spring.jackson.date-format: yyyy-MM-dd HH:mm:ss 无效bug追踪

springboot 2.x

spring.jackson.date-format 配置无效，Date 类型数据无法按照要求格式化。

@Override
	public void run() {
		bytes = mmInStream.read(buffer);
		mHandler.obtainMessage(READ_DATA, bytes, -1, buffer).sendToTarget();
	}

提示：这里填写问题的分析：

例如：Handler 发送消息有两种方式，分别是 Handler.obtainMessage()和 Handler.sendMessage()，其中 obtainMessage 方式当数据量过大时，由于 MessageQuene 大小也有限，所以当 message 处理不及时时，会造成先传的数据被覆盖，进而导致数据丢失。

RequestMappingHandlerAdapter ，这个类为controller 调用入口
// 这一行进行反射调用，并将结果放到对象中，需要在这块看下数据返回结果**
invocableMethod.invokeAndHandle(webRequest, mavContainer);

	@Nullable
	protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
			HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

		ServletWebRequest webRequest = new ServletWebRequest(request, response);
		try {
			WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
			ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);

			ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
			if (this.argumentResolvers != null) {
				invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
			}
			if (this.returnValueHandlers != null) {
				invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
			}
			invocableMethod.setDataBinderFactory(binderFactory);
			invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);

			ModelAndViewContainer mavContainer = new ModelAndViewContainer();
			mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
			modelFactory.initModel(webRequest, mavContainer, invocableMethod);
			mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

			AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
			asyncWebRequest.setTimeout(this.asyncRequestTimeout);

			WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
			asyncManager.setTaskExecutor(this.taskExecutor);
			asyncManager.setAsyncWebRequest(asyncWebRequest);
			asyncManager.registerCallableInterceptors(this.callableInterceptors);
			asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);

			if (asyncManager.hasConcurrentResult()) {
				Object result = asyncManager.getConcurrentResult();
				mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
				asyncManager.clearConcurrentResult();
				LogFormatUtils.traceDebug(logger, traceOn -> {
					String formatted = LogFormatUtils.formatValue(result, !traceOn);
					return "Resume with async result [" + formatted + "]";
				});
				invocableMethod = invocableMethod.wrapConcurrentResult(result);
			}
			**

// 这一行进行反射调用，并将结果放到对象中，需要在这块看下数据返回结果**
			invocableMethod.invokeAndHandle(webRequest, mavContainer);
			if (asyncManager.isConcurrentHandlingStarted()) {
				return null;
			}

			return getModelAndView(mavContainer, modelFactory, webRequest);
		}
		finally {
			webRequest.requestCompleted();
		}
	}

AbstractJackson2HttpMessageConverter 最后追踪到 objectWriter.writevalue(generator, value);
这行进行obj 转 json ，如果jackson 配置不生效，那问题还是处在 objectMapper 对象构建有问题

@Override
	protected void writeInternal(Object object, @Nullable Type type, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException {

		MediaType contentType = outputMessage.getHeaders().getContentType();
		JsonEncoding encoding = getJsonEncoding(contentType);
		JsonGenerator generator = this.objectMapper.getFactory().createGenerator(outputMessage.getBody(), encoding);
		try {
			writePrefix(generator, object);

			Object value = object;
			Class serializationView = null;
			FilterProvider filters = null;
			JavaType javaType = null;

			if (object instanceof MappingJacksonValue) {
				MappingJacksonValue container = (MappingJacksonValue) object;
				value = container.getValue();
				serializationView = container.getSerializationView();
				filters = container.getFilters();
			}
			if (type != null && TypeUtils.isAssignable(type, value.getClass())) {
				javaType = getJavaType(type, null);
			}

			ObjectWriter objectWriter = (serializationView != null ?
					this.objectMapper.writerWithView(serializationView) : this.objectMapper.writer());
			if (filters != null) {
				objectWriter = objectWriter.with(filters);
			}
			if (javaType != null && javaType.isContainerType()) {
				objectWriter = objectWriter.forType(javaType);
			}
			SerializationConfig config = objectWriter.getConfig();
			if (contentType != null && contentType.isCompatibleWith(MediaType.TEXT_EVENT_STREAM) &&
					config.isEnabled(SerializationFeature.INDENT_OUTPUT)) {
				objectWriter = objectWriter.with(this.ssePrettyPrinter);
			}
			objectWriter.writevalue(generator, value);

			writeSuffix(generator, object);
			generator.flush();
		}
		catch (InvalidDefinitionException ex) {
			throw new HttpMessageConversionException("Type definition error: " + ex.getType(), ex);
		}
		catch (JsonProcessingException ex) {
			throw new HttpMessageNotWritableException("Could not write JSON: " + ex.getOriginalMessage(), ex);
		}
	}

正常能格式化的时候如下图：

发现有问题项目的 objectMapper 对象如下图所示

一个项目中有两个 objectMapper 对象，一个设置的日期格式，一个没有设置。springboot 内部的 objectMapper 对象用的是没有设置日志格式的对象。

到底被谁覆盖了，没找到。

最后发现是 @EnableWebMvc 如果有这个注解，则 spring.jackson.date-format 配置无效。具体原因，需要进一步的源码追踪

Finally, if you opt out of the Spring Boot default MVC configuration by providing your own @EnableWebMvc configuration, you can take control completely and do everything manually by using getMessageConverters from WebMvcConfigurationSupport.

《Spring Boot Reference Guide》