spring boot中ErrorWebFluxAutoConfiguration的作用是什么
spring boot中ErrorWebFluxAutoConfiguration的作用是什么，相信很多没有经验的人对此束手无策，为此本文总结了问题出现的原因和解决方法，通过这篇文章希望你能解决这个问题。
ErrorWebFluxAutoConfiguration
spring-boot-autoconfigure-2.1.5.RELEASE-sources.jar!/org/springframework/boot/autoconfigure/web/reactive/error/ErrorWebFluxAutoConfiguration.java
@Configuration@ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)@ConditionalOnClass(WebFluxConfigurer.class)@AutoConfigureBefore(WebFluxAutoConfiguration.class)@EnableConfigurationProperties({ ServerProperties.class, ResourceProperties.class })public class ErrorWebFluxAutoConfiguration { private final ServerProperties serverProperties; private final ApplicationContext applicationContext; private final ResourceProperties resourceProperties; private final List viewResolvers; private final ServerCodecConfigurer serverCodecConfigurer; public ErrorWebFluxAutoConfiguration(ServerProperties serverProperties, ResourceProperties resourceProperties, ObjectProvider viewResolversProvider, ServerCodecConfigurer serverCodecConfigurer, ApplicationContext applicationContext) { this.serverProperties = serverProperties; this.applicationContext = applicationContext; this.resourceProperties = resourceProperties; this.viewResolvers = viewResolversProvider.orderedStream() .collect(Collectors.toList()); this.serverCodecConfigurer = serverCodecConfigurer; } @Bean @ConditionalOnMissingBean(value = ErrorWebExceptionHandler.class, search = SearchStrategy.CURRENT) @Order(-1) public ErrorWebExceptionHandler errorWebExceptionHandler( ErrorAttributes errorAttributes) { DefaultErrorWebExceptionHandler exceptionHandler = new DefaultErrorWebExceptionHandler( errorAttributes, this.resourceProperties, this.serverProperties.getError(), this.applicationContext); exceptionHandler.setViewResolvers(this.viewResolvers); exceptionHandler.setMessageWriters(this.serverCodecConfigurer.getWriters()); exceptionHandler.setMessageReaders(this.serverCodecConfigurer.getReaders()); return exceptionHandler; } @Bean @ConditionalOnMissingBean(value = ErrorAttributes.class, search = SearchStrategy.CURRENT) public DefaultErrorAttributes errorAttributes() { return new DefaultErrorAttributes( this.serverProperties.getError().isIncludeException()); }} ErrorWebFluxAutoConfiguration注册了DefaultErrorAttributes、ErrorWebExceptionHandler
ErrorAttributes
spring-boot-2.1.5.RELEASE-sources.jar!/org/springframework/boot/web/reactive/error/ErrorAttributes.java
public interface ErrorAttributes { /** * Return a {@link Map} of the error attributes. The map can be used as the model of * an error page, or returned as a {@link ServerResponse} body. * @param request the source request * @param includeStackTrace if stack trace elements should be included * @return a map of error attributes */ Map getErrorAttributes(ServerRequest request, boolean includeStackTrace); /** * Return the underlying cause of the error or {@code null} if the error cannot be * extracted. * @param request the source ServerRequest * @return the {@link Exception} that caused the error or {@code null} */ Throwable getError(ServerRequest request); /** * Store the given error information in the current {@link ServerWebExchange}. * @param error the {@link Exception} that caused the error * @param exchange the source exchange */ void storeErrorInformation(Throwable error, ServerWebExchange exchange);} ErrorAttributes接口定义了getErrorAttributes、getError、storeErrorInformation三个方法
DefaultErrorAttributes
spring-boot-2.1.5.RELEASE-sources.jar!/org/springframework/boot/web/reactive/error/DefaultErrorAttributes.java
public class DefaultErrorAttributes implements ErrorAttributes { private static final String ERROR_ATTRIBUTE = DefaultErrorAttributes.class.getName() + ".ERROR"; private final boolean includeException; /** * Create a new {@link DefaultErrorAttributes} instance that does not include the * "exception" attribute. */ public DefaultErrorAttributes() { this(false); } /** * Create a new {@link DefaultErrorAttributes} instance. * @param includeException whether to include the "exception" attribute */ public DefaultErrorAttributes(boolean includeException) { this.includeException = includeException; } @Override public Map getErrorAttributes(ServerRequest request, boolean includeStackTrace) { Map