解决Required request part 'file' is not present

hola2025-06-05 11:10

背景

起因：调用上传图片接口出现错误Required request part 'file' is not present​

CURL:

shell 复制代码 
curl --location 'localhost:8080/file/upload' \
--form 'file=@"/C:/Users/Leaf/Pictures/头像/a.jpg"'

检查了接口传参Content-Type​类型正常，为multipart/form-data​

报错异常：

shell 复制代码 
org.springframework.web.multipart.support.MissingServletRequestPartException: Required request part 'file' is not present
	at org.springframework.web.method.annotation.RequestParamMethodArgumentResolver.handleMissingValueInternal(RequestParamMethodArgumentResolver.java:213) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.method.annotation.RequestParamMethodArgumentResolver.handleMissingValue(RequestParamMethodArgumentResolver.java:193) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.method.annotation.AbstractNamedValueMethodArgumentResolver.resolveArgument(AbstractNamedValueMethodArgumentResolver.java:114) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.method.support.HandlerMethodArgumentResolverComposite.resolveArgument(HandlerMethodArgumentResolverComposite.java:122) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.method.support.InvocableHandlerMethod.getMethodArgumentValues(InvocableHandlerMethod.java:179) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:146) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:117) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:895) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:808) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1072) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:965) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:909) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:555) ~[tomcat-embed-core-9.0.82.jar:4.0.FR]
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.3.30.jar:5.3.30]
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:623) ~[tomcat-embed-core-9.0.82.jar:4.0.FR]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:209) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51) ~[tomcat-embed-websocket-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at com.leaf.filter.RequestFilter.doFilter(RequestFilter.java:30) ~[classes/:na]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.30.jar:5.3.30]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.30.jar:5.3.30]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.3.30.jar:5.3.30]
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:117) ~[spring-web-5.3.30.jar:5.3.30]
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:178) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:153) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:168) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:90) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:481) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:130) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:93) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:390) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:63) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:928) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1794) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:52) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.82.jar:9.0.82]
	at java.base/java.lang.Thread.run(Thread.java:834) ~[na:na]

‍

分析原因

  1. 代码中请求过滤器处理请求之前，调用过getParameterMap()方法，该方法是通过读取请求的输入流来获取数据的。关键点在于：Servlet 的输入流只能被读取一次；
  2. 代码中配置了CommonsMultipartResolver解析器来解析文件请求，这个解析器也是通过读取请求的输入流来获取数据，因此读取流的时候失败，因为输入流已经被消费了；
  3. 而如果不配置 MultipartResolver ，Spring Boot 会使用默认的 StandardServletMultipartResolver，它是基于 Servlet 3.0+ 的 Part API 实现的，而不是直接读取输入流。它的核心是 request.getParts() 方法；
  4. Servlet 容器在第一次调用 getParts() 时会解析整个请求体，将解析结果缓存在请求对象中，后续调用 getParts() 时直接返回缓存的结果，而不是重新解析。

‍

CommonsMultipartResolver​和StandardServletMultipartResolver​主要区别：

  1. 解析时机：

    • StandardServletMultipartResolver：依赖 Servlet 容器的 getParts() 方法，只解析一次
    • CommonsMultipartResolver：直接读取输入流，每次都需要重新解析

  2. 数据存储：

    • StandardServletMultipartResolver：数据由 Servlet 容器缓存
    • CommonsMultipartResolver：需要自己管理数据

  3. 性能影响：

    • StandardServletMultipartResolver：第一次解析后，后续调用都是使用缓存
    • CommonsMultipartResolver：每次都需要重新解析

‍

建议

  1. 如果使用 Servlet 3.0+ 环境，优先使用 StandardServletMultipartResolver
  2. 如果需要更细粒度的控制或自定义解析逻辑，才考虑使用 CommonsMultipartResolver
  3. 如果使用 CommonsMultipartResolver，要避免在解析前调用 request.getParameterMap()

‍

源码

getParameterMap()​部分源码：

java 复制代码 
@Override
    public Map<String,String[]> getParameterMap() {

        if (parameterMap.isLocked()) {
            return parameterMap;
        }

        Enumeration<String> enumeration = getParameterNames();
        while (enumeration.hasMoreElements()) {
            String name = enumeration.nextElement();
            String[] values = getParameterValues(name);
            parameterMap.put(name, values);
        }

        parameterMap.setLocked(true);

        return parameterMap;

