聊聊springboot的ConfigurationProperties的绑定

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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 ConfigurationPropertiesBindingPostProcessorimplements 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;@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext = applicationContext;}@Overridepublic void afterPropertiesSet() throws Exception {// We can't use constructor injection of the application context because// it causes eager factory bean initializationthis.registry = (BeanDefinitionRegistry) this.applicationContext.getAutowireCapableBeanFactory();this.binder = ConfigurationPropertiesBinder.get(this.applicationContext);}@Overridepublic int getOrder() {return Ordered.HIGHEST_PRECEDENCE + 1;}@Overridepublic 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);}}

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<Object> bindTarget = Bindable.of(bindType).withAnnotations(annotations);if (instance != null) {bindTarget = bindTarget.withExistingValue(instance);}return new ConfigurationPropertiesBean(name, instance, annotation, bindTarget);}

get方法主要是获取工厂方法，之后获取annotation，获取bindTarget，最后创建ConfigurationPropertiesBean

ConfigurationPropertiesBean

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

/*** Provides access to {@link ConfigurationProperties @ConfigurationProperties} bean* details, regardless of if the annotation was used directly or on a {@link Bean @Bean}* factory method. This class can be used to access {@link #getAll(ApplicationContext)* all} configuration properties beans in an ApplicationContext, or* {@link #get(ApplicationContext, Object, String) individual beans} on a case-by-case* basis (for example, in a {@link BeanPostProcessor}).** @author Phillip Webb* @since 2.2.0* @see #getAll(ApplicationContext)* @see #get(ApplicationContext, Object, String)*/
public final class ConfigurationPropertiesBean {private final String name;private final Object instance;private final ConfigurationProperties annotation;private final Bindable<?> bindTarget;private final BindMethod bindMethod;//......
}	

ConfigurationPropertiesBean用于代表一个标注了@ConfigurationProperties注解的bean的信息

ConfigurationPropertiesBinder

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

/*** Internal class used by the {@link ConfigurationPropertiesBindingPostProcessor} to* handle the actual {@link ConfigurationProperties @ConfigurationProperties} binding.** @author Stephane Nicoll* @author Phillip Webb*/
class ConfigurationPropertiesBinder {private static final String BEAN_NAME = "org.springframework.boot.context.internalConfigurationPropertiesBinder";private static final String FACTORY_BEAN_NAME = "org.springframework.boot.context.internalConfigurationPropertiesBinderFactory";private static final String VALIDATOR_BEAN_NAME = EnableConfigurationProperties.VALIDATOR_BEAN_NAME;private final ApplicationContext applicationContext;private final PropertySources propertySources;private final Validator configurationPropertiesValidator;private final boolean jsr303Present;private volatile Validator jsr303Validator;private volatile Binder binder;ConfigurationPropertiesBinder(ApplicationContext applicationContext) {this.applicationContext = applicationContext;this.propertySources = new PropertySourcesDeducer(applicationContext).getPropertySources();this.configurationPropertiesValidator = getConfigurationPropertiesValidator(applicationContext);this.jsr303Present = ConfigurationPropertiesJsr303Validator.isJsr303Present(applicationContext);}BindResult<?> bind(ConfigurationPropertiesBean propertiesBean) {Bindable<?> target = propertiesBean.asBindTarget();ConfigurationProperties annotation = propertiesBean.getAnnotation();BindHandler bindHandler = getBindHandler(target, annotation);return getBinder().bind(annotation.prefix(), target, bindHandler);}private Binder getBinder() {if (this.binder == null) {this.binder = new Binder(getConfigurationPropertySources(), getPropertySourcesPlaceholdersResolver(),getConversionService(), getPropertyEditorInitializer(), null,ConfigurationPropertiesBindConstructorProvider.INSTANCE);}return this.binder;}//......
}	

ConfigurationPropertiesBinder的bind方法根据ConfigurationPropertiesBean的target与annotation取获取bindHandler，然后通过binder去执行bind方法
binder的构造器依赖了propertySources、placeholdersResolver、conversionService、propertyEditorInitializer、defaultBindHandler、constructorProvider

Binder

org/springframework/boot/context/properties/bind/Binder.java

	private <T> Object bindObject(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,Context context, boolean allowRecursiveBinding) {ConfigurationProperty property = findProperty(name, context);if (property == null && context.depth != 0 && containsNoDescendantOf(context.getSources(), name)) {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 bindersObject instance = bindDataObject(name, target, handler, context, allowRecursiveBinding);if (instance != null) {return instance;}throw ex;}}return bindDataObject(name, target, handler, context, allowRecursiveBinding);}private AggregateBinder<?> getAggregateBinder(Bindable<?> target, Context context) {Class<?> resolvedType = target.getType().resolve(Object.class);if (Map.class.isAssignableFrom(resolvedType)) {return new MapBinder(context);}if (Collection.class.isAssignableFrom(resolvedType)) {return new CollectionBinder(context);}if (target.getType().isArray()) {return new ArrayBinder(context);}return null;}private <T> Object bindAggregate(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler,Context context, AggregateBinder<?> aggregateBinder) {AggregateElementBinder elementBinder = (itemName, itemTarget, source) -> {boolean allowRecursiveBinding = aggregateBinder.isAllowRecursiveBinding(source);Supplier<?> supplier = () -> bind(itemName, itemTarget, handler, context, allowRecursiveBinding, false);return context.withSource(source, supplier);};return context.withIncreasedDepth(() -> aggregateBinder.bind(name, target, elementBinder));}private <T> Object bindProperty(Bindable<T> target, Context context, ConfigurationProperty property) {context.setConfigurationProperty(property);Object result = property.getValue();result = this.placeholdersResolver.resolvePlaceholders(result);result = context.getConverter().convert(result, target);return result;}

bindObject方法先通过findProperty获取ConfigurationProperty，然后执行bindAggregate或者bindProperty；AggregateBinder主要是处理Map、Collection、Array类型；bindProperty方法这里从property获取绑定的值，然后resolvePlaceholders，最后通过converter的convert方法把值绑定到target上

BindConverter

org/springframework/boot/context/properties/bind/BindConverter.java

	<T> T convert(Object value, ResolvableType type, Annotation... annotations) {if (value == null) {return null;}return (T) this.conversionService.convert(value, TypeDescriptor.forObject(value),new ResolvableTypeDescriptor(type, annotations));}

BindConverter的convert方法则是通过conversionService进行

小结

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