I am trying to get the following code to work properly. It always prints the output from the catch block, even though the output that is only printed if the file exists, is printed.
String outputFile = "/home/picImg.jpg";
File outFile = new File(outputFile);
if(outFile.exists)
newStatus(" File does indeed exist");
FileOutputStream fos;
try {
fos = new FileOutputStream(outFile);
fos.write(response);
fos.close();
return outputFile;
} catch (FileNotFoundException ex) {
newStatus("Error: Couldn't find local picture!");
return null;
}
In the code response is a byte[] containig a .jpg image from a URL. Overall I am trying to download an image from a URL and save it to the local file system and return the path. I think the issue has to do with read/write permissions within /home/. I chose to write the file there because I'm lazy and didn't want to find the username to find the path /home/USER/Documents. I think I need to do this now.
I notice in the terminal I can do cd ~ and get to /home/USER/. Is there a "path shortcut" I can use within the file name so that I can read/write in a folder that has those permissions?
No. The ~ is expanded by the shell. In Java File.exists() is a method, you can use File.separatorChar and you can get a user's home folder with System property "user.home" like
String outputFile = System.getProperty("user.home") + File.separatorChar
+ "picImg.jpg";
File outFile = new File(outputFile);
if (outFile.exists())
Edit
Also, as #StephenP notes below, you might also use File(File parent, String child) to construct the File
File outFile = new File(System.getProperty("user.home"), "picImg.jpg");
if (outFile.exists())
~ expansion is a function of your shell and means nothing special for the file system. Look for Java System Properties "user.home"
Java provides a System property to get the user home directory: System.getProperty("user.home");.
The advantage of this is, that it works for every operating system that can run the Java virtual machine.
More about System properties: Link.
Related
i upload a csv file from client side and i want to create this file in server side.
Here is my function
public void uploadFile(FileUploadEvent e) throws IOException{
UploadedFile uploadedCsv=e.getFile();
String filePath="//ipAdress:/home/cg/Temp/input/ressource.csv";
byte[] bytes=null;
if(uploadedCsv != null){
bytes=uploadedCsv.getContents();
BufferedOutputStream stream = new BufferedOutputStream(new FileOutputStream(new File(filePath)));
String filename = FilenameUtils.getName(uploadedCsv.getFileName());
stream.write(bytes);
stream.close();
}
}
When I want to write the file I get this exception (No such file or directory)
SEVERE: java.io.FileNotFoundException: /ipAdress:/home/cg/Temp/input/ressource.csv (No such file or directory)
Knowing that the / home / cg / Temp / input path is created on the server.
Could you try:
String filePath="////ipAdress/home/cg/Temp/input/ressource.csv";
Instead of:
String filePath="//ipAdress:/home/cg/Temp/input/ressource.csv";
And this:
new File(new URI(filePath))
Instead of:
new File(filePath)
Or you can use jcif API How can I open a UNC path from Linux in Java?
I would use the <file>.mkdirs(); at one level above the file itself.
So do String filePath="//ipAdress:/home/cg/Temp/input
File directory = new File(filePath);
directory.mkdirs();
You can then make the file
File tempFile = new File(directory + "/ressource.csv);
Or a cleaner solution all around is just use Files.createTempFile(prefix, suffix) this will create a file in the temp directory of the system.
The reason that your code does not work is that you are trying to use a UNC pathname on Linux. Linux does not support UNC pathnames ... natively. They are a Windows-ism.
Here's your example
"//ipAdress:/home/cg/Temp/input/ressource.csv";
If you try to use that on Linux, the OS will look for a directory in the root directory of the file system. The directory it will look for will have the name ipaddress: ... noting that there is a colon in the directory name!
That will most likely fail ... because no directory with that name exists in the / directory.. And the exception message you are getting is consistent with this diagnosis.
If you are doing this because you are trying to push files out to other systems then you are going to do it some other way. For example:
Use NFS and mount the other system's file systems on the server.
Use a Java implementation of UNC names; e.g. How can I open a UNC path from Linux in Java?
(Which ever way you do it, there are security issues to consider!)
trying this new File(new URI(filePath)) instead of new File(filePath) i get this erreur. SEVERE: java.lang.IllegalArgumentException: URI is not absolute
It won't work. A UNC name is NOT a valid URL or URI.
