快速解决commons-fileupload组件无法处理自定义head信息的bug

Jakarta commons fileupload组件可以处理HTTP请求及响应，很多时候被用来处理文件上传，但是近期发现，当我们自定义文件上传、自己组装mime信息、文件上传时加入自定义head节点时，fileupload组件无法获得自定义的head节点，仔细分析了fileupload组件源代码后，发现核心方法在FileUploadBase文件的findNextItem方法中，问题在于fileupload组件解析完自定义的head节点后，却忘记传递到FileItemStreamImpl中了，稍作修订，即可修正该bug。


代码如下:

/**解析文件列表
         * Called for finding the nex item, if any.
         * @return True, if an next item was found, otherwise false.
         * @throws IOException An I/O error occurred.
         */
        private boolean findNextItem() throws IOException {
            if (eof) {
                return false;
            }
            if (currentItem != null) {
                currentItem.close();
                currentItem = null;
            }
            for (;;) {
                boolean nextPart;
                if (skipPreamble) {
                    nextPart = multi.skipPreamble();
                } else {
                    nextPart = multi.readBoundary();
                }
                if (!nextPart) {
                    if (currentFieldName == null) {
                        // Outer multipart terminated -> No more data
                        eof = true;
                        return false;
                    }
                    // Inner multipart terminated -> Return to parsing the outer
                    multi.setBoundary(boundary);
                    currentFieldName = null;
                    continue;
                }
                FileItemHeaders headers = getParsedHeaders(multi.readHeaders());
                if (currentFieldName == null) {
                    // We're parsing the outer multipart
                    String fieldName = getFieldName(headers);
                    if (fieldName != null) {
                        String subContentType = headers.getHeader(CONTENT_TYPE);
                        if (subContentType != null
                                &&  subContentType.toLowerCase()
                                        .startsWith(MULTIPART_MIXED)) {
                            currentFieldName = fieldName;
                            // Multiple files associated with this field name
                            byte[] subBoundary = getBoundary(subContentType);
                            multi.setBoundary(subBoundary);
                            skipPreamble = true;
                            continue;
                        }
                        String fileName = getFileName(headers);
                        currentItem = new FileItemStreamImpl(fileName,
                                fieldName, headers.getHeader(CONTENT_TYPE),
                                fileName == null, getContentLength(headers));
                        notifier.noteItem();
                        itemValid = true;
                        return true;
                    }
                } else {
                    String fileName = getFileName(headers);
                    if (fileName != null) {
                             //这里代码要修订
                        //这是原来的代码，没有传入header
                        //currentItem = new FileItemStreamImpl(fileName, currentFieldName,headers.getHeader(CONTENT_TYPE),false, getContentLength(headers));
                        //这是新的代码，我们要传入header
                        currentItem = new FileItemStreamImpl(fileName, currentFieldName,headers.getHeader(CONTENT_TYPE),false, getContentLength(headers),headers);
                        notifier.noteItem();
                        itemValid = true;
                        return true;
                    }
                }
                multi.discardBodyData();
            }
        }

/**原始代码，存在丢失FileItemHeaders信息的bug
             * Creates a new instance.
             * @param pName The items file name, or null.
             * @param pFieldName The items field name.
             * @param pContentType The items content type, or null.
             * @param pFormField Whether the item is a form field.
             * @param pContentLength The items content length, if known, or -1
             * @throws IOException Creating the file item failed.
             */
            FileItemStreamImpl(String pName, String pFieldName,
                    String pContentType, boolean pFormField,
                    long pContentLength) throws IOException {
                name = pName;
                fieldName = pFieldName;
                contentType = pContentType;
                formField = pFormField;
                final ItemInputStream itemStream = multi.newInputStream();
                InputStream istream = itemStream;
                if (fileSizeMax != -1) {
                    if (pContentLength != -1
                            &&  pContentLength > fileSizeMax) {
                        FileUploadException e =
                            new FileSizeLimitExceededException(
                                "The field " + fieldName
                                + " exceeds its maximum permitted "
                                + " size of " + fileSizeMax
                                + " characters.",
                                pContentLength, fileSizeMax);
                        throw new FileUploadIOException(e);
                    }
                    istream = new LimitedInputStream(istream, fileSizeMax) {
                        protected void raiseError(long pSizeMax, long pCount)
                                throws IOException {
                            itemStream.close(true);
                            FileUploadException e =
                                new FileSizeLimitExceededException(
                                    "The field " + fieldName
                                    + " exceeds its maximum permitted "
                                    + " size of " + pSizeMax
                                    + " characters.",
                                    pCount, pSizeMax);
                            throw new FileUploadIOException(e);
                        }
                    };
                }
                stream = istream;
            }

/**创建FileItem，修订后的代码，解决丢失FileItemHeaders信息的bug
             * @param pName
             * @param pFieldName
             * @param pContentType
             * @param pFormField
             * @param pContentLength
             * @param headers
             * @throws IOException
             */
            FileItemStreamImpl(String pName, String pFieldName,
                    String pContentType, boolean pFormField,
                    long pContentLength,FileItemHeaders headers) throws IOException {
                name = pName;
                fieldName = pFieldName;
                contentType = pContentType;
                formField = pFormField;
                if(headers!=null){
                        this.headers = headers;
                }
                final ItemInputStream itemStream = multi.newInputStream();
                InputStream istream = itemStream;
                if (fileSizeMax != -1) {
                    if (pContentLength != -1
                            &&  pContentLength > fileSizeMax) {
                        FileUploadException e =
                            new FileSizeLimitExceededException(
                                "The field " + fieldName
                                + " exceeds its maximum permitted "
                                + " size of " + fileSizeMax
                                + " characters.",
                                pContentLength, fileSizeMax);
                        throw new FileUploadIOException(e);
                    }
                    istream = new LimitedInputStream(istream, fileSizeMax) {
                        protected void raiseError(long pSizeMax, long pCount)
                                throws IOException {
                            itemStream.close(true);
                            FileUploadException e =
                                new FileSizeLimitExceededException(
                                    "The field " + fieldName
                                    + " exceeds its maximum permitted "
                                    + " size of " + pSizeMax
                                    + " characters.",
                                    pCount, pSizeMax);
                            throw new FileUploadIOException(e);
                        }
                    };
                }
                stream = istream;
            }