I have have a file that I want to use in my project which is in the resources package
src.res
Following what was stated in this answer, I believe that my code is valid.
File fil = new File("/res/t2.nii");
// Prints C:\\res\\t2.nii
System.out.println(fil.getAbsolutePath());
The problem is that I that file is in my projects file not there, so I get an Exception.
How am I suppose to properly convert from relative path to absolute?
Try with directory first that will provide you absolute path of directory then use file.exists() method to check for file existence.
File fil = new File("res"); // no forward slash in the beginning
System.out.println(fil.getAbsolutePath()); // Absolute path of res folder
Find more variants of File Path & Operations
Must read Oracle Java Tutorial on What Is a Path? (And Other File System Facts)
A path is either relative or absolute.
An absolute path always contains the root element and the complete directory list required to locate the file.
For example, /res/images is an absolute path.
A relative path needs to be combined with another path in order to access a file.
For example, res/images is a relative path. Without more information, a program cannot reliably locate the res/images directory in the file system.
Since you are using a Java package, you must to use a class loader if you want to load a resource. e.g.:
URL url = ClassLoader.getSystemResource("res/t2.nii");
if (url != null) {
File file = new File(url.toURI());
System.out.println(file.getAbsolutePath());
}
You can notice that ClassLoader.getSystemResource("res/t2.nii") returns URL object for reading the resource, or null if the resource could not be found. The next line convertes the given URL into an abstract pathname.
See more in Preferred way of loading resources in Java.
validate with
if (fil.exists()) { }
before and check if it really exist. if not then you can get the current path with
System.getProperty("user.dir"));
to validate that you are starting fromt he proper path.
if you really want to access the path you shouldnt use absolut pathes / since it will as explained start from the root of your Harddisk.
you can get the absolut path of the res folder by using this what my poster was writte in the previous answer:
File fil = new File("res");
System.out.println(fil.getAbsolutePath());
Related
This feels like it should be something straight forward, but I can seem to find an elegant solution to it without converting to File.
Given a Path
Path path = Paths.get("/a/b/foo")
How to do get the path /a/b/foo.bar? subpath will return a relative path regardless of whether the original path is relative or absolute.
I would prefer not to have to use additional libraries. But, maybe that is the only way?
To change the file name of a Path, use one of the resolveSibling() methods:
This is useful where a file name needs to be replaced with another file name.
Using this method ensures that the result Path object is for the same FileSystem as the source Path object.
So, to add extension ".bar" to a Path:
path = path.resolveSibling(path.getFileName() + ".bar");
I have a pdf file in my web project at the below location :
"static/Downloadables/20/Home_insurance_booklet.pdf "
"static" is present in the WebContent. The context root of the project is "pas".
In one of the jsp, I need to check if the file Home_insurance_booklet.pdf exists or not. I tried in many ways but unable to succeed. Below is the code I have used.
String filePath = request.getContextPath()+"/static/Downloadables/20/Home_insurance_booklet.pdf";
if(new File(filePath.toString()).exists()) {
------
}
Through the file exists, the condition is returning false. How to check if the file exists or not w.r.t to certain location in the root of the web project ?
Edit:
File path displayed is
/pas/static/Downloadables/20/Home_insurance_booklet.pdf
Try the following:
String path = getServletContext().getRealPath("/static/Downloadables/20/Home_insurance_booklet.pdf")
File file = new File(path)
if (file.exists()) {
// Success
}
And here is the API-Doc of getRealPath():
http://docs.oracle.com/javaee/6/api/javax/servlet/ServletContext.html#getRealPath(java.lang.String)
Use
ServletContext context = request.getServletContext();
StringBuilder finalPathToFile = new StringBuilder(context.getRealPath("/"));
The ServletContext#getRealPath() converts a web content path (the path in the expanded WAR folder structure on the server's disk file system) to an absolute disk file system path.
The "/" represents the web content root.
After that append in this way :
finalPathToFile.append("/static/Downloadables/20/Home_insurance_booklet.pdf");
Then use
if(new File(finalPathToFile.toString()).exists()) {
---------------------
doWhateverYouWantToDo
---------------------
}
check whether file is loaded in the project or not. and then try for absolute path first of the file in your code then try for relative path.
You have to use a file system based URL instead of relative web based URL.
I need to get a resource image file in a java project. What I'm doing is:
URL url = TestGameTable.class.getClass().
getClassLoader().getResource("unibo.lsb.res/dice.jpg");
The directory structure is the following:
unibo/
lsb/
res/
dice.jpg
test/
..../ /* other packages */
The fact is that I always get as the file doesn't exist. I have tried many different paths, but I couldn't solve the issue.
Any hint?
TestGameTable.class.getResource("/unibo/lsb/res/dice.jpg");
leading slash to denote the root of the classpath
slashes instead of dots in the path
you can call getResource() directly on the class.
Instead of explicitly writing the class name you could use
this.getClass().getResource("/unibo/lsb/res/dice.jpg");
if you are calling from static method, use :
TestGameTable.class.getClassLoader().getResource("dice.jpg");
One thing to keep in mind is that the relevant path here is the path relative to the file system location of your class... in your case TestGameTable.class. It is not related to the location of the TestGameTable.java file.
