * @see ConfigurationPropertiesScan
 * @see ConstructorBinding
 * @see ConfigurationPropertiesBindingPostProcessor
 * @see EnableConfigurationProperties

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Import(ConfigurationPropertiesScanRegistrar.class)
@EnableConfigurationProperties
public @interface ConfigurationPropertiesScan {}

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

	@Override
	public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
	    // 注册bean
		registerInfrastructureBeans(registry);
	  // 配置属性Bean注册器
		ConfigurationPropertiesBeanRegistrar beanRegistrar = new ConfigurationPropertiesBeanRegistrar(registry);
		// 循环注册
		getTypes(metadata).forEach(beanRegistrar::register);
	}

	static void registerInfrastructureBeans(BeanDefinitionRegistry registry) {
	    // 属性绑定后置处理器
		ConfigurationPropertiesBindingPostProcessor.register(registry);
		// 属性校验器
		ConfigurationPropertiesBeanDefinitionValidator.register(registry);
		ConfigurationBeanFactoryMetadata.register(registry);
	}

	public static void register(BeanDefinitionRegistry registry) {
		Assert.notNull(registry, "Registry must not be null");
		// 是否存在
		if (!registry.containsBeanDefinition(BEAN_NAME)) {
			GenericBeanDefinition definition = new GenericBeanDefinition();
			definition.setBeanClass(ConfigurationPropertiesBindingPostProcessor.class);
			definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
			registry.registerBeanDefinition(BEAN_NAME, definition);
		}
		ConfigurationPropertiesBinder.register(registry);
	}

	static void register(BeanDefinitionRegistry registry) {
		Assert.notNull(registry, "Registry must not be null");
		if (!registry.containsBeanDefinition(BEAN_NAME)) {
			GenericBeanDefinition definition = new GenericBeanDefinition();
			definition.setBeanClass(ConfigurationPropertiesBeanDefinitionValidator.class);
			definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
			registry.registerBeanDefinition(BEAN_NAME, definition);
		}
		ConfigurationPropertiesBinder.register(registry);
	}

    /**
     * 找出 {@link EnableConfigurationProperties} 注解标记的中的属性值,并且返回值不是void
     * @param metadata
     * @return
     */
	private Set<Class<?>> getTypes(AnnotationMetadata metadata) {
		return

		 metadata.getAnnotations().stream(EnableConfigurationProperties.class)
				.flatMap((annotation) -> Arrays.stream(annotation.getClassArray(MergedAnnotation.VALUE)))
				.filter((type) -> void.class != type).collect(Collectors.toSet());
	}

	void register(Class<?> type) {
		MergedAnnotation<ConfigurationProperties> annotation = MergedAnnotations
				.from(type, SearchStrategy.TYPE_HIERARCHY).get(ConfigurationProperties.class);
		register(type, annotation);
	}

	@Override
	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
		// 绑定
		bind(ConfigurationPropertiesBean.get(this.applicationContext, bean, beanName));
		return bean;
	}

	private static Method findFactoryMethod(ConfigurableListableBeanFactory beanFactory, String beanName) {
		// 判断是否存在这个beanName
		if (beanFactory.containsBeanDefinition(beanName)) {
		    // 获取bean定义
			BeanDefinition beanDefinition = beanFactory.getMergedBeanDefinition(beanName);
			// 类型判断
			if (beanDefinition instanceof RootBeanDefinition) {
			    // 解析方法
				Method resolvedFactoryMethod = ((RootBeanDefinition) beanDefinition).getResolvedFactoryMethod();
				if (resolvedFactoryMethod != null) {
					return resolvedFactoryMethod;
				}
			}
			return findFactoryMethodUsingReflection(beanFactory, beanDefinition);
		}
		return null;
	}

	private static Method findFactoryMethodUsingReflection(ConfigurableListableBeanFactory beanFactory,
			BeanDefinition beanDefinition) {
		// 工厂方法
		String factoryMethodName = beanDefinition.getFactoryMethodName();
		// 工厂bean
		String factoryBeanName = beanDefinition.getFactoryBeanName();
		if (factoryMethodName == null || factoryBeanName == null) {
			return null;
		}
		// 转换对象
		Class<?> factoryType = beanFactory.getType(factoryBeanName);
		if (factoryType.getName().contains(ClassUtils.CGLIB_CLASS_SEPARATOR)) {
			factoryType = factoryType.getSuperclass();
		}
		AtomicReference<Method> factoryMethod = new AtomicReference<>();
		ReflectionUtils.doWithMethods(factoryType, (method) -> {
			  // 判断是否是需要的方法
		    if (method.getName().equals(factoryMethodName)) {
				// 设置方法
				factoryMethod.set(method);
			}
		});
		// 返回方法
		return factoryMethod.get();
	}

