我从FTP服务器下载的文件长度与服务器上的文件长度不相同

Question

我正在使用Java中的FTPClient从服务器下载文件。当文件被下载时，我想检查它的完整性，然后删除它。 我这样做是通过比较下载的文件（以字节为单位）和服务器上的文件（以字节为单位）的大小来实现的，但结果与预期不符。

下面是从我的传输目录的摘录：

for (int i = 0; i <= insideDirectory.length - 1; i++) { 
        FTPFile transferFile = insideDirectory[i]; 
        LOGGER.info("Passing file" + folder.getName() + "/" + transferFile.getName()); 

        File downloadFile = new File("https://stackoverflow.com/users/home/example" + i + ".mp4"); 
        OutputStream outputStream2 = new BufferedOutputStream(new FileOutputStream(downloadFile)); 
        System.out.println(transferFile.getSize()); 
        ftpClient.enterLocalPassiveMode(); 
        ftpClient.setFileType(FTP.BINARY_FILE_TYPE); 
        InputStream inputStream = ftpClient 
          .retrieveFileStream(folder.getName() + "/" + transferFile.getName()); 
        byte[] bytesArray = new byte[4096]; 
        int bytesRead = -1; 
        while ((bytesRead = inputStream.read(bytesArray)) != -1) { 
         outputStream2.write(bytesArray, 0, bytesRead); 
        } 

        Boolean success = ftpClient.completePendingCommand(); 
        if (success) { 
         System.out.println("File #" + i + " has been downloaded successfully."); 
         checkIfExists(downloadFile, transferFile); 
        } 

下面是我checkIfExists方法

public void checkIfExists(File downloadedFile, FTPFile remoteFileToDelete) { 
    Long downloadedLength = downloadedFile.length(); 
    Long remoteLength = remoteFileToDelete.getSize(); 
    if (downloadedFile.length() == remoteFileToDelete.getSize()) { 
     LOGGER.info(downloadedLength + "exists and is the same length as " + remoteLength + ". Let's delete"); 
    } else { 
     LOGGER.info(downloadedLength + "is not the same length as " + remoteLength + ". Let's not delete"); 
    } 
} 

这里是输出运行循环两次之后，你可以看到，大小下载的文件可能有所不同：

 File #0 has been downloaded successfully. 
    INFO: 7596008is not the same length as 7600840. Let's not delete 
    File #1 has been downloaded successfully. 
    INFO: 6873664is not the same length as 6878544. Let's not delete 
    File #2 has been downloaded successfully. 
    INFO: 7558112is not the same length as 7564744. Let's not delete 
    File #3 has been downloaded successfully. 
    INFO: 8662336is not the same length as 8665108. Let's not delete 

    File #0 has been downloaded successfully. 
    INFO: 7594312is not the same length as 7600840. Let's not delete 
    File #1 has been downloaded successfully. 
    INFO: 6870392is not the same length as 6878544. Let's not delete 
    File #2 has been downloaded successfully. 
    INFO: 7559184is not the same length as 7564744. Let's not delete 
    File #3 has been downloaded successfully. 
    INFO: 8660888is not the same length as 8665108. Let's not delete 

Answer 1

.close()您的BufferedOutputStream，然后再尝试测量写入文件的大小。

如果没有.close()，则无法保证（实际上恰恰相反）您写入流中的所有数据实际上都将写入通过File对象访问的基础文件。