spring boot 异常处理扩展(返回格式protofuf)
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2022-07-12 18:31:54
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spring boot 提供了统一的异常处理机制,@ControllerAdvice, @ExceptionHandler两个注解,可以处理controller里抛出的异常,不要对每个controller方法进行try catch,如果你使用json或者返回固定的错误页面作为传输数据格式,普通的使用方法即可解决,由于我们服务端使用protobuf与客户端进行交互,每个controller方法的返回类型的泛型都是不固定的,于是做了一定的扩展,以适应每个controller的返回:
/** * 全局异常处理 * Created by mxl on 2016/9/2. */ @ControllerAdvice public class GlobalExceptionHandler { private static volatile Map<String, HandlerMapping> matchingBeans = null; private static volatile ApplicationContext context = null; private Logger logger = LoggerFactory.getLogger(GlobalExceptionHandler.class); /** * 获取map * @return */ public static Map<String, HandlerMapping> getMatchingBeans (HttpServletRequest request) { if (matchingBeans != null) { return matchingBeans; } synchronized (GlobalExceptionHandler.class) { if (matchingBeans == null) { ApplicationContext context = getContext(request); matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false); } return matchingBeans; } } /** * 获取context * @param request * @return */ public static ApplicationContext getContext (HttpServletRequest request) { if (context != null) { return context; } synchronized (GlobalExceptionHandler.class) { if (context == null) { context = WebApplicationContextUtils.getRequiredWebApplicationContext(request.getServletContext()); } return context; } } @ExceptionHandler(value = GenericException.class) public ResponseEntity<?> GenericExceptionHandler(HttpServletRequest request, GenericException genericException) { try { HandlerMethod handlerMethod = null; //根据request请求解析出目标方法 Map<String, HandlerMapping> matchingBeans = getMatchingBeans(request); for (HandlerMapping hm : matchingBeans.values()) { HandlerExecutionChain handler = hm.getHandler(request); if (handler != null) { handlerMethod = (HandlerMethod)handler.getHandler(); break; } } //根据目标方法,根据反射,获取controller方法返回的protobuf对应的builder,并填装固定的异常返回格式 MessageOrBuilder builder = getBuilder(getReturnType(handlerMethod)); if (builder == null) { return null; } return createResult(builder, genericException); } catch (Exception ee) { ee.printStackTrace(); } return null; } @ExceptionHandler(value = Exception.class) public ResponseEntity<?> defaultErrorHandler(HttpServletRequest request, Exception e) throws Exception { try { HandlerMethod handlerMethod = null; //根据request请求解析出目标方法 Map<String, HandlerMapping> matchingBeans = getMatchingBeans(request); for (HandlerMapping hm : matchingBeans.values()) { HandlerExecutionChain handler = hm.getHandler(request); if (handler != null) { handlerMethod = (HandlerMethod)handler.getHandler(); break; } } //根据目标方法,根据反射,获取controller方法返回的protobuf对应的builder,并填装固定的异常返回格式 MessageOrBuilder builder = getBuilder(getReturnType(handlerMethod)); return createResult(builder, new OperateFailureException("系统异常", Constants.Code.SERVER_ERROR)); } catch (Exception ee) { ee.printStackTrace(); logger.error(ee.getMessage()); } return null; } //利用反射获取填充builder private ResponseEntity<?> createResult (MessageOrBuilder messageOrBuilder, GenericException e) { try { Method successMethod = messageOrBuilder.getClass().getDeclaredMethod("setSuccess", boolean.class); successMethod.invoke(messageOrBuilder, false); Method msgMethod = messageOrBuilder.getClass().getDeclaredMethod("setMsg", String.class); msgMethod.invoke(messageOrBuilder, e.getMessage()); Method codeMethod = messageOrBuilder.getClass().getDeclaredMethod("setCode", int.class); codeMethod.invoke(messageOrBuilder, e.getErrorCode()); Method builderMethod = messageOrBuilder.getClass().getDeclaredMethod("build"); return ResponseEntity.ok(builderMethod.invoke(messageOrBuilder)); } catch (Exception ee) { e.printStackTrace(); logger.error(ee.getMessage()); } return null; } /** * 获取builder * @param returnType * @return */ public static MessageOrBuilder getBuilder (Type returnType) { try { Class returnClass = Class.forName(returnType.getTypeName()); Method builderMethod = returnClass.getDeclaredMethod("newBuilder"); return (MessageOrBuilder)builderMethod.invoke(returnClass); } catch (Exception e) { e.printStackTrace(); } return null; } /** * 返回类型 * @param handlerMethod * @return */ public static Type getReturnType (HandlerMethod handlerMethod) { Type type = handlerMethod.getMethod().getAnnotatedReturnType().getType(); if (type instanceof ParameterizedType)/* 如果是泛型类型 */{ Type[] types = ((ParameterizedType) type) .getActualTypeArguments();// 泛型类型列表 return types[0]; } return null; } }
我们controller里是这样做返回的:
@RequestMapping(value = "creative/list", method = RequestMethod.POST) public ResponseEntity<FeedResponse> listCreative(RequestEntity<FeedRequest> requestEntity) { FeedResponse.Builder builder = FeedResponse.newBuilder(); FeedRequest feed = requestEntity.getBody(); PaginationParam paginationParam = new PaginationParam(feed.getStartCount(), feed.getMaxCount() + 1); SortParam sortParam; if (feed.hasOrderColumn() && feed.hasSort()) { sortParam = PagiSortUtils.createSortParam(feed.getOrderColumn(), feed.getSort()); } else { sortParam = new SortParam("update_time", "desc"); } List<Creative> creativeList = creativeService.findByUser(feed.getUid(), sortParam, paginationParam, PubStatus.DELETE.value); builder.addAllDataList( convertCreativeFeedList(creativeList.subList(0, Math.min(creativeList.size(), feed.getMaxCount())), true, null)); builder.setSuccess(true).setCode(Constants.Code.OK).setHasMore(creativeList.size() > feed.getMaxCount()); return ResponseEntity.ok(builder.build()); }
扩展的具体思路是, 异常捕捉方法中暴露了两个参数request, exception,扩展点在于如何获取每个controller方法返回值的泛型,以创建具体的protobuf返回到客户端, spring boot有一个SimpleMappingExceptionResolver可以扩展,重新此方法, 此方法暴露了HandlerMethod,但是返回格式固定为ModelAndView了,不符合我们的要求;使用主机的方式,去解析request,获取目标方法handlerMethod, 然后利用反射获取目标方法的返回值类型,然后创建返回值类型,做出返回值构建,返回
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