聊聊springboot的ConfigurationProperties的绑定

序

本文主要研究一下springboot的ConfigurationProperties的绑定

ConfigurationPropertiesBindingPostProcessor

org/springframework/boot/context/properties/ConfigurationPropertiesBindingPostProcessor.java

/**
 * {@link BeanPostProcessor} to bind {@link PropertySources} to beans annotated with
 * {@link ConfigurationProperties @ConfigurationProperties}.
 *
 * @author Dave Syer
 * @author Phillip Webb
 * @author Christian Dupuis
 * @author Stephane Nicoll
 * @author Madhura Bhave
 * @since 1.0.0
 */
public class ConfigurationPropertiesBindingPostProcessor
		implements BeanPostProcessor, PriorityOrdered, ApplicationContextAware, InitializingBean {

	/**
	 * The bean name that this post-processor is registered with.
	 */
	public static final String BEAN_NAME = ConfigurationPropertiesBindingPostProcessor.class.getName();

	private ApplicationContext applicationContext;

	private BeanDefinitionRegistry registry;

	private ConfigurationPropertiesBinder binder;

	@Override
	public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		this.applicationContext = applicationContext;
	}

	@Override
	public void afterPropertiesSet() throws Exception {
		// We can't use constructor injection of the application context because
		// it causes eager factory bean initialization
		this.registry = (BeanDefinitionRegistry) this.applicationContext.getAutowireCapableBeanFactory();
		this.binder = ConfigurationPropertiesBinder.get(this.applicationContext);
	}

	@Override
	public int getOrder() {
		return Ordered.HIGHEST_PRECEDENCE + 1;
	}

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

	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 {
			this.binder.bind(bean);
		}
		catch (Exception ex) {
			throw new ConfigurationPropertiesBindException(bean, ex);
		}
	}

	private boolean hasBoundValueObject(String beanName) {
		return this.registry.containsBeanDefinition(beanName) && this.registry
				.getBeanDefinition(beanName) instanceof ConfigurationPropertiesValueObjectBeanDefinition;
	}

	/**
	 * Register a {@link ConfigurationPropertiesBindingPostProcessor} bean if one is not
	 * already registered.
	 * @param registry the bean definition registry
	 * @since 2.2.0
	 */
	public static void register(BeanDefinitionRegistry registry) {
		Assert.notNull(registry, "Registry must not be null");
		if (!registry.containsBeanDefinition(BEAN_NAME)) {
			BeanDefinition definition = BeanDefinitionBuilder
					.genericBeanDefinition(ConfigurationPropertiesBindingPostProcessor.class,
							ConfigurationPropertiesBindingPostProcessor::new)
					.getBeanDefinition();
			definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
			registry.registerBeanDefinition(BEAN_NAME, definition);
		}
		ConfigurationPropertiesBinder.register(registry);
	}

}
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ConfigurationPropertiesBindingPostProcessor实现了BeanPostProcessor、PriorityOrdered、ApplicationContextAware、InitializingBean四个接口；其getOrder方法返回的是Ordered.HIGHEST_PRECEDENCE + 1即仅次于最高的优先级；其postProcessBeforeInitialization方法主要是执行bind方法(先通过ConfigurationPropertiesBean.get获取ConfigurationPropertiesBean，再通过binder进行bind)；其afterPropertiesSet主要是获取BeanDefinitionRegistry与ConfigurationPropertiesBinder

ConfigurationPropertiesBean.get

org/springframework/boot/context/properties/ConfigurationPropertiesBean.java

	public static ConfigurationPropertiesBean get(ApplicationContext applicationContext, Object bean, String beanName) {
		Method factoryMethod = findFactoryMethod(applicationContext, beanName);
		return create(beanName, bean, bean.getClass(), factoryMethod);
	}

	private static ConfigurationPropertiesBean create(String name, Object instance, Class type, Method factory) {
		ConfigurationProperties annotation = findAnnotation(instance, type, factory, ConfigurationProperties.class);
		if (annotation == null) {
			return null;
		}
		Validated validated = findAnnotation(instance, type, factory, Validated.class);
		Annotation[] annotations = (validated != null) ? new Annotation[] { annotation, validated }
				: new Annotation[] { annotation };
		ResolvableType bindType = (factory != null) ? ResolvableType.forMethodReturnType(factory)
				: ResolvableType.forClass(type);
		Bindable