Java 为文件生成 URL
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Generate URL for File
提问by Dónal
The default output of File.toURL()is
的默认输出File.toURL()是
file:/c:/foo/bar
These don't appear to work on windows, and need to be changed to
这些似乎在 Windows 上不起作用，需要更改为
file:///c:/foo/bar
Does the format
有没有格式
file:/foo/bar
work correctly on Unix (I don't have a Unix machine to test on)? Is there a library that can take care of generating a URL from a File that is in the correct format for the current environment?
在 Unix 上正常工作（我没有要测试的 Unix 机器）？是否有一个库可以处理从当前环境正确格式的文件中生成 URL 的库？
I've considered using a regex to fix the problem, something like:
我考虑过使用正则表达式来解决问题，例如：
fileUrl.replaceFirst("^file:/", "file:///")
However, this isn't quite right, because it will convert a correct URL like:
但是，这不太正确，因为它会转换正确的 URL，例如：
file:///c:/foo/bar
to:
到：
file://///c:/foo/bar
Update
更新
I'm using Java 1.4 and in this version File.toURL()is not deprecated and both File.toURL().toString()and File.toURI().toString()generate the same (incorrect) URL on windows
我使用的Java 1.4和在这个版本File.toURL()没有弃用，都File.toURL().toString()和File.toURI().toString()产生的窗口相同（不正确）网址
回答by aperkins
The File.toURL() method is deprecated - it is recommended that you use the toURI() method instead. If you use that instead, does your problem go away?
File.toURL() 方法已弃用 - 建议您改用 toURI() 方法。如果你改用它，你的问题会消失吗？
Edit:
编辑：
I understand: you are using Java 4. However, your question did not explain what you were trying to do. If, as you state in the comments, you are attempting to simply read a file, use a FileReaderto do so (or a FileInputStreamif the file is a binary format).
我理解：您使用的是 Java 4。但是，您的问题并没有解释您想要做什么。如果，如您在评论中所述，您只是尝试读取文件，请使用FileReader来执行此操作（如果文件是二进制格式，则使用FileInputStream）。
回答by Jonik
What do you actually mean with "Does the format file:/c:/foo/barwork correctly on Unix"?
“格式file:/c:/foo/bar在 Unix 上是否正常工作”实际上是什么意思？
Some examples from Unix.
一些来自 Unix 的例子。
File file = new File("/tmp/foo.txt"); // this file exists
System.out.println(file.toURI()); // "file:/tmp/foo.txt"
However, you cannot e.g. do this:
但是，您不能这样做：
File file = new File("file:/tmp/foo.txt");
System.out.println(file.exists()); // false
(If you need a URLinstance, do file.toURI().toURL()as the Javadoc says.)
（如果你需要一个URL实例，file.toURI().toURL()按照Javadoc 说的去做。）
Edit: how about the following, does it help?
编辑：以下内容如何，有帮助吗？
URL url = new URL("file:/tmp/foo.txt");
System.out.println(url.getFile()); // "/tmp/foo.txt"
File file = new File(url.getFile());
System.out.println(file.exists()); // true
(Basically very close to BalusC's example which used new File(url.toURI()).)
（基本上非常接近 BalusC 使用的示例new File(url.toURI())。）
回答by BalusC
The File(String)expects a pathname, not an URL. If you want to construct a Filebased on a Stringwhich actually represents an URL, then you'll need to convert this Stringback to URLfirst and make use of File(URI)to construct the Filebased on URL#toURI().
将File(String)需要一个路径，而不是URL。如果您想File根据String实际表示 URL 的a构造 a ，那么您需要将其转换String回URLfirst 并利用File(URI)来构造File基于 的URL#toURI()。
String urlAsString = "file:/c:/foo/bar";
URL url = new URL(urlAsString);
File file = new File(url.toURI());
Update:since you're on Java 1.4 and URL#toURI()is actually a Java 1.5 method (sorry, overlooked that bit), better use URL#getPath()instead which returns the pathname, so that you can use File(String).
更新：由于您使用的是 Java 1.4 并且URL#toURI()实际上是 Java 1.5 方法（抱歉，忽略了这一点），最好使用URL#getPath()返回路径名的方法，以便您可以使用File(String).
String urlAsString = "file:/c:/foo/bar";
URL url = new URL(urlAsString);
File file = new File(url.getPath());