    }

@Override
    public Enumeration<String> getParameterNames() {

        if (!parametersParsed) {
            parseParameters();
        }

        return coyoteRequest.getParameters().getParameterNames();

    }

protected void parseParameters() {

        parametersParsed = true;

        Parameters parameters = coyoteRequest.getParameters();
        boolean success = false;
        try {
            // Set this every time in case limit has been changed via JMX
            int maxParameterCount = getConnector().getMaxParameterCount();
            if (parts != null && maxParameterCount > 0) {
                maxParameterCount -= parts.size();
            }
            parameters.setLimit(maxParameterCount);

            // getCharacterEncoding() may have been overridden to search for
            // hidden form field containing request encoding
            Charset charset = getCharset();

            boolean useBodyEncodingForURI = connector.getUseBodyEncodingForURI();
            parameters.setCharset(charset);
            if (useBodyEncodingForURI) {
                parameters.setQueryStringCharset(charset);
            }
            // Note: If !useBodyEncodingForURI, the query string encoding is
            // that set towards the start of CoyoteAdapter.service()

            parameters.handleQueryParameters();

            if (usingInputStream || usingReader) {
                success = true;
                return;
            }

            String contentType = getContentType();
            if (contentType == null) {
                contentType = "";
            }
            int semicolon = contentType.indexOf(';');
            if (semicolon >= 0) {
                contentType = contentType.substring(0, semicolon).trim();
            } else {
                contentType = contentType.trim();
            }

            if ("multipart/form-data".equals(contentType)) {
                parseParts(false);
                success = true;
                return;
            }

            // ...
            success = true;
        } finally {
            if (!success) {
                parameters.setParseFailedReason(FailReason.UNKNOWN);
            }
        }

    }


// parts.add(part); 后续用默认的StandardServletMultipartResolver解析，会调用getPart()能够从缓存拿到数据
private void parseParts(boolean explicit) {

        // Return immediately if the parts have already been parsed
        if (parts != null || partsParseException != null) {
            return;
        }

        Context context = getContext();
        MultipartConfigElement mce = getWrapper().getMultipartConfigElement();

        if (mce == null) {
            if (context.getAllowCasualMultipartParsing()) {
                mce = new MultipartConfigElement(null, connector.getMaxPostSize(), connector.getMaxPostSize(),
                        connector.getMaxPostSize());
            } else {
                if (explicit) {
                    partsParseException = new IllegalStateException(sm.getString("coyoteRequest.noMultipartConfig"));
                    return;
                } else {
                    parts = Collections.emptyList();
                    return;
                }
            }
        }

        int maxParameterCount = getConnector().getMaxParameterCount();
        Parameters parameters = coyoteRequest.getParameters();
        parameters.setLimit(maxParameterCount);

        boolean success = false;
        try {
            File location;
            String locationStr = mce.getLocation();
            if (locationStr == null || locationStr.length() == 0) {
                location = ((File) context.getServletContext().getAttribute(ServletContext.TEMPDIR));
            } else {
                // If relative, it is relative to TEMPDIR
                location = new File(locationStr);
                if (!location.isAbsolute()) {
                    location = new File((File) context.getServletContext().getAttribute(ServletContext.TEMPDIR),
                            locationStr).getAbsoluteFile();
                }
            }

            if (!location.exists() && context.getCreateUploadTargets()) {
                log.warn(sm.getString("coyoteRequest.uploadCreate", location.getAbsolutePath(),
                        getMappingData().wrapper.getName()));
                if (!location.mkdirs()) {
                    log.warn(sm.getString("coyoteRequest.uploadCreateFail", location.getAbsolutePath()));
                }
            }

            if (!location.isDirectory()) {
                parameters.setParseFailedReason(FailReason.MULTIPART_CONFIG_INVALID);
                partsParseException = new IOException(sm.getString("coyoteRequest.uploadLocationInvalid", location));
                return;
            }