errorAttributes = new LinkedHashMap<>(); errorAttributes.put("timestamp", new Date()); errorAttributes.put("path", request.path()); Throwable error = getError(request); HttpStatus errorStatus = determineHttpStatus(error); errorAttributes.put("status", errorStatus.value()); errorAttributes.put("error", errorStatus.getReasonPhrase()); errorAttributes.put("message", determineMessage(error)); handleException(errorAttributes, determineException(error), includeStackTrace); return errorAttributes; } private HttpStatus determineHttpStatus(Throwable error) { if (error instanceof ResponseStatusException) { return ((ResponseStatusException) error).getStatus(); } ResponseStatus responseStatus = AnnotatedElementUtils .findMergedAnnotation(error.getClass(), ResponseStatus.class); if (responseStatus != null) { return responseStatus.code(); } return HttpStatus.INTERNAL_SERVER_ERROR; } private String determineMessage(Throwable error) { if (error instanceof WebExchangeBindException) { return error.getMessage(); } if (error instanceof ResponseStatusException) { return ((ResponseStatusException) error).getReason(); } ResponseStatus responseStatus = AnnotatedElementUtils .findMergedAnnotation(error.getClass(), ResponseStatus.class); if (responseStatus != null) { return responseStatus.reason(); } return error.getMessage(); } private Throwable determineException(Throwable error) { if (error instanceof ResponseStatusException) { return (error.getCause() != null) ? error.getCause() : error; } return error; } private void addStackTrace(Map errorAttributes, Throwable error) { StringWriter stackTrace = new StringWriter(); error.printStackTrace(new PrintWriter(stackTrace)); stackTrace.flush(); errorAttributes.put("trace", stackTrace.toString()); } private void handleException(Map errorAttributes, Throwable error, boolean includeStackTrace) { if (this.includeException) { errorAttributes.put("exception", error.getClass().getName()); } if (includeStackTrace) { addStackTrace(errorAttributes, error); } if (error instanceof BindingResult) { BindingResult result = (BindingResult) error; if (result.hasErrors()) { errorAttributes.put("errors", result.getAllErrors()); } } } @Override public Throwable getError(ServerRequest request) { return (Throwable) request.attribute(ERROR_ATTRIBUTE) .orElseThrow(() -> new IllegalStateException( "Missing exception attribute in ServerWebExchange")); } @Override public void storeErrorInformation(Throwable error, ServerWebExchange exchange) { exchange.getAttributes().putIfAbsent(ERROR_ATTRIBUTE, error); }} DefaultErrorAttributes实现了ErrorAttributes接口，它的getErrorAttributes方法会返回timestamp、path、status、error、message、exception(
includeException)、trace(includeStackTrace)等信息；getError方法会从ServerRequest的ERROR_ATTRIBUTE中获取Throwable；storeErrorInformation则是把Throwable存放到ServerWebExchange的attributes中
WebExceptionHandler
spring-web-5.1.7.RELEASE-sources.jar!/org/springframework/web/server/WebExceptionHandler.java
public interface WebExceptionHandler { /** * Handle the given exception. A completion signal through the return value * indicates error handling is complete while an error signal indicates the * exception is still not handled. * @param exchange the current exchange * @param ex the exception to handle * @return {@code Mono} to indicate when exception handling is complete */ Mono handle(ServerWebExchange exchange, Throwable ex);} WebExceptionHandler定义了handle方法
ErrorWebExceptionHandler
spring-boot-2.1.5.RELEASE-sources.jar!/org/springframework/boot/web/reactive/error/ErrorWebExceptionHandler.java
@FunctionalInterfacepublic interface ErrorWebExceptionHandler extends WebExceptionHandler {}ErrorWebExceptionHandler继承了WebExceptionHandler接口，仅仅是通过类名来标识它用来render errors
AbstractErrorWebExceptionHandler
