First I'm writing the excel file in a temporary location then I'm downloading it from that location. Here is the code:
Here I'm writing excel into some temporary location and returning the location of that file:
public String parseExcel(Map<String, List<String>> data) {
Workbook workbook = new XSSFWorkbook();
Sheet sheet1 = workbook.createSheet("Sheet1");
.
.
.
var tmplocation = File.createTempFile("SampleTemplate", ".xlsx");
FileOutputStream fileOut = new FileOutputStream(tmplocation);
workbook.write(fileOut);
fileOut.close();
return tmplocation.getPath();
}
And here I'm downloading that file from that location:
try {
filePath = parseExcel(data);
file = new File(filePath);
return Cors.add(request, Response.ok(file).header("Content-Disposition",
"attachment;filename=\"SampleTemplate.xlsx\"").header("Content-Length ", file.length())).allowAllOrigins().auth().build();
} catch() {
.
.
.
}
To delete the temporary file I added finally block and in finally block I'm getting the file, but it didn't worked. It said FileNotFound Exception
How can I delete this temporary file after the successful download of the file?
The deleteIfExists() method of java.nio.file.Files can help you.
Deletes a file if it exists.
As with the delete(Path) method, an implementation may need to examine the file to determine if the file is a directory. Consequently this method may not be atomic with respect to other file system operations. If the file is a symbolic link, then the symbolic link itself, not the final target of the link, is deleted.
If the file is a directory then the directory must be empty. In some implementations a directory has entries for special files or links that are created when the directory is created. In such implementations a directory is considered empty when only the special entries exist.
On some operating systems it may not be possible to remove a file when it is open and in use by this Java virtual machine or other programs.
You may also wish to use createTempFile() to create your file.
For reference:
Java better way to delete file if exists
Java Tutorials - Deleting a File or Directory
You want to delete a file? You might think of file.delete ();.
You can find that it actually exists by reading the documentation for the File class and scanning the list of methods. In doing so, you will see things that you will remember later on, so it is a great way to expand knowledge.
Documentation is useful.
If you use an IDE like Eclipse, you can get a context-sensitive menu of suggestions, usually a list of possible methods you might use.
Related
Although the Title isn't very understandable I do have a simple issue. So i'm trying to write some code in a Processing Sketch (https://processing.org/) which can count how many files are in a document. The problem is, is that it doesn't accept the variable type.
File folder = File("My File Path");
folder.listFiles().size;
It says the function File(String) doesn't exist. When I try to put the file path without quation marks, it still doesn't work!
If you have a solution then please use a functioning example so that I know how it works. Thanks for any help!
As Joakim Danielson says it is constructor so you need to use new keyword.
Below code will work for you.
File folder = new File("My File Path");
int fileLength = folder.listFiles().length;
It's a constructor so you need to use new
File folder = new File("My File Path");
//To get the number of files in the folder
folder.listFiles().length;
Assuming the "My File Path" folder is inside your sketch you need to provide the path to your sketch. Luckily Processing already provides a helper function: sketchPath()
Here's an example:
File folder = new File(sketchPath("My File Path"));
println("folder.exists: " + folder.exists());
if(folder.exists()){
println(folder.listFiles().length + " files and/or directories");
}else{
println("folder does not exist, double check the path");
}
Bare in mind there's also a dataPath() function which points to a folder named data in your sketch folder. The data folder is typically used for storing external data (e.g. assets (raster or vector images/Processing font files) or raw data (binary/text/csv/xml/json/etc.)). This is useful to separate your sketch source files from the data to be loaded/accessed by your sketch.
Also, Processing has a few utility functions for listing files and folders.
Be sure to check out Processing > Examples > Topics > File IO > DirectoryList
The example includes less documented functions such as listFiles() (which returns an array of java.io.File objects based on the filters set) or listPaths (which returns an array of String objects: just the paths).
The options and filters are quite handy, for example if you want to list directories only and ignore files you can simply write simply like:
println("directories: " + listFiles(sketchPath("My File Path"),"directories").length);
For example if want to list all the wav files in a data/audio directory inside the sketch you can use:
File[] files = listFiles(dataPath("audio"), "files", "extension=wav");
This will ignore directories and any other file that does not have .wav extension.
