java下载文件时如何获取原始文件名

问题描述

当我像这样使用java从URL下载文件时如何获取原始文件名

How to get original file name when i download file from URL with java like this

File file = new File( "test" ) ;
FileUtils.copyURLToFile(URL, file)

因为当我创建文件时，我必须输入一个名称，但在这个阶段我还不知道下载文件的原始名称.

Because when i create file i must put a name but at this stage i don't know yet the original name of downloading file.

推荐答案

对我来说，建议的文件名存储在头文件 Content-Disposition 中:

For me the suggested file name is stored in the header file Content-Disposition:

Content-Disposition: attachment; filename="suggestion.zip"

我正在从 nexus 下载文件，因此对于不同的服务器/应用程序，它可能存储在不同的标头字段中，但使用诸如 firebug for firefox 之类的工具很容易找到.

I am downloading a file from nexus, so for different servers/applications it might be stored in a different header field but it is easy to find out with some tools like firebug for firefox.

以下几行对我来说很好

URL url = new URL(urlString);
// open the connection
URLConnection con = url.openConnection();
// get and verify the header field
String fieldValue = con.getHeaderField("Content-Disposition");
if (fieldValue == null || ! fieldValue.contains("filename=\"")) {
  // no file name there -> throw exception ...
}
// parse the file name from the header field
String filename = fieldValue.substring(fieldValue.indexOf("filename=\"") + 10, fieldValue.length() - 1);
// create file in systems temporary directory
File download = new File(System.getProperty("java.io.tmpdir"), filename);

// open the stream and download
ReadableByteChannel rbc = Channels.newChannel(con.getInputStream());
FileOutputStream fos = new FileOutputStream(download);
try {
  fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
} finally {
  fos.close();
}

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