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Method in Java to create a file at a location, creating directories if necessary?
(3 answers)
Closed 1 year ago.
In java, I need to write a string into a new file, like 'c:\test\upload\myfile.txt', if the 'upload' folder is not existing, it will automatically create it. how to do it ? Apache Commons IO has this API ?
File file = new File(...);
file.mkdirs(); //for several levels, without the "s" for one level
FileWriter fileWriter = new FileWriter(file);
fileWriter.write("...");
Creates the directory named by this abstract pathname, including any necessary but nonexistent parent directories. Note that if this operation fails it may have succeeded in creating some of the necessary parent directories.
Returns:
true if and only if the directory was created, along with all necessary parent directories; false otherwise
See File.mkdirs() and File.mkdir()
In addition to the accepted answer, since the question also mentioned the library Apache Common IO, I report in the following a solution by using this nice library:
File file = new File("... the directory path ...");
FileUtils.forceMkdir(file);
This solution uses the class FileUtils, from package org.apache.commons.io and the method forceMkdir, that "Makes a directory, including any necessary but nonexistent parent directories".
new File(fileToSave.getParent()).mkdirs();
It returns a boolean to check if the making succeeded (will fail if the disk is full or if a file exists with the name 'upload', etc)
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getResourceAsStream returns null
(26 answers)
Closed 6 years ago.
I have this peace of code to load a text file inside of a servlet:
String lFileName = mServletContext.getRealPath(mFile);
InputStream lInputStream = mServletContext.getResourceAsStream(lFileName);
InputStream lInputStream2 = mServletContext.getResourceAsStream(mFile);
Both InputStream's are null. I have absolutly no idear why.
The value of mFile is "file.txt".
The value of lFile is "C:\development\workspace\MyGwtApp\war\file.txt".
if I navigate with my explorer to that directory the file file.txt is in it...!
I test my gwt application with the super dev mode.
Compile the gwt app runs without problems.
Do you see the problem?
getResourceAsStream definition
Finds a resource with a given name. The rules for searching resources associated with a given class are implemented by the defining class loader of the class. This method delegates to this object's class loader.
This means that you can read mFile if it exists in your classpath like under WEB-INF/classes. So place your file in your src directory where your java classes exists and look if the file comes to the classes directory and just use its name to get it as resource. Example: filename = "file.txt"
My app needs to get an existing file for processing. Now I have the path of the file in String format, how can I get the File with it? Is it correct to do this:
File fileToSave = new File(dirOfTheFile);
Here dirOfTheFile is the path of the file. If I implement it in this way, will I get the existing file or the system will create another file for me?
That's what you want to do. If the file exists you'll get it. Otherwise you'll create it. You can check whether the file exists by calling fileToSave.exists() on it and act appropriately if it does not.
The new keyword is creating a File object in code, not necessarily a new file on the device.
I would caution you to not use hardcoded paths if you are for dirOfFile. For example, if you're accessing external storage, call Environment.getExternalStorageDirectory() instead of hardcoding /sdcard.
The File object is just a reference to a file (a wrapper around the path of the file); creating a new File object does not actually create or read the file; to do that, use FileInputStream to read, FileOutputStream to write, or the various File helper methods (like exists(), createNewFile(), etc.) for example to actually perform operations on the path in question. Note that, as others have pointed out, you should use one of the utilities provided by the system to locate directories on the internal or external storage, depending on where you want your files.
try this..
File fileToSave = new File(dirOfTheFile);
if(fileToSave.exists())
{
// the file exists. use it
} else {
// create file here
}
if parent folder is not there you may have to call fileToSave.getParentFile().mkdirs() to create parent folders
My resources folder inside my jar includes a directory with several binary files. I am attempting to use this code to extract them:
try(InputStream is = ExternalHTMLThumbnail.class.getResourceAsStream("/wkhtmltoimage")) {
Files.copy(is, Paths.get("/home/dan/wkhtmltoimage");
}
This is throwing the error
java.nio.file.NoSuchFileException: /home/dan/wkhtmltoimage
Which comes from
if (errno() == UnixConstants.ENOENT)
return new NoSuchFileException(file, other, null);
in UnixException.java. Even though in Files.java the correct options are passed:
ostream = newOutputStream(target, StandardOpenOption.CREATE_NEW,
StandardOpenOption.WRITE);
from Files.copy. Of course there's not! That's why I'm trying to make it. I don't yet understand Path and Files enough to do this right. What's the best way to extract the directory and all its contents?