I left a more detailed answer here... where is resource actually located
I am developing a tool, which takes a path of an xml file. Now that path can be either relative or absolute. Inside the code, when I have only a string, is there a way to identify that the path is absolute or relative?
How about File.isAbsolute():
File file = new File(path);
if (file.isAbsolute()) {
...
}
There is another very similar way using Paths operations:
Path p = Paths.get(pathName);
if (p.isAbsolute()) {
...
}
What's the difference between getPath(), getAbsolutePath(), and getCanonicalPath() in Java?
And when do I use each one?
Consider these filenames:
C:\temp\file.txt - This is a path, an absolute path, and a canonical path.
.\file.txt - This is a path. It's neither an absolute path nor a canonical path.
C:\temp\myapp\bin\..\\..\file.txt - This is a path and an absolute path. It's not a canonical path.
A canonical path is always an absolute path.
Converting from a path to a canonical path makes it absolute (usually tack on the current working directory so e.g. ./file.txt becomes c:/temp/file.txt). The canonical path of a file just "purifies" the path, removing and resolving stuff like ..\ and resolving symlinks (on unixes).
Also note the following example with nio.Paths:
String canonical_path_string = "C:\\Windows\\System32\\";
String absolute_path_string = "C:\\Windows\\System32\\drivers\\..\\";
System.out.println(Paths.get(canonical_path_string).getParent());
System.out.println(Paths.get(absolute_path_string).getParent());
While both paths refer to the same location, the output will be quite different:
C:\Windows
C:\Windows\System32\drivers
The best way I have found to get a feel for things like this is to try them out:
import java.io.File;
public class PathTesting {
public static void main(String [] args) {
File f = new File("test/.././file.txt");
System.out.println(f.getPath());
System.out.println(f.getAbsolutePath());
try {
System.out.println(f.getCanonicalPath());
}
catch(Exception e) {}
}
}
Your output will be something like:
test\..\.\file.txt
C:\projects\sandbox\trunk\test\..\.\file.txt
C:\projects\sandbox\trunk\file.txt
So, getPath() gives you the path based on the File object, which may or may not be relative; getAbsolutePath() gives you an absolute path to the file; and getCanonicalPath() gives you the unique absolute path to the file. Notice that there are a huge number of absolute paths that point to the same file, but only one canonical path.
When to use each? Depends on what you're trying to accomplish, but if you were trying to see if two Files are pointing at the same file on disk, you could compare their canonical paths. Just one example.
In short:
getPath() gets the path string that the File object was constructed with, and it may be relative current directory.
getAbsolutePath() gets the path string after resolving it against the current directory if it's relative, resulting in a fully qualified path.
getCanonicalPath() gets the path string after resolving any relative path against current directory, and removes any relative pathing (. and ..), and any file system links to return a path which the file system considers the canonical means to reference the file system object to which it points.
Also, each of these has a File equivalent which returns the corresponding File object.
Note that IMO, Java got the implementation of an "absolute" path wrong; it really should remove any relative path elements in an absolute path. The canonical form would then remove any FS links or junctions in the path.
getPath() returns the path used to create the File object. This return value is not changed based on the location it is run (results below are for windows, separators are obviously different elsewhere)
File f1 = new File("/some/path");
String path = f1.getPath(); // will return "\some\path"
File dir = new File("/basedir");
File f2 = new File(dir, "/some/path");
path = f2.getPath(); // will return "\basedir\some\path"
File f3 = new File("./some/path");
path = f3.getPath(); // will return ".\some\path"
getAbsolutePath() will resolve the path based on the execution location or drive. So if run from c:\test:
path = f1.getAbsolutePath(); // will return "c:\some\path"
path = f2.getAbsolutePath(); // will return "c:\basedir\some\path"
path = f3.getAbsolutePath(); // will return "c:\test\.\basedir\some\path"
getCanonicalPath() is system dependent. It will resolve the unique location the path represents. So if you have any "."s in the path they will typically be removed.
As to when to use them. It depends on what you are trying to achieve. getPath() is useful for portability. getAbsolutePath() is useful to find the file system location, and getCanonicalPath() is particularly useful to check if two files are the same.
The big thing to get your head around is that the File class tries to represent a view of what Sun like to call "hierarchical pathnames" (basically a path like c:/foo.txt or /usr/muggins). This is why you create files in terms of paths. The operations you are describing are all operations upon this "pathname".
getPath() fetches the path that the File was created with (../foo.txt)
getAbsolutePath() fetches the path that the File was created with, but includes information about the current directory if the path is relative (/usr/bobstuff/../foo.txt)
getCanonicalPath() attempts to fetch a unique representation of the absolute path to the file. This eliminates indirection from ".." and "." references (/usr/foo.txt).
Note I say attempts - in forming a Canonical Path, the VM can throw an IOException. This usually occurs because it is performing some filesystem operations, any one of which could fail.
I find I rarely have need to use getCanonicalPath() but, if given a File with a filename that is in DOS 8.3 format on Windows, such as the java.io.tmpdir System property returns, then this method will return the "full" filename.