I am probably overlooking something but what's the right way to create a file Path from a folder Path? This is what I'm doing but it seems wrong to convert the folder path to a string just to reconstruct it. Is there a better way?
Path testFolder = Files.createTempDirectory("fileFinder");
Path testFile = Paths.get(testFolder.toString(), "sample.java");
Files.createFile(testFile);
Path testFile = Files.createFile(Files.createTempDirectory("fileFinder").resolve("sample.java"));
But maybe all you need is just one tempfile:
Path testFile = Files.createTempFile("fileFinder");
Path class has resolve() method to join two paths together. It is overloaded to take a String as a parameter (other path).
So your expression to produce the combined path will be:
testfolder.resolve("sample.java")
Related
If I created a two paths such as:
Path path3 = Paths.get("E:\\data");
Path path4 = Paths.get("E:\\user\\home");
And then make a new Path(relativePath) by using the relativize() method on the two paths, creating: "..\user\home" does the path symbol(..) in this case refer to "data" or does it just indicate a relative path?
Path relativePath = path3.relativize(path4);
// ..\user\home <- output
So my Question is, what does the Path symbol (..) represent?
The relativize method needs two inputs but doesn't "secretly" encode the base path into it's output, so your relativePath has to be applied to another base path to actually access a path on disk.
But you can apply it to a different base path, e.g. if you want to sync two folder structures below two different base paths.
tl;dr: it just indicates a relative path.
But take care with your path separator: if you hardcode that into your path strings like in your example, it will fail on other systems. Better split up the individual parts in extra strings like this:
Path path4 = Paths.get("E:", "user", "home");
I'm copy files from a jar to a local folder.
The jar is located at a/b.
The folder (in the jar) I'm trying to extract is located at b/c
The destination folder should be z, i.e. a/b/c/x -> z/x
When I use c.relativize("x") I get ../c/x instead of x.
This is a problem when I then try to do: z.resolve(c.relativize(x)).
I get z/../c/x instead of z/x
How do I fix this issue?
I tried z.resolve(c.relativize(x).normalise()) but get the same result
The jar is b in the folder a. c is a resource (folder) inside the jar b. x is a file inside the folder c.
The jar is in folder A/B/
The source folder path inside the jar is /b/c/ with file /b/c/xxx.yyy
The destination folder is Z
The destination file should have path: Z/xxx.yyy
So:
Path sourceZip = Paths.get("/A/B/my.zip");
URI sourceZipURI = URI.create("jar:" + sourceZip.toUri());
Path targetFolder = Paths.get("/Z");
Map<String, Object> senv = new HashMap<>();
try (FileSystem sourceZipFS = FileSystems.newFileSystem(sourceZipURI, senv, null)) {
Path folderInZip = sourceZipFS.getPath("/b/c");
Files.list(folderInZip).forEach(p -> {
Path target = targetFolder.resolve(folderInZip.relativize(p).toString());
try {
Files.createDirectories(target.getParent());
Files.copy(p, target);
} catch (IOException e) {
e.printStackTrace();
}
});
}
The main issue was the reversal of relativize; not the first time I encountered the misunderstanding. child.relativize(parent) gives a .. whereas parent.relativize(child) truncates the path.
To get the target path one needs to convert the source Path to a string, to prevent combining two different file systems.
(I did not take care of subdirectories.)
I think you have misunderstood the usage of path.relativize(Path)
According to https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/nio/file/Path.html#relativize(java.nio.file.Path), there is a statement as below:
Constructs a relative path between this path and a given path.
e.g.
Path pathA = Paths.get("a"); // i.e. /a or /anyDir/anySubDir/a
Path pathB = Paths.get("b"); // i.e. /b or /anyDir/anySubDir/b
pathA.relativize(pathB)
Assume the result is ../b, what does it mean?
It is actually telling you: as you are inside directory a, if you want to access directory b, you need to access by this approach cd ../b.
relativize(Path) is helping to analyzing the relative path between the parent Path and the child Path (i.e. how to access from parent Path to child Path).
Alternatively, from your question, looks like you are preferring to "construct" the path instead of "analyzing" the relative path. relativize(Path) is not the one for this purpose.
So, which one, "construct" manually or "analyze", do you want to achieve?
I'm playing around with the NIO Path stuff, and came across this quesion:
What will the following code fragment print?
