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本文次要钻研一下 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);
}
}ConfigurationPropertiesBindingPostProcessor 实现了 BeanPostProcessor、PriorityOrdered、ApplicationContextAware、InitializingBean 四个接口；其 getOrder 办法返回的是
Ordered.HIGHEST_PRECEDENCE + 1即仅次于最高的优先级；其 postProcessBeforeInitialization 办法次要是执行 bind 办法 (先通过 ConfigurationPropertiesBean.get 获取 ConfigurationPropertiesBean，再通过 binder 进行 bind)；其 afterPropertiesSet 次要是获取 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 办法次要是获取工厂办法，之后获取 annotation，获取 bindTarget，最初创立 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 办法依据 ConfigurationPropertiesBean 的 target 与 annotation 取获取 bindHandler，而后通过 binder 去执行 bind 办法
binder 的结构器依赖了 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 binders
Object 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 办法先通过 findProperty 获取 ConfigurationProperty，而后执行 bindAggregate 或者 bindProperty；AggregateBinder 次要是解决 Map、Collection、Array 类型；bindProperty 办法这里从 property 获取绑定的值，而后 resolvePlaceholders，最初通过 converter 的 convert 办法把值绑定到 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 办法则是通过 conversionService 进行
小结
ConfigurationPropertiesBindingPostProcessor 实现了 BeanPostProcessor、PriorityOrdered、ApplicationContextAware、InitializingBean 四个接口；其 getOrder 办法返回的是 Ordered.HIGHEST_PRECEDENCE + 1 即仅次于最高的优先级；其 postProcessBeforeInitialization 办法次要是执行 bind 办法 ( 先通过 ConfigurationPropertiesBean.get 获取 ConfigurationPropertiesBean，再通过 binder 进行 bind)；其 afterPropertiesSet 次要是获取 BeanDefinitionRegistry 与 ConfigurationPropertiesBinder