Shulou(Shulou.com)06/02 Report--

This article mainly introduces how to use SpringFramework's ControllerAdvice annotations, which has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

SpringFramework version of 5.0.9.release.

We handle exceptions through @ ControllerAdvice and @ ExceptionHandler. How does Springmvc handle them?

ControllerAdviceBean has an important method findAnnotatedBeans, such as List-1

List-1

Public class ControllerAdviceBean implements Ordered {... Public static List findAnnotatedBeans (ApplicationContext applicationContext) {List beans = new ArrayList (); String [] var2 = BeanFactoryUtils.beanNamesForTypeIncludingAncestors (applicationContext, Object.class); int var3 = var2.length; for (int var4 = 0; var4)

< var3; ++var4) { String name = var2[var4]; if (applicationContext.findAnnotationOnBean(name, ControllerAdvice.class) != null) { beans.add(new ControllerAdviceBean(name, applicationContext)); } } return beans; } ... 如List-1所示，从applicationContext中获取所有的ControllerAdvice注解的Bean，之后封装到ControllerAdviceBean中。 来看下ExceptionHandlerExceptionResolver，它的类继承图如下图1所示: 图1 ExceptionHandlerExceptionResolver是HandlerExceptionResolver，所以在Springmvc的doDispatch中会调用它。实现了InitializingBean，所以有afterPropertiesSet方法，如下List-2所示: List-2 @Overridepublic void afterPropertiesSet() { // Do this first, it may add ResponseBodyAdvice beans initExceptionHandlerAdviceCache(); ...}private void initExceptionHandlerAdviceCache() { ... List adviceBeans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext()); AnnotationAwareOrderComparator.sort(adviceBeans); for (ControllerAdviceBean adviceBean : adviceBeans) { Class beanType = adviceBean.getBeanType(); if (beanType == null) { throw new IllegalStateException("Unresolvable type for ControllerAdviceBean: " + adviceBean); } ExceptionHandlerMethodResolver resolver = new ExceptionHandlerMethodResolver(beanType); if (resolver.hasExceptionMappings()) { this.exceptionHandlerAdviceCache.put(adviceBean, resolver); if (logger.isInfoEnabled()) { logger.info("Detected @ExceptionHandler methods in " + adviceBean); } } if (ResponseBodyAdvice.class.isAssignableFrom(beanType)) { this.responseBodyAdvice.add(adviceBean); if (logger.isInfoEnabled()) { logger.info("Detected ResponseBodyAdvice implementation in " + adviceBean); } } }} List-2中，initExceptionHandlerAdviceCache方法调用List-1中ControllerAdviceBean的findAnnotatedBeans方法，获取所有ControllerAdvice的bean，之后排序，所以当有多个ControllerAdivce注解的类且需要排序时，可以实现spring的Order接口来实现。 之后遍历ControllerAdviceBean，之后获取Bean的class类，传入到ExceptionHandlerMethodResolver的构造方法中，如下List-3所示: List-3 public class ExceptionHandlerMethodResolver { ... public static final MethodFilter EXCEPTION_HANDLER_METHODS = method ->

(AnnotationUtils.findAnnotation (method, ExceptionHandler.class)! = null); Private final Map

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.