            // Create a new file upload handler
            DiskFileItemFactory factory = new DiskFileItemFactory();
            try {
                factory.setRepository(location.getCanonicalFile());
            } catch (IOException ioe) {
                parameters.setParseFailedReason(FailReason.IO_ERROR);
                partsParseException = ioe;
                return;
            }
            factory.setSizeThreshold(mce.getFileSizeThreshold());

            ServletFileUpload upload = new ServletFileUpload();
            upload.setFileItemFactory(factory);
            upload.setFileSizeMax(mce.getMaxFileSize());
            upload.setSizeMax(mce.getMaxRequestSize());
            if (maxParameterCount > -1) {
                // There is a limit. The limit for parts needs to be reduced by
                // the number of parameters we have already parsed.
                // Must be under the limit else parsing parameters would have
                // triggered an exception.
                upload.setFileCountMax(maxParameterCount - parameters.size());
            }

            parts = new ArrayList<>();
            try {
                List<FileItem> items = upload.parseRequest(new ServletRequestContext(this));
                int maxPostSize = getConnector().getMaxPostSize();
                int postSize = 0;
                Charset charset = getCharset();
                for (FileItem item : items) {
                    ApplicationPart part = new ApplicationPart(item, location);
                    parts.add(part);
                    if (part.getSubmittedFileName() == null) {
                        String name = part.getName();
                        if (maxPostSize >= 0) {
                            // Have to calculate equivalent size. Not completely
                            // accurate but close enough.
                            postSize += name.getBytes(charset).length;
                            // Equals sign
                            postSize++;
                            // Value length
                            postSize += part.getSize();
                            // Value separator
                            postSize++;
                            if (postSize > maxPostSize) {
                                parameters.setParseFailedReason(FailReason.POST_TOO_LARGE);
                                throw new IllegalStateException(sm.getString("coyoteRequest.maxPostSizeExceeded"));
                            }
                        }
                        String value = null;
                        try {
                            value = part.getString(charset.name());
                        } catch (UnsupportedEncodingException uee) {
                            // Not possible
                        }
                        parameters.addParameter(name, value);
                    }
                }

                success = true;
            } catch (InvalidContentTypeException e) {
                parameters.setParseFailedReason(FailReason.INVALID_CONTENT_TYPE);
                partsParseException = new ServletException(e);
            } catch (SizeException e) {
                parameters.setParseFailedReason(FailReason.POST_TOO_LARGE);
                checkSwallowInput();
                partsParseException = new IllegalStateException(e);
            } catch (IOException e) {
                parameters.setParseFailedReason(FailReason.IO_ERROR);
                partsParseException = e;
            } catch (IllegalStateException e) {
                // addParameters() will set parseFailedReason
                checkSwallowInput();
                partsParseException = e;
            }
        } finally {
            // This might look odd but is correct. setParseFailedReason() only
            // sets the failure reason if none is currently set. This code could
            // be more efficient but it is written this way to be robust with
            // respect to changes in the remainder of the method.
            if (partsParseException != null || !success) {
                parameters.setParseFailedReason(FailReason.UNKNOWN);
            }
        }
    }

‍

CommonsMultipartResolver​部分源码：

java 复制代码 
@Override
	public MultipartHttpServletRequest resolveMultipart(final HttpServletRequest request) throws MultipartException {
		Assert.notNull(request, "Request must not be null");
		if (this.resolveLazily) {
			return new DefaultMultipartHttpServletRequest(request) {
				@Override
				protected void initializeMultipart() {
					MultipartParsingResult parsingResult = parseRequest(request);
					setMultipartFiles(parsingResult.getMultipartFiles());
					setMultipartParameters(parsingResult.getMultipartParameters());
					setMultipartParameterContentTypes(parsingResult.getMultipartParameterContentTypes());
				}
			};
		}
		else {
			MultipartParsingResult parsingResult = parseRequest(request);
			return new DefaultMultipartHttpServletRequest(request, parsingResult.getMultipartFiles(),
					parsingResult.getMultipartParameters(), parsingResult.getMultipartParameterContentTypes());
		}
	}

protected MultipartParsingResult parseRequest(HttpServletRequest request) throws MultipartException {
		String encoding = determineEncoding(request);
		FileUpload fileUpload = prepareFileUpload(encoding);
		try {
			List<FileItem> fileItems = ((ServletFileUpload) fileUpload).parseRequest(request);
			return parseFileItems(fileItems, encoding);
		}
		catch (FileUploadBase.SizeLimitExceededException ex) {
			throw new MaxUploadSizeExceededException(fileUpload.getSizeMax(), ex);
		}
		catch (FileUploadBase.FileSizeLimitExceededException ex) {
			throw new MaxUploadSizeExceededException(fileUpload.getFileSizeMax(), ex);
		}
		catch (FileUploadException ex) {
			throw new MultipartException("Failed to parse multipart servlet request", ex);
		}
	}

