spring 面试题

1.springboot自动装配

从 这个META-INF/spring-autoconfigure-metadata.properties加载文件

2.springbean 的生命周期

3.spring 如何解绝循环依赖

private final Map<String, Object> earlySingletonObjects = new ConcurrentHashMap<>(16);
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);

synchronized (this.singletonObjects) {
			Object singletonObject = this.singletonObjects.get(beanName);
			if (singletonObject == null) {
				beforeSingletonCreation(beanName);
				try {
					singletonObject = singletonFactory.getObject();
					newSingleton = true;
				}
				catch (IllegalStateException ex) {
					singletonObject = this.singletonObjects.get(beanName);

				}
				finally {
					afterSingletonCreation(beanName);
				}
				if (newSingleton) {
					addSingleton(beanName, singletonObject);
				}
			}
			return singletonObject;
		}

4. spring cloud zuul 的类型

 forward SendForwardFilter，SimpleHostRoutingFilter

 pre   PreDecorationFilter，FormBodyWrapperFilter，DebugFilter

 post   LocationRewriteFilter，SendErrorFilter，SendResponseFilter

5.spring cloud 的 eureka 的负载保护