Java的。从FTP读取文件，但不要下载整个 [英] Java. Read file from FTP but DON'T download it whole

问题描述

我需要从FTP读取CSV文件头。

由于这些文件可能非常大，我不需要下载它们。 b
$ b

有没有办法从FTP读取第一行的CSV文件并中止连接？

解决方案

<只读只有第一行，忽略剩余和关闭流。一个聪明的FTP客户端在提供任何内容之前不会缓冲内存中的整个流。

假设您正在使用 Apache Commons Net FTPClient ：

 的BufferedReader读者=空; 
字符串firstLine = null; 
 
尝试{
 InputStream stream = ftpClient.retrieveFileStream（ftpFile.getName（））; 
 reader = new BufferedReader（new InputStreamReader（stream，UTF-8））; 
 firstLine = reader.readLine（）; 
} finally {
 if（reader！= null）try {reader.close（）; catch（IOException logOrIgnore）{} 
} 
 
 doYourThingWith（firstLine）; 
  

I need to read CSV file header from FTP.

As these files can be very huge, I don't need to download them.

Is there a way to read first line of CSV file from FTP and abort connection?

解决方案

Just read only the first line, ignore the remnant and close the stream. A smart FTP client won't buffer the entire stream in memory before providing anything for read.

Assuming you're using Apache Commons Net FTPClient:

BufferedReader reader = null;
String firstLine = null;

try {
    InputStream stream = ftpClient.retrieveFileStream(ftpFile.getName());
    reader = new BufferedReader(new InputStreamReader(stream, "UTF-8"));
    firstLine = reader.readLine();
} finally {
    if (reader != null) try { reader.close(); } catch (IOException logOrIgnore) {}
}

doYourThingWith(firstLine);

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