有没有一种很好、安全、快速的方法来将 InputStream 写入 Scala 中的文件？
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/2782638/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Is there a nice, safe, quick way to write an InputStream to a File in Scala?
提问by pr1001
Specifically, I'm saving a file upload to local file in a Lift web app.
具体来说，我将文件上传保存到 Lift Web 应用程序中的本地文件。
采纳答案by Rex Kerr
If it's a text file, and you want to limit yourself to Scala and Java, then using scala.io.Sourceto do the reading is probably the fastest--it's not built in, but easy to write:
如果它是一个文本文件，并且您想将自己限制在 Scala 和 Java，那么scala.io.Source用于读取可能是最快的——它不是内置的，但易于编写：
def inputToFile(is: java.io.InputStream, f: java.io.File) {
val in = scala.io.Source.fromInputStream(is)
val out = new java.io.PrintWriter(f)
try { in.getLines().foreach(out.println(_)) }
finally { out.close }
}
But if you need other libraries anyway, you can make your life even easier by using them (as Michel illustrates).
但是，如果您无论如何都需要其他库，则可以通过使用它们使您的生活更加轻松（如 Michel 所示）。
(P.S.--in Scala 2.7, getLinesshould not have a ()after it.)
（PS--在 Scala 2.7 中，后面getLines不应该有()。）
(P.P.S.--in old versions of Scala, getLinesdid not remove the newline, so you need to printinstead of println.)
（PPS——在旧版本的 Scala 中，getLines没有删除换行符，所以你需要print代替println.）
回答by notan3xit
With Java 7 or later you can use Filesfrom the new File I/O:
使用 Java 7 或更高版本，您可以Files从新的 File I/O 使用：
Files.copy(from, to)
where fromand tocan be Paths or InputStreams. This way, you can even use it to conveniently extract resources from applications packed in a jar.
其中from和to可以是Paths 或InputStreams。这样，您甚至可以使用它从打包在 jar 中的应用程序中方便地提取资源。
回答by Michel Kr?mer
I don't know about any Scala specific API, but since Scala is fully compatible to Java you can use any other library like Apache Commons IOand Apache Commons FileUpload.
我不知道任何特定于 Scala 的 API，但由于 Scala 与 Java 完全兼容，因此您可以使用任何其他库，如Apache Commons IO和Apache Commons FileUpload。
Here is some example code (untested):
这是一些示例代码（未经测试）：
//using Commons IO:
val is = ... //input stream you want to write to a file
val os = new FileOutputStream("out.txt")
org.apache.commons.io.IOUtils.copy(is, os)
os.close()
//using Commons FileUpload
import javax.servlet.http.HttpServletRequest
import org.apache.commons.fileupload.{FileItemFactory, FileItem}
import apache.commons.fileupload.disk.DiskFileItemFactory
import org.apache.commons.fileupload.servlet.ServletFileUpload
val request: HttpServletRequest = ... //your HTTP request
val factory: FileItemFactory = new DiskFileItemFactory()
val upload = new ServletFileUpload(factory)
val items = upload.parseRequest(request).asInstanceOf[java.util.List[FileItem]]
for (item <- items) item.write(new File(item.getName))
回答by phidias
The inputToFile method given above doesn't work well with binary files like .pdf files. It throws a runtime exception while attempting to decode the file into string. What worked for me was this:
上面给出的 inputToFile 方法不适用于 .pdf 文件等二进制文件。它在尝试将文件解码为字符串时抛出运行时异常。对我有用的是：
def inputStreamToFile(inputStream: java.io.InputStream, file: java.io.File) = {
val fos = new java.io.FileOutputStream(file)
fos.write(
Stream.continually(inputStream.read).takeWhile(-1 !=).map(_.toByte).toArray
)
fos.close()
}
