一、編寫實例，只要加上ConfigurationProperties注解，就會從當前springboot的Environment中讀取配置屬笥。Environment包括bootStrap,application,application_dev等。

@Data @Configuration @ConfigurationProperties(prefix = "redisson") public class RedissonProperties {private int timeout = 3000;private String address;private String password;private int database = 0;private int connectionPoolSize = 64;private int connectionMinimumIdleSize=10;private int slaveConnectionPoolSize = 250;private int masterConnectionPoolSize = 250;private String[] sentinelAddresses;private String masterName; }

二、注入流程

1.在SPRING容器實例化BEAN對象后，會觸發

ConfigurationPropertiesBindingPostProcessor.postProcessBeforeInitialization方法，進行屬性值注入。這種跟@resource的依賴注入流程機制是一樣的，都是實現了BeanPostProcessor的后置處理器，進行屬性的修改，或者對象的代理封裝轉換等。 org.springframework.boot.context.properties.ConfigurationPropertiesBindingPostProcessor public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {bind(ConfigurationPropertiesBean.get(this.applicationContext, bean, beanName));return bean;}

?2.隨后會調用ConfigurationPropertiesBean.create方法，判斷BEAN類上是否有ConfigurationProperties注解，有才進行配置文件的屬性注入。

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);}

?

3.真正讀取配置文件屬性并綁定設置到BEAN對象屬性中是由?

ConfigurationPropertiesBinder.bind方法完成。 BindResult<?> bind(ConfigurationPropertiesBean propertiesBean) {Bindable<?> target = propertiesBean.asBindTarget();ConfigurationProperties annotation = propertiesBean.getAnnotation();BindHandler bindHandler = getBindHandler(target, annotation);return getBinder().bind(annotation.prefix(), target, bindHandler);}

4.隨后會調用org.springframework.boot.context.properties.bind.binder.bindDataObject 進行數據對

象綁定。

private Object bindDataObject(ConfigurationPropertyName name, Bindable<?> target, BindHandler handler,Context context, boolean allowRecursiveBinding) {if (isUnbindableBean(name, target, context)) {return null;}Class<?> type = target.getType().resolve(Object.class);if (!allowRecursiveBinding && context.isBindingDataObject(type)) {return null;}DataObjectPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(name.append(propertyName),propertyTarget, handler, context, false, false);return context.withDataObject(type, () -> {for (DataObjectBinder dataObjectBinder : this.dataObjectBinders) {Object instance = dataObjectBinder.bind(name, target, context, propertyBinder);if (instance != null) {return instance;}}return null;});}

5.其中有個JAVA數據對象，會遍歷當前對象的所有屬性，逐個屬性進行讀取配置，進行綁定。

org.springframework.boot.context.properties.bind.JavaBeanBinder private <T> boolean bind(DataObjectPropertyBinder propertyBinder, Bean<T> bean, BeanSupplier<T> beanSupplier,Context context) {boolean bound = false;for (BeanProperty beanProperty : bean.getProperties().values()) {bound |= bind(beanSupplier, propertyBinder, beanProperty);context.clearConfigurationProperty();}return bound;}

6.最終會調用Binder.findProperty進行屬性查找。這里面的context.getSource就是springboot初始化時加載的各類資源配置屬性對象列表。包括系統環境變量，配置文件，JVM參數等。

private ConfigurationProperty findProperty(ConfigurationPropertyName name, Context context) {if (name.isEmpty()) {return null;}for (ConfigurationPropertySource source : context.getSources()) {ConfigurationProperty property = source.getConfigurationProperty(name);if (property != null) {return property;}}return null;}

7.綁定完的屬性注入如下，可以看到配置的屬性已經注入進去。

總結

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