@Override
    public List<FileItem> parseRequest(HttpServletRequest request)
    throws FileUploadException {
        return parseRequest(new ServletRequestContext(request));
    }

public List<FileItem> parseRequest(RequestContext ctx)
            throws FileUploadException {
        List<FileItem> items = new ArrayList<FileItem>();
        boolean successful = false;
        try {
            FileItemIterator iter = getItemIterator(ctx);
            FileItemFactory fac = getFileItemFactory();
            final byte[] buffer = new byte[Streams.DEFAULT_BUFFER_SIZE];
            if (fac == null) {
                throw new NullPointerException("No FileItemFactory has been set.");
            }
            while (iter.hasNext()) {
                if (items.size() == fileCountMax) {
                    // The next item will exceed the limit.
                    throw new FileCountLimitExceededException(ATTACHMENT, getFileCountMax());
                }
                final FileItemStream item = iter.next();
                // Don't use getName() here to prevent an InvalidFileNameException.
                final String fileName = ((FileItemIteratorImpl.FileItemStreamImpl) item).name;
                FileItem fileItem = fac.createItem(item.getFieldName(), item.getContentType(),
                                                   item.isFormField(), fileName);
                items.add(fileItem);
                try {
                    Streams.copy(item.openStream(), fileItem.getOutputStream(), true, buffer);
                } catch (FileUploadIOException e) {
                    throw (FileUploadException) e.getCause();
                } catch (IOException e) {
                    throw new IOFileUploadException(format("Processing of %s request failed. %s",
                                                           MULTIPART_FORM_DATA, e.getMessage()), e);
                }
                final FileItemHeaders fih = item.getHeaders();
                fileItem.setHeaders(fih);
            }
            successful = true;
            return items;
        } catch (FileUploadIOException e) {
            throw (FileUploadException) e.getCause();
        } catch (IOException e) {
            throw new FileUploadException(e.getMessage(), e);
        } finally {
            if (!successful) {
                for (FileItem fileItem : items) {
                    try {
                        fileItem.delete();
                    } catch (Exception ignored) {
                        // ignored TODO perhaps add to tracker delete failure list somehow?
                    }
                }
            }
        }
    }

public FileItemIterator getItemIterator(RequestContext ctx)
    throws FileUploadException, IOException {
        try {
            return new FileItemIteratorImpl(ctx);
        } catch (FileUploadIOException e) {
            // unwrap encapsulated SizeException
            throw (FileUploadException) e.getCause();
        }
    }

// ctx.getInputStream() 调用的是ServletRequestContext的getInputStream()方法来读取流
FileItemIteratorImpl(RequestContext ctx)
                throws FileUploadException, IOException {
            if (ctx == null) {
                throw new NullPointerException("ctx parameter");
            }

            String contentType = ctx.getContentType();
            if ((null == contentType)
                    || (!contentType.toLowerCase(Locale.ENGLISH).startsWith(MULTIPART))) {
                throw new InvalidContentTypeException(
                        format("the request doesn't contain a %s or %s stream, content type header is %s",
                               MULTIPART_FORM_DATA, MULTIPART_MIXED, contentType));
            }


            @SuppressWarnings("deprecation") // still has to be backward compatible
            final int contentLengthInt = ctx.getContentLength();

            final long requestSize = UploadContext.class.isAssignableFrom(ctx.getClass())
                                     // Inline conditional is OK here CHECKSTYLE:OFF
                                     ? ((UploadContext) ctx).contentLength()
                                     : contentLengthInt;
                                     // CHECKSTYLE:ON