Confused because the docs for Files.copy claims
By default, the copy fails if the target file already exists or is a symbolic link
(Apparently it fails if the target file doesn't exist as well?)
And lists the possible exceptions, and NoSuchFileException is not one of them.
If you're using Guava:
URL url = Resources.getResource(ExternalHTMLThumbnail.class, "wkhtmltoimage");
byte[] bytes = Resources.toByteArray(url);
Files.write(bytes, new File("/my/path/myFile"));
You could of course just chain that all into one line; I declared the variables to make it more readable.
The file that does not exist may actually be the directory you're trying to create the file in.
/home/dan/wkhtmltoimage
Does /home/dan exist? Probably not if you're on a Mac.
This is the problem I have: If part or all of the path does not already exist, the server should create additional directories as necessary in the hierarchy and then create a new file as above.
Files.createDirectories(path);
That's what I am currently using, but it does not create the end file. For example is the path="/hello/test.html" it will create a directory called "hello" and one called "test.html", I want the test.html to be a file. How can I do that?
This is what I did to solve this "problem" or misuse of the libraries.
Files.createDirectories(path.getParent());
Files.createFile(path);
The first line will get the parent directory, so lets say this is what I want to create "/a/b/c/hello.txt", the parent directory will be "/a/b/c/".
The second like will create the file within that directory.
Have you looked at the javadoc? createDirectories only creates... directories. If you're intent on using Files.createDirectories, parse off the file name, call createDirectories passing only the path portion, then create a new file passing the entire path. Otherwise this is a better approach.
Files.createDirectories(path.substring(0, path.lastIndexOf(File.separator)+1));
File yourFile = new File(path);
you can parse the 'path' variable to isolate the file and the directory using delimiter as '/', and do File file = new File(parsedPath); This would work only when you know that you ALWAYS pass the file name at the end of it.
If you know when you are a) creating a directory b) creating a directory and file, you can pass the boolean variable that would describe if file needs to be created or not.
File testDir = new File("C:\temp\test");
testDir.createNewFile();
As I understand it, the above will create a directory called test in the directory c:\temp
File testDir = new File("C:\temp\test.dir");
testDir.createNewFile();
As I understand it, the above will create a file called test.dir in the directory c:\temp
What should I be doing to the code above if I wish for test.dir to actually be a directory?
No, the first one will create a regular file - after all, that's what you asked it to do:
Atomically creates a new, empty file named by this abstract pathname if and only if a file with this name does not yet exist. The check for the existence of the file and the creation of the file if it does not exist are a single operation that is atomic with respect to all other filesystem activities that might affect the file.
Nothing there says it will create a directory. You'll want to escape the backslashes though, or it's trying to find C:<tab>emp<tab>est
If you want to create a directory, use File.mkdir or File.mkdirs(). You'll still need to escape the backslashes:
File testDir = new File("C:\\temp\\test.dir");
bool created = testDir.mkdir();
(Use mkdirs to create parent directories as well.) The return value tells you whether or not it actually created a directory.
That's not true.
File.createFile() will create a file.
File.mkdir() creates a directory.
http://download.oracle.com/javase/6/docs/api/java/io/File.html
File testDir = new File("C:\temp\test");
testDir.createNewFile();
As I understand it, the above will
create a directory called test in the
directory c:\temp
Wrong - it will create file called "test". Files do not have to have a "filename extension".
To create a directory:
testDir.mkdir();
BTW, this kind of question is most easily and quickly answered by looking at the API doc. Do yourself a favor and get familiar with it.