【排错日记】The supplied file was empty (zero bytes long)

背景

使用了hutool的excel工具类ExcelUtil

现象

org.apache.poi.EmptyFileException: The supplied file was empty (zero bytes long)
	at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:222)
	at org.apache.poi.poifs.filesystem.POIFSFileSystem.<init>(POIFSFileSystem.java:172)
	at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:280)
	at org.apache.poi.ss.usermodel.WorkbookFactory.create(WorkbookFactory.java:253)
	at cn.hutool.poi.excel.WorkbookUtil.createBook(WorkbookUtil.java:84)
	at cn.hutool.poi.excel.WorkbookUtil.createSXSSFBook(WorkbookUtil.java:166)
	at cn.hutool.poi.excel.WorkbookUtil.createSXSSFBook(WorkbookUtil.java:154)
	at cn.hutool.poi.excel.BigExcelWriter.<init>(BigExcelWriter.java:96)
	at cn.hutool.poi.excel.BigExcelWriter.<init>(BigExcelWriter.java:86)
	at cn.hutool.poi.excel.ExcelUtil.getBigWriter(ExcelUtil.java:395)

日志分析

1. 日志表明：加载excel时，原文件为空报错。

代码分析

1. 关键业务代码

    File tempFile = FileUtil.createTempFile("check-batch-bill", ".xlsx", SystemUtils.getJavaIoTmpDir(), true);
    ExcelWriter writer = ExcelUtil.getBigWriter(tempFile);
    writer.write(lists, true);
   

   代码逻辑：

   • 创建一个空临时文件。
   • excelwriter 关联该空临时文件。
   • 将内容写入该空临时文件。

2. 源码

   ExcelUtil.getBigWriter源码位置

   /**
   	 * 获得{@link BigExcelWriter}，默认写出到第一个sheet，名字为sheet1
   	 *
   	 * @param destFile 目标文件
   	 * @return {@link BigExcelWriter}
   	 */
   public static BigExcelWriter getBigWriter(File destFile) {
   	try {
   		return new BigExcelWriter(destFile);
   	} catch (NoClassDefFoundError e) {
   		throw new DependencyException(ObjectUtil.defaultIfNull(e.getCause(), e), PoiChecker.NO_POI_ERROR_MSG);
   	}
   }
   
   
   
   /**
    * 构造
    *
    * @param destFile 目标文件，可以不存在
    * @param sheetName sheet名，做为第一个sheet名并写出到此sheet，例如sheet1
    */
   public BigExcelWriter(File destFile, String sheetName) {
   	this(destFile.exists() ? WorkbookUtil.createSXSSFBook(destFile) : WorkbookUtil.createSXSSFBook(), sheetName);
   	this.destFile = destFile;
   }
   
   
   
       private POIFSFileSystem(FileChannel channel, File srcFile, boolean readOnly, boolean closeChannelOnError) throws IOException {
           this(false);
   
           try {
               if (srcFile != null) {
                   if (srcFile.length() == 0L) {
                       throw new EmptyFileException();
                   }
   
                   FileBackedDataSource d = new FileBackedDataSource(srcFile, readOnly);
                   channel = d.getChannel();
                   this._data = d;
               } else {
                   this._data = new FileBackedDataSource(channel, readOnly);
               }
   
               ByteBuffer headerBuffer = ByteBuffer.allocate(512);
               IOUtils.readFully(channel, headerBuffer);
               this._header = new HeaderBlock(headerBuffer);
               this.readCoreContents();
           } catch (RuntimeException | IOException var6) {
               if (closeChannelOnError && channel != null) {
                   channel.close();
               }
   
               throw var6;
           }
       }
   

   报错 部分是：

    if (srcFile.length() == 0L) {
          throw new EmptyFileException();
    }
   

   结论：

   可以知道，创建空的临时文件是不可行的，而应该指定一个目录。

   如

    ExcelWriter writer = ExcelUtil.getBigWriter("dir");
    writer.write(lists, true);