            InputStream input; // N.B. this is eventually closed in MultipartStream processing
            if (sizeMax >= 0) {
                if (requestSize != -1 && requestSize > sizeMax) {
                    throw new SizeLimitExceededException(
                        format("the request was rejected because its size (%s) exceeds the configured maximum (%s)",
                                Long.valueOf(requestSize), Long.valueOf(sizeMax)),
                               requestSize, sizeMax);
                }
                // N.B. this is eventually closed in MultipartStream processing
                input = new LimitedInputStream(ctx.getInputStream(), sizeMax) {
                    @Override
                    protected void raiseError(long pSizeMax, long pCount)
                            throws IOException {
                        FileUploadException ex = new SizeLimitExceededException(
                        format("the request was rejected because its size (%s) exceeds the configured maximum (%s)",
                                Long.valueOf(pCount), Long.valueOf(pSizeMax)),
                               pCount, pSizeMax);
                        throw new FileUploadIOException(ex);
                    }
                };
            } else {
                input = ctx.getInputStream();
            }

            String charEncoding = headerEncoding;
            if (charEncoding == null) {
                charEncoding = ctx.getCharacterEncoding();
            }

            boundary = getBoundary(contentType);
            if (boundary == null) {
                IOUtils.closeQuietly(input); // avoid possible resource leak
                throw new FileUploadException("the request was rejected because no multipart boundary was found");
            }

            notifier = new MultipartStream.ProgressNotifier(listener, requestSize);
            try {
                multi = new MultipartStream(input, boundary, notifier);
            } catch (IllegalArgumentException iae) {
                IOUtils.closeQuietly(input); // avoid possible resource leak
                throw new InvalidContentTypeException(
                        format("The boundary specified in the %s header is too long", CONTENT_TYPE), iae);
            }
            multi.setHeaderEncoding(charEncoding);

            skipPreamble = true;
            findNextItem();
        }

@Override
    public InputStream getInputStream() throws IOException {
        return request.getInputStream();
    }

‍

StandardServletMultipartResolver​部分源码：

java 复制代码 
@Override
	public MultipartHttpServletRequest resolveMultipart(HttpServletRequest request) throws MultipartException {
		return new StandardMultipartHttpServletRequest(request, this.resolveLazily);
	}

public StandardMultipartHttpServletRequest(HttpServletRequest request, boolean lazyParsing)
			throws MultipartException {

		super(request);
		if (!lazyParsing) {
			parseRequest(request);
		}
	}

// request.getParts() 调用的是getParameterMap()中的parts数组，这时候可以拿到缓存数据
private void parseRequest(HttpServletRequest request) {
		try {
			Collection<Part> parts = request.getParts();
			this.multipartParameterNames = new LinkedHashSet<>(parts.size());
			MultiValueMap<String, MultipartFile> files = new LinkedMultiValueMap<>(parts.size());
			for (Part part : parts) {
				String headerValue = part.getHeader(HttpHeaders.CONTENT_DISPOSITION);
				ContentDisposition disposition = ContentDisposition.parse(headerValue);
				String filename = disposition.getFilename();
				if (filename != null) {
					if (filename.startsWith("=?") && filename.endsWith("?=")) {
						filename = MimeDelegate.decode(filename);
					}
					files.add(part.getName(), new StandardMultipartFile(part, filename));
				}
				else {
					this.multipartParameterNames.add(part.getName());
				}
			}
			setMultipartFiles(files);
		}
		catch (Throwable ex) {
			handleParseFailure(ex);
		}
	}

‍

解决方案

  1. 使用默认的StandardServletMultipartResolver​；

  2. 使用CommonsMultipartResolver​，需要额外引入依赖commons-fileupload​，且手动提前解析multipart请求：

    java 复制代码 
    // 手动解析 multipart 请求
HttpServletRequest processedRequest = httpRequest;
if (isMultipartRequest(httpRequest)) {
    try {
        processedRequest = multipartResolver.resolveMultipart(httpRequest);
    } catch (Exception e) {
        log.warn("Failed to parse multipart request", e);
    }
}

// 罪魁祸首，getParameterMap()中解析了multipart请求，消费了请求流，当请求到达Controller时，再次尝试解析而找不到文件报错
Map<String, String[]> parameterMap = httpRequest.getParameterMap();

chain.doFilter(processedRequest, response);

‍

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