默認效果： ? 1）、瀏覽器，返回一個默認的錯誤頁面  瀏覽器發送請求的請求頭：  ? 2）、如果是其他客戶端，默認響應一個json數據   原理： ? 可以參照ErrorMvcAutoConfiguration；錯誤處理的自動配置； 給容器中添加了以下組件 ? 1、DefaultErrorAttributes： ```java 幫我們在頁面共享信息； @Override public Map<String, Object> getErrorAttributes(RequestAttributes requestAttributes, boolean includeStackTrace) { Map<String, Object> errorAttributes = new LinkedHashMap<String, Object>(); errorAttributes.put("timestamp", new Date()); addStatus(errorAttributes, requestAttributes); addErrorDetails(errorAttributes, requestAttributes, includeStackTrace); addPath(errorAttributes, requestAttributes); return errorAttributes; } ``` ? 2、BasicErrorController：處理默認/error請求 ```java @Controller @RequestMapping("${server.error.path:${error.path:/error}}") public class BasicErrorController extends AbstractErrorController { @RequestMapping(produces = "text/html")//產生html類型的數據；瀏覽器發送的請求來到這個方法處理 public ModelAndView errorHtml(HttpServletRequest request, HttpServletResponse response) { HttpStatus status = getStatus(request); Map<String, Object> model = Collections.unmodifiableMap(getErrorAttributes( request, isIncludeStackTrace(request, MediaType.TEXT_HTML))); response.setStatus(status.value()); //去哪個頁面作為錯誤頁面；包含頁面地址和頁面內容 ModelAndView modelAndView = resolveErrorView(request, response, status, model); return (modelAndView == null ? new ModelAndView("error", model) : modelAndView); } @RequestMapping @ResponseBody //產生json數據，其他客戶端來到這個方法處理； public ResponseEntity<Map<String, Object>> error(HttpServletRequest request) { Map<String, Object> body = getErrorAttributes(request, isIncludeStackTrace(request, MediaType.ALL)); HttpStatus status = getStatus(request); return new ResponseEntity<Map<String, Object>>(body, status); } ``` ? 3、ErrorPageCustomizer： ```java @Value("${error.path:/error}") private String path = "/error"; 系統出現錯誤以后來到error請求進行處理；（web.xml注冊的錯誤頁面規則） ``` ? 4、DefaultErrorViewResolver： ```java @Override public ModelAndView resolveErrorView(HttpServletRequest request, HttpStatus status, Map<String, Object> model) { ModelAndView modelAndView = resolve(String.valueOf(status), model); if (modelAndView == null && SERIES_VIEWS.containsKey(status.series())) { modelAndView = resolve(SERIES_VIEWS.get(status.series()), model); } return modelAndView; } private ModelAndView resolve(String viewName, Map<String, Object> model) { //默認SpringBoot可以去找到一個頁面？ error/404 String errorViewName = "error/" + viewName; //模板引擎可以解析這個頁面地址就用模板引擎解析 TemplateAvailabilityProvider provider = this.templateAvailabilityProviders .getProvider(errorViewName, this.applicationContext); if (provider != null) { //模板引擎可用的情況下返回到errorViewName指定的視圖地址 return new ModelAndView(errorViewName, model); } //模板引擎不可用，就在靜態資源文件夾下找errorViewName對應的頁面 error/404.html return resolveResource(errorViewName, model); } ``` ? 步驟： ? 一但系統出現4xx或者5xx之類的錯誤；ErrorPageCustomizer就會生效（定制錯誤的響應規則）；就會來到/error請求；就會被**BasicErrorController**處理； ? 1）響應頁面；去哪個頁面是由**DefaultErrorViewResolver**解析得到的； ```java protected ModelAndView resolveErrorView(HttpServletRequest request, HttpServletResponse response, HttpStatus status, Map<String, Object> model) { //所有的ErrorViewResolver得到ModelAndView for (ErrorViewResolver resolver : this.errorViewResolvers) { ModelAndView modelAndView = resolver.resolveErrorView(request, status, model); if (modelAndView != null) { return modelAndView; } } return null; } ```