org.springframework.http.converter.HttpMessageNotWritableException: No converter for [class xxx] with preset Content-Type ''application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8''

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先说解决方法

解决方法有两种：

第一种：把接口返回值改为void。

第二种：用response.reset()置空返回值里的ContentType，让处理器自己选择合适的ContentType来转换返回值，不过这样的话返回给前端的ContentType也为空，前端就没法根据ContentType来判断文件的格式，需要前端自行设置文件格式。

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问题代码

问题现象为导出功能可以正常使用，但日志里会报错“无法转换返回值”，这报错虽然不影响使用，但看着总是很不顺眼的嘛。

public MessageResp<String> exportExcel(@RequestBody Req req, HttpServletResponse response) throws Exception {
try (ServletoutputStream out = response.getoutputStream()) {
     String fileName = URLEncoder.encode("导出表格.xlsx", "UTF-8");
     response.reset();
     response.setContentType("application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8");
     response.setHeader("Content-disposition", "attachment;filename=" + fileName + ";" + "filename*=utf-8''''" + fileName);
     DgExcelUtil.getXlsx("导出sheet", exportClass, titleList, exportList).write(out);
} catch (Exception e) {
     LOGGER.error("导出报错：", e);
     throw new SmkException(ErrorCode.FAIL, "导出报错");
}
return new MessageResp<>();

---

报错日志

org.springframework.http.converter.HttpMessageNotWritableException: No converter for [class com.sk.financial.dg.supervision.response.MessageResp] with preset Content-Type ''application/vnd.openxmlformats-officedocument.spreadsheetml.sheet;charset=utf-8''
	at org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:312)
	at org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:181)
	at org.springframework.web.method.support.HandlerMethodReturnValueHandlerComposite.handleReturnValue(HandlerMethodReturnValueHandlerComposite.java:78)
	at org.springframework.web.servlet.mvc.method.annotation.ServletinvocableHandlerMethod.invokeAndHandle(ServletinvocableHandlerMethod.java:124)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:894)
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808)
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
	at org.springframework.web.servlet.dispatcherServlet.dodispatch(dispatcherServlet.java:1063)
	at org.springframework.web.servlet.dispatcherServlet.doService(dispatcherServlet.java:963)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:681)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:228)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at com.sk.financial.dg.supervision.config.filter.SimpleCORSFilter.doFilter(SimpleCORSFilter.java:24)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at com.sk.financial.dg.supervision.config.filter.LogbackFilter.doFilter(LogbackFilter.java:43)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at com.alibaba.druid.support.http.WebStatFilter.doFilter(WebStatFilter.java:124)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at com.sk.financial.dg.supervision.config.filter.ReplaceStreamFilter.doFilter(ReplaceStreamFilter.java:36)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:190)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:163)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:357)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:382)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:893)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1723)
	at org.apache.tomcat.util.net.socketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)

---

原因排查

点进报错日志的第一个文件AbstractMessageConverterMethodProcesso的writeWithMessageConverters方法，可以看到这样一段代码，它检测返回值中是否设置了contentType，有则把它赋给selectedMediaType，没有就从所有MediaType里自动选择匹配到的MediaType，赋给selectedMediaType。

MediaType selectedMediaType = null;
MediaType contentType = outputMessage.getHeaders().getContentType();
boolean isContentTypePreset = contentType != null && contentType.isConcrete();
if (isContentTypePreset) {
    if (logger.isDebugEnabled()) {
        logger.debug("Found ''Content-Type:" + contentType + "'' in response");
    }
    selectedMediaType = contentType;
}
else {
    HttpServletRequest request = inputMessage.getServletRequest();
    List<MediaType> acceptableTypes;
    try {
        acceptableTypes = getAcceptableMediaTypes(request);
    }
    catch (HttpMediaTypeNotAcceptableException ex) {
        int series = outputMessage.getServletResponse().getStatus() / 100;
        if (body == null || series == 4 || series == 5) {
            if (logger.isDebugEnabled()) {
                logger.debug("Ignoring error response content (if any). " + ex);
            }
            return;
        }
        throw ex;
    }
    List<MediaType> producibleTypes = getProducibleMediaTypes(request, valueType, targettype);

    if (body != null && producibleTypes.isEmpty()) {
        throw new HttpMessageNotWritableException(
                "No converter found for return value of type: " + valueType);
    }
    List<MediaType> mediaTypestoUse = new ArrayList<>();
    for (MediaType requestedType : acceptableTypes) {
        for (MediaType producibleType : producibleTypes) {
            if (requestedType.isCompatibleWith(producibleType)) {
                mediaTypestoUse.add(getMostSpecificmediaType(requestedType, producibleType));
            }
        }
    }
    if (mediaTypestoUse.isEmpty()) {
        if (body != null) {
            throw new HttpMediaTypeNotAcceptableException(producibleTypes);
        }
        if (logger.isDebugEnabled()) {
            logger.debug("No match for " + acceptableTypes + ", supported: " + producibleTypes);
        }
        return;
    }