Path p1 = Paths.get("\\personal\\readme.txt");
Path p2 = Paths.get("\\index.html");
Path p3 = p1.relativize(p2);
System.out.println(p3);
The answer is
..\..\index.html
But this would make the entire Path:
\personal\readme.txt\index.html
This looks like nonsense to me, as you can't put a file within a file like this. Can you?
If readme.txt were a directory instead of a file, I would be perfectly OK with this, but I'm very confused as to why it allows a filepath like this to exist?
Or is there some weird way that you can actually do this?
Both ISOs and Zip files (therefore JAR/WAR/XUL/CHM...) represent files that can contain a folder structure of files. These files can be handled either as a file, or as a folder; both are legitimate uses for them. Therefore, this would be semantically meaningful:
Path p1 = Paths.get("\\personal\\photos.zip");
Path p2 = Paths.get("\\family\\me.png");
Path p3 = p1.relativize(p2);
System.out.println(p3);"
While I am not aware of any implementations in Java that behave this way, it is a semantic used in XUL and Windows Explorer.
The result is ..\..\index.html
From the javadoc:
This method attempts to construct a relative path that when resolved
against this path, yields a path that locates the same file as the
given path. For example, on UNIX, if this path is "/a/b" and the given
path is "/a/b/c/d" then the resulting relative path would be "c/d".
Where this path and the given path do not have a root component, then
a relative path can be constructed.
This means that you would have to go up two folders from this path to reach a path from which you can reach your given path, index.html.
Remember, these are all paths, not actual files/file descriptors.
Path p1 = Paths.get("\\personal\\readme.txt");
Path p2 = Paths.get("\\personal\\index.html");
Path p3 = p1.relativize(p2);
System.out.println(p3);
prints ..\index.html, meaning from \\personal\\readme.txt, go up one and then access index.html.
I am using the new Path object of java 7 and I am running into an issue.
I have a file storage system with a base directory and I create my own relative path. In the end I want to store just this relative path somewhere. I am running into a problem with Path.relativize though.
I have two usecases.
1.
Path baseDir = Paths.get("uploads");
Path filename = Paths.get("uploads/image/test.png")
return baseDir.relativize(filename);
This returns a Path image/test.png, which is perfect.
However, usecase 2:
Path baseDir = Paths.get("uploads");
Path filename = Paths.get("image/test.png")
return baseDir.relativize(filename);
returns ../image/test.png. I just want it to return "image/test.png"
In the Path tutorial it says
In the absence of any other information, it is assumed that 2 Paths are siblings
What I want is to be able to detect that this is the case. In this case, I want to just return the filename and ignore the baseDir.
I currently solve it like this, but I was hoping there was a better way:
Path rootEnding = getRootDirectory().getName(getRootDirectory().getNameCount() - 1);
for (Path part : path) {
if (part.equals(rootEnding)) {
return getRootDirectory().relativize(path);
}
}
return path;
So my question is, is there any better way of checking this?
Try adding a normalize() after relativize(). It seems to intended to do exactly this (remove unnecessary .. and . ). Don't miss the caution about symlinks in the javadoc.
This isn't 100% equivalent to what you wrote above, but I think it does what you want. Basically, let baseDir be a relative path. Pretend that whatever baseDir is relative to is the root of the file system. Then allow filename to be either relative or absolute from this "simulated root".
What about:
if (filename.startsWith(baseDir)) {
filename = baseDir.relativize(filename);
}
I have a directory pointed to by a File object called baseDir in which I keep most of my files.
I have a String f which may contain a relative filename, like "data.gz", or an absolute filename like "/mnt/data.gz" (its specified in a config file).
In the event that f is relative, it should be assumed that the file specified is within baseDir, but if it is absolute then it should be treated accordingly.
How do I create a File object that points to the file represented by f?
I can think of hacky solutions to this (eg. if (f.startsWith("/")) ... but I'm hoping there is a "right way" to do this.
Oh, I tried using the File(File, String) constructor for the File object, but it doesn't do what I need it to do.
Use File.isAbsolute(x)
http://download.oracle.com/javase/6/docs/api/java/io/File.html#isAbsolute%28%29
If this returns false, prepend your basedir.
You can try the following:
File file = new File(f);
if(file.isAbsolute())
...
Be careful that the definition of absolute path is system dependent!