I have found a solution for this problem, but it's not smart and still and it works
String fileName="ressource.csv";
File f = new File(System.getProperty("user.home") + "/Temp/input",fileName);
if (f.exists() && !f.canWrite())
throw new IOException("erreur " + f.getAbsolutePath());
if (!f.exists())
Files.createFile(f.toPath());
if (!f.isFile()) {
f.createNewFile(); // Exception here
} else {
f.setLastModified(System.currentTimeMillis());
}
Pending a more intelligent solution
This may be a stupid question, but I have to ask because I couldn't find any proper solution.
I am new to Eclipse. I created a Dynamic Web project in Eclipse, In this, I write a simple code to create a text file, Only file name is specified Not the path that where to create, After successful execution, i could not find my text file in my project folder.
If path is specified in the code, I can find the text file in specified directory, My Question is where i can find my text file if i am not specify a path ?
And my code is
try {
FileWriter outFile = new FileWriter("user_details.txt", true);
PrintWriter out1 = new PrintWriter(outFile);
out1.append(request.getParameter("un"));
out1.println();
out1.append(request.getParameter("pw"));
out1.close();
outFile.close();
System.out.println("file created");
} catch(Exception e) {
System.out.println("error in writing a file"+e);
}
I edited my code with following lines,
String path = new File("user_details.txt").getAbsolutePath();
System.out.println(path);
The path that i got is below
D:\Android\eclipse_JE\eclipse\user_details.txt
Why i got it in the eclipse folder ?
Then,
How can i create a text file in my web app, if this is not the right way to create a textfile ?
The file is located in the actual working directory of your application server. Do a
System.out.println(new File("").getAbsolutPath());
and you'll find the location.
However this is not a good idea to write files in web application like this, because first you never know where it is and second you never know whether you write privilege on it.
You need to specify some filesystem root for your application by passing it as init-parameter and use it as parent for everything you need to do on the filesystem. Check this answer to a similar Question.
You could then create your file like this:
String fsroot = getServletContext().getInitParameter("fsroot")
File ud = new File(fsroot, "user_details.txt");
FileWriter outFile = new FileWriter(ud, true);
You may try the getAbsolutePath() method.
String newFile = new File("Demo.txt").getAbsolutePath();
It will show the location where the files will be created.
I need to create temporary directory but I'm always getting access denied when I try to create a file into the temporary directory.
java.io.FileNotFoundException: C:\tmpDir7504230706415790917 (Access Denied)
here's my code:
public static File createTempDir() throws IOException {
File temp = File.createTempFile("tmpDir", "", new File("C:/"));
temp.delete();
temp.mkdir();
return temp;
}
public File createFile(InputStream inputStream, File tmpDir ) {
File file = null;
if (tmpDir.isDirectory()) {
try {
file = new File(tmpDir.getAbsolutePath());
// write the inputStream to a FileOutputStream
OutputStream out = new FileOutputStream(file);
int read = 0;
byte[] bytes = new byte[1024];
while ((read = inputStream.read(bytes)) != -1) {
out.write(bytes, 0, read);
}
inputStream.close();
out.flush();
out.close();
System.out.println("New file created!");
} catch (IOException e) {
System.out.println(e.getMessage());
}
}
return file;
}
I'm working on a web application and I'm using tomcat. Is there a way to create temporary file on tomcat server memory? I know that's bizarre, but I don't know ... maybe it's possible.
You could use Tomcat's temp folder.
If you use
<%=System.getProperty("java.io.tmpdir")%>
in a JSP you can get path to it.
This line in your code says create a file whose name starts with text "tmpDir" in the directory "C:\". That is not what you want.
File temp = File.createTempFile("tmpDir","",new File("C:/"));
The operating system is properly disallowing that because C:\ is a protected directory. Use the following instead:
File temp = File.createTempFile("tmp",null);
This will let Java determine the appropriate temporary directory. Your file will have the simple prefix "tmp" followed by some random text. You can change "tmp" to anything meaningful for your app, in case you need to manually clean out these temp files and you want to be able to quickly identify them.
You usually cannot write onto C:\ directly due to the default permission setting. I sometime have permission issue for doing so. However, you can write your temporary file in your user folder. Usually, this is C:\Documents and Settings\UserName\ on XP or C:\Users\UserName\ on vista and Windows 7. A tool called SystemUtils from Apache Lang can be very useful if you want to get the home directory depending on OS platform.
For example:
SystemUtils.getUserDir();
SystemUtils.getUserHome();
Update
Also, you create a temp file object but you call mkdir to make it into a directory and try to write your file to that directory object. You can only write a file into a directory but not on the directory itself. To solve this problem, either don't call temp.mkdir(); or change this file=new File(tmpDir.getAbsolutePath()); to file=new File(tmpDir, "sometempname");
On Linux with tomcat7 installation:
So if you are running web application this is the temp directory Tomcat uses for the creation of temporary files.
