Sping Boot 提供了默认值，可以排除或使用用户提供的bean。这是关键功能之一。
假设WebFlux ErrorExceptionHandler当前看起来是这样的，

@AutoConfiguration(before = WebFluxAutoConfiguration.class)
@ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.REACTIVE)
@ConditionalOnClass(WebFluxConfigurer.class)
@EnableConfigurationProperties({ ServerProperties.class, WebProperties.class })
public class ErrorWebFluxAutoConfiguration {

    private final ServerProperties serverProperties;

    public ErrorWebFluxAutoConfiguration(ServerProperties serverProperties) {
        this.serverProperties = serverProperties;
    }

    @Bean
    @ConditionalOnMissingBean(value = ErrorWebExceptionHandler.class, search = SearchStrategy.CURRENT)
    @Order(-1)
    public ErrorWebExceptionHandler errorWebExceptionHandler(ErrorAttributes errorAttributes,
            WebProperties webProperties, ObjectProvider<ViewResolver> viewResolvers,
            ServerCodecConfigurer serverCodecConfigurer, ApplicationContext applicationContext) {
        DefaultErrorWebExceptionHandler exceptionHandler = new DefaultErrorWebExceptionHandler(errorAttributes,
                webProperties.getResources(), this.serverProperties.getError(), applicationContext);
        exceptionHandler.setViewResolvers(viewResolvers.orderedStream().toList());
        exceptionHandler.setMessageWriters(serverCodecConfigurer.getWriters());
        exceptionHandler.setMessageReaders(serverCodecConfigurer.getReaders());
        return exceptionHandler;
    }

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

}

你也可以
1.创建实现ErrorWebExceptionHandler而不是WebExceptionHandler的Bean
1.不包括ErrorWebFluxAutoConfiguration.class，它可以通过几种方式完成，但现在通常通过@SpringBootApplication(exclude = { ErrorWebFluxAutoConfiguration.class })完成。