	private static ConfigurationPropertiesBean create(String name, Object instance, Class<?> type, Method factory) {
		// 找注解
		ConfigurationProperties annotation = findAnnotation(instance, type, factory, ConfigurationProperties.class);
		if (annotation == null) {
			return null;
		}
		// 找注解
		Validated validated = findAnnotation(instance, type, factory, Validated.class);
		// 注解列表
		Annotation[] annotations = (validated != null) ? new Annotation[] { annotation, validated }
				: new Annotation[] { annotation };
		// 类型解析
		ResolvableType bindType = (factory != null) ? ResolvableType.forMethodReturnType(factory)
				: ResolvableType.forClass(type);
		// 绑定结果对象
		Bindable<Object> bindTarget = Bindable.of(bindType).withAnnotations(annotations);
		if (instance != null) {
			bindTarget = bindTarget.withExistingValue(instance);
		}
		return new ConfigurationPropertiesBean(name, instance, annotation, bindTarget);
	}

server:
  port: 9999

	private void bind(ConfigurationPropertiesBean bean) {
		if (bean == null || hasBoundValueObject(bean.getName())) {
			return;
		}
		Assert.state(bean.getBindMethod() == BindMethod.JAVA_BEAN, "Cannot bind @ConfigurationProperties for bean '"
				+ bean.getName() + "'. Ensure that @ConstructorBinding has not been applied to regular bean");
		try {
			// 最终的绑定
			this.binder.bind(bean);
		}
		catch (Exception ex) {
			throw new ConfigurationPropertiesBindException(bean, ex);
		}
	}

BindResult<?> bind(ConfigurationPropertiesBean propertiesBean) {
	    // 最后的结果
		Bindable<?> target = propertiesBean.asBindTarget();
		// 注解获取
		ConfigurationProperties annotation = propertiesBean.getAnnotation();
		// 获取处理器
		BindHandler bindHandler = getBindHandler(target, annotation);
		//
		return getBinder().bind(annotation.prefix(), target, bindHandler);
	}

	private ConfigurationProperty findProperty(ConfigurationPropertyName name, Context context) {
		if (name.isEmpty()) {
			return null;
		}
		for (ConfigurationPropertySource source : context.getSources()) {
		    // 获取具体的一个属性值
			ConfigurationProperty property = source.getConfigurationProperty(name);
			if (property != null) {
				return property;
			}
		}
		return null;
	}

private <T> BindHandler getBindHandler(Bindable<T> target, ConfigurationProperties annotation) {
		// 获取校验接口列表
		List<Validator> validators = getValidators(target);
		// 处理器
		BindHandler handler = new IgnoreTopLevelConverterNotFoundBindHandler();
		if (annotation.ignoreInvalidFields()) {
			// 忽略错误的绑定处理器
			handler = new IgnoreErrorsBindHandler(handler);
		}
		if (!annotation.ignoreUnknownFields()) {
			UnboundElementsSourceFilter filter = new UnboundElementsSourceFilter();
			// 未绑定元素处理器
			handler = new NoUnboundElementsBindHandler(handler, filter);
		}
		if (!validators.isEmpty()) {
			// 校验绑定处理器
			handler = new ValidationBindHandler(handler, validators.toArray(new Validator[0]));
		}
		for (ConfigurationPropertiesBindHandlerAdvisor advisor : getBindHandlerAdvisors()) {
			// handler
			handler = advisor.apply(handler);
		}
		return handler;
	}

	private <T> Object bindObject(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,
			Context context, boolean allowRecursiveBinding) {
	    // 获取属性
		ConfigurationProperty property = findProperty(name, context);
		if (property == null && containsNoDescendantOf(context.getSources(), name) && context.depth != 0) {
			return null;
		}
		AggregateBinder<?> aggregateBinder = getAggregateBinder(target, context);
		if (aggregateBinder != null) {
			return bindAggregate(name, target, handler, context, aggregateBinder);
		}
		if (property != null) {
			try {
				return bindProperty(target, context, property);
			}
			catch (ConverterNotFoundException ex) {
				// We might still be able to bind it using the recursive binders
				Object instance = bindDataObject(name, target, handler, context, allowRecursiveBinding);
				if (instance != null) {
					return instance;
				}
				throw ex;
			}
		}
		return bindDataObject(name, target, handler, context, allowRecursiveBinding);
	}