public abstract class AbstractErrorWebExceptionHandler implements ErrorWebExceptionHandler, InitializingBean { /** * Currently duplicated from Spring WebFlux HttpWebHandlerAdapter. */ private static final Set DISCONNECTED_CLIENT_EXCEPTIONS; static { Set exceptions = new HashSet<>(); exceptions.add("AbortedException"); exceptions.add("ClientAbortException"); exceptions.add("EOFException"); exceptions.add("EofException"); DISCONNECTED_CLIENT_EXCEPTIONS = Collections.unmodifiableSet(exceptions); } private static final Log logger = HttpLogging .forLogName(AbstractErrorWebExceptionHandler.class); private final ApplicationContext applicationContext; private final ErrorAttributes errorAttributes; private final ResourceProperties resourceProperties; private final TemplateAvailabilityProviders templateAvailabilityProviders; private List> messageReaders = Collections.emptyList(); private List> messageWriters = Collections.emptyList(); private List viewResolvers = Collections.emptyList(); public AbstractErrorWebExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties, ApplicationContext applicationContext) { Assert.notNull(errorAttributes, "ErrorAttributes must not be null"); Assert.notNull(resourceProperties, "ResourceProperties must not be null"); Assert.notNull(applicationContext, "ApplicationContext must not be null"); this.errorAttributes = errorAttributes; this.resourceProperties = resourceProperties; this.applicationContext = applicationContext; this.templateAvailabilityProviders = new TemplateAvailabilityProviders( applicationContext); } //...... @Override public void afterPropertiesSet() throws Exception { if (CollectionUtils.isEmpty(this.messageWriters)) { throw new IllegalArgumentException("Property 'messageWriters' is required"); } } /** * Create a {@link RouterFunction} that can route and handle errors as JSON responses * or HTML views. * * If the returned {@link RouterFunction} doesn't route to a {@code HandlerFunction}, * the original exception is propagated in the pipeline and can be processed by other * {@link org.springframework.web.server.WebExceptionHandler}s. * @param errorAttributes the {@code ErrorAttributes} instance to use to extract error * information * @return a {@link RouterFunction} that routes and handles errors */ protected abstract RouterFunction getRoutingFunction( ErrorAttributes errorAttributes); @Override public Mono handle(ServerWebExchange exchange, Throwable throwable) { if (exchange.getResponse().isCommitted() || isDisconnectedClientError(throwable)) { return Mono.error(throwable); } this.errorAttributes.storeErrorInformation(throwable, exchange); ServerRequest request = ServerRequest.create(exchange, this.messageReaders); return getRoutingFunction(this.errorAttributes).route(request) .switchIfEmpty(Mono.error(throwable)) .flatMap((handler) -> handler.handle(request)) .doOnNext((response) -> logError(request, response, throwable)) .flatMap((response) -> write(exchange, response)); } //......}
AbstractErrorWebExceptionHandler声明实现ErrorWebExceptionHandler以及InitializingBean接口；其handle方法首先把throwable存储到errorAttributes汇总，然后通过getRoutingFunction进行route；afterPropertiesSet主要是确保messageWriters不为空；它定义了getRoutingFunction要子类去实现
DefaultErrorWebExceptionHandler
spring-boot-autoconfigure-2.1.5.RELEASE-sources.jar!/org/springframework/boot/autoconfigure/web/reactive/error/DefaultErrorWebExceptionHandler.java
public class DefaultErrorWebExceptionHandler extends AbstractErrorWebExceptionHandler { private static final Map SERIES_VIEWS; static { Map views = new EnumMap<>(HttpStatus.Series.class); views.put(HttpStatus.Series.CLIENT_ERROR, "4xx"); views.put(HttpStatus.Series.SERVER_ERROR, "5xx"); SERIES_VIEWS = Collections.unmodifiableMap(views); } private final ErrorProperties errorProperties; /** * Create a new {@code DefaultErrorWebExceptionHandler} instance. * @param errorAttributes the error attributes * @param resourceProperties the resources configuration properties * @param errorProperties the error configuration properties * @param applicationContext the current application context */ public DefaultErrorWebExceptionHandler(ErrorAttributes errorAttributes, ResourceProperties resourceProperties, ErrorProperties errorProperties, ApplicationContext applicationContext) { super(errorAttributes, resourceProperties, applicationContext); this.errorProperties = errorProperties; } @Override protected RouterFunction getRoutingFunction( ErrorAttributes errorAttributes) { return route(acceptsTextHtml(), this::renderErrorView).andRoute(all(), this::renderErrorResponse); } /** * Render the error information as an HTML view. * @param request the current request * @return a {@code Publisher} of the HTTP response */ protected Mono renderErrorView(ServerRequest request) { boolean includeStackTrace = isIncludeStackTrace(request, MediaType.TEXT_HTML); Map error = getErrorAttributes(request, includeStackTrace); HttpStatus errorStatus = getHttpStatus(error); ServerResponse.BodyBuilder responseBody = ServerResponse.status(errorStatus) .contentType(MediaType.TEXT_HTML); return Flux .just("error/" + errorStatus.value(), "error/" + SERIES_VIEWS.get(errorStatus.series()), "error/error") .flatMap((viewName) -> renderErrorView(viewName, responseBody, error)) .switchIfEmpty(this.errorProperties.getWhitelabel().isEnabled() ? renderDefaultErrorView(responseBody, error) : Mono.error(getError(request))) .next(); } /** * Render the error information as a JSON payload. * @param request the current request * @return a {@code Publisher} of the HTTP response */ protected Mono renderErrorResponse(ServerRequest request) { boolean includeStackTrace = isIncludeStackTrace(request, MediaType.ALL); Map error = getErrorAttributes(request, includeStackTrace); return ServerResponse.status(getHttpStatus(error)) .contentType(MediaType.APPLICATION_JSON_UTF8) .body(BodyInserters.fromObject(error)); } /** * Determine if the stacktrace attribute should be included. * @param request the source request * @param produces the media type produced (or {@code MediaType.ALL}) * @return if the stacktrace attribute should be included */ protected boolean isIncludeStackTrace(ServerRequest request, MediaType produces) { ErrorProperties.IncludeStacktrace include = this.errorProperties .getIncludeStacktrace(); if (include == ErrorProperties.IncludeStacktrace.ALWAYS) { return true; } if (include == ErrorProperties.IncludeStacktrace.ON_TRACE_PARAM) { return isTraceEnabled(request); } return false; } /** * Get the HTTP error status information from the error map. * @param errorAttributes the current error information * @return the error HTTP status */ protected HttpStatus getHttpStatus(Map errorAttributes) { int statusCode = (int) errorAttributes.get("status"); return HttpStatus.valueOf(statusCode); } /** * Predicate that checks whether the current request explicitly support * {@code "text/html"} media type. * * The "match-all" media type is not considered here. * @return the request predicate */ protected RequestPredicate acceptsTextHtml() { return (serverRequest) -> { try { List acceptedMediaTypes = serverRequest.headers().accept(); acceptedMediaTypes.remove(MediaType.ALL); MediaType.sortBySpecificityAndQuality(acceptedMediaTypes); return acceptedMediaTypes.stream() .anyMatch(MediaType.TEXT_HTML::isCompatibleWith); } catch (InvalidMediaTypeException ex) { return false; } }; }}
DefaultErrorWebExceptionHandler继承了AbstractErrorWebExceptionHandler；其getRoutingFunction方法会对acceptsTextHtml的renderErrorView，其他的通过renderErrorResponse来返回json格式的错误信息
ExceptionHandlingWebHandler
spring-web-5.1.7.RELEASE-sources.jar!/org/springframework/web/server/handler/ExceptionHandlingWebHandler.java
public class ExceptionHandlingWebHandler extends WebHandlerDecorator { private final List exceptionHandlers; public ExceptionHandlingWebHandler(WebHandler delegate, List handlers) { super(delegate); this.exceptionHandlers = Collections.unmodifiableList(new ArrayList<>(handlers)); } /** * Return a read-only list of the configured exception handlers. */ public List getExceptionHandlers() { return this.exceptionHandlers; } @Override public Mono handle(ServerWebExchange exchange) { Mono completion; try { completion = super.handle(exchange); } catch (Throwable ex) { completion = Mono.error(ex); } for (WebExceptionHandler handler : this.exceptionHandlers) { completion = completion.onErrorResume(ex -> handler.handle(exchange, ex)); } return completion; }} ExceptionHandlingWebHandler继承了WebHandlerDecorator，它会挨个调用WebExceptionHandler的handle方法
小结
ErrorWebFluxAutoConfiguration注册了DefaultErrorAttributes、ErrorWebExceptionHandler
DefaultErrorAttributes实现了ErrorAttributes接口，它的getErrorAttributes方法会返回timestamp、path、status、error、message、exception(
includeException)、trace(includeStackTrace)等信息；getError方法会从ServerRequest的ERROR_ATTRIBUTE中获取Throwable；storeErrorInformation则是把Throwable存放到ServerWebExchange的attributes中DefaultErrorWebExceptionHandler继承了AbstractErrorWebExceptionHandler；其getRoutingFunction方法会对acceptsTextHtml的renderErrorView，其他的通过renderErrorResponse来返回json格式的错误信息
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