使用Java将文件从FTP下载到本地会导致文件无法读取 - 编码问题 [英] Downloading files from FTP to local using Java makes the file unreadable - encoding issues

问题描述

我开发了一个代码，可以从FTP读取非常大的文件，并使用Java将其写入本地计算机。它的代码如下。这是来自下一个（Text key，Text value）在的 RecordReader > CustomInputFormat

  if（！processed）
 {
 System.out .println（in processed）; 
 in = fs.open（file）; 
 processed = true; 
 
 while（bytesRead< = fileSize）{
 
 byte buf [] = new byte [1024]; 
 
尝试{
 in.read（buf）; 
 in.skip（1024）; 
 bytesRead + = 1024; 
 long diff = fileSize-bytesRead; 
 if（diff <1024）
 {
 break; 
} 
 value.set（buf，0，1024）; //这是记录的值被设置的位置，并且它将映射到映射器。 
} 
 catch（Exception e）
 {
 e.printStackTrace（）; 
} 
 
 
 if（diff <1024）
 {
 int difference =（int）（fileSize-bytesRead）; 
 
字节buf [] =新字节[区别]; 
 in.read（buf）; 
 bytesRead + =差异; 
} 
 
 System.out.println（closing stream）; 
 in.close（）; 
  

写入结束后，我看到传输已完成，文件大小目的地与源处相同。但是我无法打开文件，编辑器给出错误信息。

  gedit一直未能检测到字符编码。 
请检查您是否尝试打开二进制文件。 
从菜单中选择一个字符编码并重试。 
  

这个问题：与我相关的我相关，但是我无法读取文件，没有意义。

任何指针？

解决方案

您的复制代码是完整的，完全是100％A级废话。在Java中复制流的规范方法如下：

  int count; 
 byte [] buffer = new byte [8192]; （（count = in.read（buffer））> 0）
 {
 out.write（buffer，0，count）; //如果你喜欢
， 
} 
  

摆脱所有其他的毛病。这只是浪费时间和空间，并明显损害您的数据传输。

I have a developed a code that reads very large files from FTP and writes it to local machine using Java. The code that does it is as follows . This is a part from the next(Text key, Text value) inside the RecordReader of the CustomInputFormat

 if(!processed)
            {
                            System.out.println("in processed");
                in = fs.open(file);
    processed=true; 
            }
while(bytesRead <= fileSize) {

                 byte buf[] = new byte[1024]; 

                try {
                    in.read(buf);
                    in.skip(1024);
                    bytesRead+=1024;
                    long diff = fileSize-bytesRead;
                    if(diff<1024)
                    {
                        break;
                    }
        value.set(buf, 0, 1024); // This is where the value of the record is set and it goes to the mapper . 
                } 
                catch(Exception e)
                {
                    e.printStackTrace();
                }

            }
            if(diff<1024)
            {
                int difference= (int) (fileSize-bytesRead);

                 byte buf[] = new byte[difference]; 
                in.read(buf);
                bytesRead+=difference;
            }

                    System.out.println("closing stream");
                    in.close();

After the write is over , I see that the transfer is done and the size of the file at the destination is same as that at the source. But I am unable to open the file and the editor gives the error as

gedit has not been able to detect the character coding.
Please check that you are not trying to open a binary file.
Select a character coding from the menu and try again.

This Question: Java upload jpg using JakartaFtpWrapper - makes the file unreadable is related to mine I believe , but I couldn't make sense of it.

Any pointers ?

解决方案

Your copying code is complete and utter 100% A grade nonsense. The canonical way to copy a stream in Java is as follows:

int count;
byte[] buffer = new byte[8192]; // or more if you like
while ((count = in.read(buffer)) > 0)
{
  out.write(buffer, 0, count);
}

Get rid of all the other fluff. It is just wasting time and space and clearly damaging your data in transit.

这篇关于使用Java将文件从FTP下载到本地会导致文件无法读取 - 编码问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！