TOMCAT_HOME/temp
In my case TOMCAT_HOME => /usr/share/tomcat7
If you are running Java program without tomcat, by default it uses /tmp directory.
Not sure if it affects but i ran this command too.
chmod 777 on TOMCAT_HOME/temp
FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_WORLD_READABLE);
fos.write(string.getBytes());
fos.close();
When trying to delete one of those files, this is what I use, but it's returning false.
String tag = v.getTag().toString();
File file = new File(System.getProperty("user.dir")+"/"+tag);
String s = new Boolean (file.exists()).toString();
Toast.makeText(getApplicationContext(), s, 1500).show();
file.delete();
How can I overcome this problem?
Use getFileStreamPath(FILENAME) to find your file. From the docs:
Returns the absolute path on the filesystem where a file created with openFileOutput(String, int) is stored.
Your current working directory.
To help diagnose the problem, use file.getAbsolutePath() to see the full path.
It could also be a permissions problem, if you're trying to delete from another application. If so, you may need to change to MODE_WORLD_WRITEABLE (insecure), or restructure your code so the create and delete are called by the same app.
EDIT: That was mostly incorrect. I didn't realize that openFileOutput didn't use the current working directory.
Use same contents as 'FILENAME' variable in your first snippet in the second snippet while trying to delete.
String RootDir = Environment.getExternalStorageDirectory()
+ File.separator + "Video";
File RootFile = new File(RootDir);
RootFile.mkdir();
FileOutputStream f = new FileOutputStream(new File(RootFile, "Sample.mp4"));
i used this code to save the video files to non-default location. Hope this will be useful to you.By default it is storing in sd card
For each application the Android system creates a "data/data/package of the application" directory.
Files are saved in the "files" folder under this directory
to change the default directory the above code will be used
the default working directory can be displayed using fileobject.getAbsolutePath()
I want to create a folder in ex. my desktop in Mac OS X
I try to use this code, instead of Mymac is my name of course:)
String path="/Users/Mymac/Desktop";
String house = "My_home";
File file=new File(path);
if(!file.exists())
file.mkdirs(); // or file.mkdir()
file=new File(path + "/" + house);
try {
if(file.createNewFile())
{
}
} catch (IOException ex) {
ex.printStackTrace();
}
Do you know how I could create a new folder?
And another thing is when I want to create a folder in the directory where my code is, do you know how I could write that? I have tried
String path="./";
String path="::MyVolume";
String path=".";
A platform-independent way:
File rootDir = File.listRoots()[0];
File dir = new File(new File(new File(rootDir, "Users"), "Mymac"), "Desktop");
if (!dir.exists()){
dir.mkdirs();
}
Your code is ok and will work. Perhaps you have a typo in your username in your file-path ("Mymac"), so you don't see the changes, since they go to another folder.
Running this code on my machine works fine and gives the expected result.
To make your code platform-independant, you can build your file-path with the following trick:
File path = new File(File.listRoots()[0], "Users" + System.getProperty("file.separator") + "Mymac" + System.getProperty("file.separator") + "Desktop"));
If "My_home" should be a folder and not a file, you have to change the file.createNewFile() - command. More detailed information you'll find in the answer of Thomas.
To find the folder/directory where one of your classes is (assuming they are not in a Jar), and then to create a subfolder there:
String resource = MyClass.class.getName().replace(".", File.separator) + ".class";
URL fileURL = ClassLoader.getSystemClassLoader().getResource(resource);
String path = new File(fileURL.toURI()).getParent();
String mySubFolder = "subFolder";
File newDir = new File(path + File.separator + mySubFolder);
boolean success = newDir.mkdir();
(The code above could be made more compact, I listed it more verbosely to demonstrate all the steps.) Of course, you need to be concerned about permission issues. Make sure that the user which is running java has permission to create a new folder.
Use file.mkdir() or file.mkdirs() instead of file.createNewFile() and it should work, if you have permission to create new folders and files.
mkdirs() will create the subfolders if they don't exist, mkdir() won't.
To create a directory in your base directory (the one you start your application from), just provide a relative path name: new File("mydir").mkdir();
Edit: to make file handling easier, I'd suggest you also have a look at Apache Commons' FilenameUtils and FileUtils.