1错误处理的自动配置

ErrorMvcAutoConfiguration

步骤：

1 一但系统出现4xx或者5xx之类的错误，ErrorPageCustomizer就会生效（定制错误的响应规则）

相当于发生错误后，返回/error请求，这里会重定向
private static class ErrorPageCustomizer implements ErrorPageRegistrar, Ordered {

   private final ServerProperties properties;

   private final DispatcherServletPath dispatcherServletPath;

   protected ErrorPageCustomizer(ServerProperties properties,
         DispatcherServletPath dispatcherServletPath) {
      this.properties = properties;
      this.dispatcherServletPath = dispatcherServletPath;
   }

   @Override
   public void registerErrorPages(ErrorPageRegistry errorPageRegistry) {
      ErrorPage errorPage = new ErrorPage(this.dispatcherServletPath
            .getRelativePath(this.properties.getError().getPath()));//返回的是/error
      errorPageRegistry.addErrorPages(errorPage);
   }

   @Override
   public int getOrder() {
      return 0;
   }
}

2 就会发生/error请求

3 就会被BasicErrorController处理。

@Bean
@ConditionalOnMissingBean(value = ErrorController.class, search = SearchStrategy.CURRENT)
public BasicErrorController basicErrorController(ErrorAttributes errorAttributes) {
   return new BasicErrorController(errorAttributes, this.serverProperties.getError(),
         this.errorViewResolvers);
}

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

@RequestMapping(produces = MediaType.TEXT_HTML_VALUE)//处理浏览器的错误,返回html
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());
//去错误页面设置
   ModelAndView modelAndView = resolveErrorView(request, response, status, model);
   return (modelAndView != null) ? modelAndView : new ModelAndView("error", model);
}

@RequestMapping //处理客户端错误，返回json
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<>(body, status);
}

4 DefaultErrorViewResolver决定去哪个页面

public class DefaultErrorViewResolver implements ErrorViewResolver, Ordered {

   private static final Map<Series, String> SERIES_VIEWS;

   static {

      Map<Series, String> views = new EnumMap<>(Series.class);
//处理4开头的状态码
      views.put(Series.CLIENT_ERROR, "4xx");
      views.put(Series.SERVER_ERROR, "5xx");
      SERIES_VIEWS = Collections.unmodifiableMap(views);
   }

决定去哪个页面
private ModelAndView resolve(String viewName, Map<String, Object> model) {
   String errorViewName = "error/" + viewName;
   TemplateAvailabilityProvider provider = this.templateAvailabilityProviders
         .getProvider(errorViewName, this.applicationContext);
   if (provider != null) {
      return new ModelAndView(errorViewName, model);
   }
   return resolveResource(errorViewName, model);
}

private ModelAndView resolveResource(String viewName, Map<String, Object> model) {
   for (String location : this.resourceProperties.getStaticLocations()) {
      try {
         Resource resource = this.applicationContext.getResource(location);
         resource = resource.createRelative(viewName + ".html");
         if (resource.exists()) {
            return new ModelAndView(new HtmlResourceView(resource), model);
         }
      }
      catch (Exception ex) {
      }
   }
   return null;
}

什么代码决定有模板引擎情况下,会去/error下状态码对应的页面。

如果没有模板引擎就去找静态资源文件夹下状态码对应的页面

如果没有状态码对应的错误页面，就去系统提供的默认页面

2定制错误响应

1相应都是json数据

测试代码

@ControllerAdvice
public class MyExceptionHandler {
    //1、浏览器客户端返回的都是json
    @ResponseBody
    @ExceptionHandler(Exception.class)
    public Map<String,Object> handleException(Exception e){
        Map<String,Object> map = new HashMap<>();
        map.put("code","500");
        map.put("message","500错误");
        return map;
    }


}


@Controller
public class HelloController {


    @RequestMapping("/hello")
    public  void hello(){
        throw new RuntimeException("RuntimeException");
    }
}

2根据客户端和浏览器来返回不同的方式

@ControllerAdvice
public class MyExceptionHandler {


    @ExceptionHandler(Exception.class)
    public String handleException(Exception e, HttpServletRequest request){
        Map<String,Object> map = new HashMap<>();

        //设置错误状态码
        request.setAttribute("javax.servlet.error.status_code",520);
        map.put("code","520");
        map.put("message","520错误");

        request.setAttribute("ext",map);
        //转发到/error,那里会到浏览器和客户端情况分别进行设置
        return "forward:/error";
    }
}

图中一个是5xx页面

3定制返回数据

在原有基础上添加类

//给容器中加入我们自己定义的ErrorAttributes
@Component
public class MyErrorAttributes extends DefaultErrorAttributes {
    @Override
    //返回值的map就是页面和json能获取的所有字段
    public Map<String, Object> getErrorAttributes(WebRequest webRequest, boolean includeStackTrace) {

         Map<String, Object> map = super.getErrorAttributes(webRequest, includeStackTrace);
        map.put("message1","message1");
        map.put("message2","message2");
        map.put("message3","message3");

        //我们的异常处理器携带的数据
        Map<String,Object> ext = (Map<String, Object>) webRequest.getAttribute("ext", 0);
        map.put("ext",ext);
        return map;

    }

 
}

sprint-boot错误处理+错误处理的自动配置+定制错误响应

1错误处理的自动配置

2定制错误响应

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