SpringBoot-27 异常自动配置ErrorMvcAutoConfiguration

默认规则

• 默认情况下，Spring Boot提供/error处理所有错误的映射
• 对于机器客户端，它将生成JSON响应，其中包含错误，HTTP状态和异常消息的详细信息。对于浏览器客户端，响应一个“ whitelabel”错误视图，以HTML格式呈现相同的数据

By default, Spring Boot provides an /error mapping that handles all errors in a sensible way, and it
is registered as a “global” error page in the servlet container. For machine clients, it produces a
JSON response with details of the error, the HTTP status, and the exception message. For browser
clients, there is a “whitelabel” error view that renders the same data in HTML format (to customize
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it, add a View that resolves to error).

• 要对其进行自定义，添加View解析为error

• 要完全替换默认行为，可以实现 ErrorController 并注册该类型的Bean定义，或添加ErrorAttributes类型的组件以使用现有机制但替换其内容。
• error/下的4xx，5xx页面会被自动解析；

3、异常处理自动配置原理

3.1 ErrorMvcAutoConfiguration  自动配置异常处理规则

3.1.1 配置属性：@EnableConfigurationProperties({ ServerProperties.class, WebMvcProperties.class })

• ServerProperties--->errorproperties--->private String path = "/error";

3.1.2 容器组件：类型：DefaultErrorAttributes -> id：errorAttributes

    @Bean
    @ConditionalOnMissingBean(value = ErrorAttributes.class, search = SearchStrategy.CURRENT)
    public DefaultErrorAttributes errorAttributes() {
        return new DefaultErrorAttributes();
    }

• public class DefaultErrorAttributes implements ErrorAttributes, HandlerExceptionResolver, Ordered
• DefaultErrorAttributes：定义错误页面中可以包含哪些数据

•     public Map<String, Object> getErrorAttributes(WebRequest webRequest, ErrorAttributeOptions options) {
          Map<String, Object> errorAttributes = getErrorAttributes(webRequest, options.isIncluded(Include.STACK_TRACE));
          if (Boolean.TRUE.equals(this.includeException)) {
              options = options.including(Include.EXCEPTION);
          }
          if (!options.isIncluded(Include.EXCEPTION)) {
              errorAttributes.remove("exception");
          }
          if (!options.isIncluded(Include.STACK_TRACE)) {
              errorAttributes.remove("trace");
          }
          if (!options.isIncluded(Include.MESSAGE) && errorAttributes.get("message") != null) {
              errorAttributes.put("message", "");
          }
          if (!options.isIncluded(Include.BINDING_ERRORS)) {
              errorAttributes.remove("errors");
          }
          return errorAttributes;
      }

• @Override
      @Deprecated
      public Map<String, Object> getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {
          Map<String, Object> errorAttributes = new LinkedHashMap<>();
          errorAttributes.put("timestamp", new Date());
          addStatus(errorAttributes, webRequest);
          addErrorDetails(errorAttributes, webRequest, includeStackTrace);
          addPath(errorAttributes, webRequest);
          return errorAttributes;
      }
  
      private void addStatus(Map<String, Object> errorAttributes, RequestAttributes requestAttributes) {
          Integer status = getAttribute(requestAttributes, RequestDispatcher.ERROR_STATUS_CODE);
          if (status == null) {
              errorAttributes.put("status", 999);
              errorAttributes.put("error", "None");
              return;
          }
          errorAttributes.put("status", status);
          try {
              errorAttributes.put("error", HttpStatus.valueOf(status).getReasonPhrase());
          }
          catch (Exception ex) {
              // Unable to obtain a reason
              errorAttributes.put("error", "Http Status " + status);
          }
      }

3.1.3容器中的组件：类型：BasicErrorController --> id：basicErrorController（json+白页 适配响应）

@RequestMapping("${server.error.path:${error.path:/error}}")
public class BasicErrorController extends AbstractErrorController{}

• 是一个Controller
• 类上注解：@RequestMapping("${server.error.path:${error.path:/error}}")

• 处理默认 /error 路径的请求；
• 页面响应 new ModelAndView("error", model)；
• 容器中有组件 View->id是error；（响应默认错误页）
• 容器中放组件 BeanNameViewResolver（视图解析器）；按照返回的视图名作为组件的id去容器中找View对象。

3.1.4 容器中的组件：类型：DefaultErrorViewResolver -> id：conventionErrorViewResolver

• 如果发生错误，会以HTTP的状态码 作为视图页地址（viewName），找到真正的页面
• error/404、5xx.html

 如果想要返回页面；就会找error视图【StaticView】。(默认是一个白页)

SpringBoot-27 异常自动配置ErrorMvcAutoConfiguration

原文：https://www.cnblogs.com/fengyupinglan/p/14587341.html