    MediaType.sortBySpecificityAndQuality(mediaTypestoUse);

    for (MediaType mediaType : mediaTypestoUse) {
        if (mediaType.isConcrete()) {
            selectedMediaType = mediaType;
            break;
        }
        else if (mediaType.isPresentIn(ALL_APPLICATION_MEDIA_TYPES)) {
            selectedMediaType = MediaType.APPLICATION_OCTET_STREAM;
            break;
        }
    }

    if (logger.isDebugEnabled()) {
        logger.debug("Using ''" + selectedMediaType + "'', given " +
                acceptableTypes + " and supported " + producibleTypes);
    }
}

而在下一段代码中，selectedMediaType被用于转换返回值，报错是因为找到的selectedMediaType与返回值不匹配，没有通过((GenericHttpMessageConverter) converter).canWrite(targettype, valueType, selectedMediaType)判断，从而抛出异常。

if (selectedMediaType != null) {
    selectedMediaType = selectedMediaType.removeQualityValue();
    for (HttpMessageConverter<?> converter : this.messageConverters) {
        GenericHttpMessageConverter genericConverter = (converter instanceof GenericHttpMessageConverter ?
                (GenericHttpMessageConverter<?>) converter : null);
        if (genericConverter != null ?
                ((GenericHttpMessageConverter) converter).canWrite(targettype, valueType, selectedMediaType) :
                converter.canWrite(valueType, selectedMediaType)) {
            body = getAdvice().beforeBodyWrite(body, returnType, selectedMediaType,
                    (Class<? extends HttpMessageConverter<?>>) converter.getClass(),
                    inputMessage, outputMessage);
            if (body != null) {
                Object theBody = body;
                LogFormatUtils.traceDebug(logger, traceOn ->
                        "Writing [" + LogFormatUtils.formatValue(theBody, !traceOn) + "]");
                addContentdispositionHeader(inputMessage, outputMessage);
                if (genericConverter != null) {
                    genericConverter.write(body, targettype, selectedMediaType, outputMessage);
                }
                else {
                    ((HttpMessageConverter) converter).write(body, selectedMediaType, outputMessage);
                }
            }
            else {
                if (logger.isDebugEnabled()) {
					logger.debug("nothing to write: null body");
				}
			}
			return;
		}
	}
}

if (body != null) {
    Set<MediaType> producibleMediaTypes =
            (Set<MediaType>) inputMessage.getServletRequest()
                    .getAttribute(HandlerMapping.PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE);

    if (isContentTypePreset || !CollectionUtils.isEmpty(producibleMediaTypes)) {
        throw new HttpMessageNotWritableException(
                "No converter for [" + valueType + "] with preset Content-Type ''" + contentType + "''");
    }
    throw new HttpMediaTypeNotAcceptableException(getSupportedMediaTypes(body.getClass()));
}

因此可以通过置空返回值里的ContentType，来让处理器自行选择。

org.springframework.http.converter.HttpMessageNotWritableException: No converter found for return value of type: class com.lcy.pojo.User

【原因】找不到返回值类型的转换器，找了好久发现controller返回的是json格式数据

【方案】在maven的pox.xml中只引入Json的依赖时，只引入了“jackson-core”；没有引入 “jackson-databind”，添加了依赖后问题解决了。

【提示】当controller标记@ResponseBody后，会用解析器去解析Controller的返回值，解析器会去寻找SpringMvc中注册的HttpMeesageConverter接口的实现类，结果因为没有添加对应的依赖，所以

就找不到Json类型的转换器了，添加依赖后就正常了。



【正确的依赖】

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
        <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>2.9.8</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.8</version>
        </dependency>

 public class MyRequest {    @JsonProperty("my_name")    private String myName;    @JsonProperty("my_phone")    private String myPhone;    //Getters and Setters of myName and myPhone.    }

@RequestMapping(        value = "/rest/sth",        method = RequestMethod.POST)public ResponseEntity<String> create(@RequestBody MultiValueMap paramMap) { ... }

    HashMap<String, Object> newMap = new HashMap<>();    Arrays.asList(new String[]{"my_name", "my_phone"})            .forEach( k -> newMap.put(k, ((List<?>) paramMap.get(k)).get(0)));    MyRequest myrequest = new ObjectMapper().convertValue(newMap, MyRequest.class);

Cannot resolve configuration property ''xxxx''

@Value("${}")