To make this answer complete, here are a few more details on the options for listFiles/listPaths from Processing's source code:
"relative" -> no effect with the Files version, but important for listPaths
"recursive"-> traverse nested directories
"extension=js" or "extensions=js|csv|txt" (no dot)
"directories" -> only directories
"files" -> only files
"hidden" -> include hidden files (prefixed with .) disabled by default
I decided to post a new question on this since none of the existing posts lead to me a solution. Mine is a Spring Boot application and here is the service:
public String fetchPrediction(MultipartFile file) throws IOException, InterruptedException {
File convFile = new File( System.getProperty("user.dir")+"/"+file.getOriginalFilename());
convFile.setWritable(true);
file.transferTo(convFile);
INDArray array = new CustomerLossPrediction().generateOutput(convFile);
Files.delete(Paths.get(convFile.getPath()));
return array.toString();
}
File deletion isn't happening and it gets stored at user home directory:
Found that the file is being used by the Java process. How can I delete this file once execution is completed? Is there a better approach here rather than writing to a file? Some of you would bring up writing to OutputStream here, but note that I need to work with MultipartFile in order to have file upload functionality.
I don't know if that's possible but I think you can rename the file to a randomly generated string then afterwards lock, read, unlock then delete the renamed file. In theory, another program could guess the filename and read the file just after it's unlocked but before it is deleted. But in practice, you'll probably be fine.
Can anyone help me how to change a line in a file using java IO function. The file is located at SDCard. I have tried some solution from different blog, but failed.
I need to change one attribute wpa_oper_channel=1 to 2,3,4..... as user demand in the file sdcard/sample.txt.
I have also tried using SED command, but still not working. Please suggest if there any solution using java IO function.
The Command I have used using SED :
sed -i 's/wpa_oper_channel=[0-9]\\+/wpa_oper_channel=7/' sample.txt
If your configuration file is in the form of a Properties file. This means each line is in a format of key=value. You can easily read, modify and write it. Here is an example, I assume you have no problem with reading and writing a file through streams.
File sdcard = Environment.getExternalStorageDirectory();
File file = new File(sdcard,"sample.txt");
InputStream is = new FileInputStream(file); // Read your existing file
Properties props = new Properties();
props.load(is);
props.setProperty("wpa_oper_channel", "4");
OutputStream out = new FileOutputStream(file); // Your output file stream
prop.store(output, null); // Save your properties file without header
By doing this, you may lose if there is another type of line like comments or else.
Update
I updated to source code. But still you need to get read and write permission.
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
I haven't test the code, It will work with some exception handling. If it is not work please specify your error.
You just have to
read the file's content into memory (there are millions of examples on how to do that with java),
change the content (finding the position could be done using e.g. indexOf("wpa_oper_channel="))
write the content back to the file (there are millions of examples for that too)
What android do you use?
From android 4.4+ user haven't access to edit and remove files from SD Card. You must copy them to external storage and use there. See this link - http://code.google.com/p/android/issues/detail?id=67570
I'm trying to create a directory hierarchy and then copy a file from my assets into the newly created directory. I've used the code samples offered here on stackoverflow but I'm not getting anywhere. Essentially my code goes like this:
InputStream in = getAssets.open(mydb.sqlite);
File dir = new File("/data/data/my.package/databases/");
dir.mkdirs();
out = new FileOutputStream("/data/data/my.package/databases/mydb.sqlite");
while ((len = in.read(buffer)) > 0)
{
out.write(buffer, 0, len);
}
out.flush();
out.close();
in.close
This is all done within the main activity on first launch and of course should only be done once. Before the code runs, the only directory that exists is /data/. Yes, it is a database file but that shouldn't matter at this point since I'm just copying the file and haven't yet tried to access it with the database code.
The code doesn't throw any exceptions, and dir.mkdirs() returns true. Regardless, the directories are not created and the file is not copied. I have added the permissions line for WRITE_EXTERNAL_STORAGE to my manifest as has been suggested in several places, FWIW. I can step through the code and everything appears to be fine. But of course it's not.
What do I need to be looking for here? File permissions problems? Why does the code think everything is there (ie, when it gets to the copy code, it doesn't throw FileNotFoundException) but in reality there's nothing on the file system?
Edit: Here's what I've learned. getDir() creates the directory in /data/data/my.package/app_*. Not sure why it uses this prefix on the directory name. This won't work if you need to put something in a standard location such as databases/ or files/.
Use openFileOutput instead as /data/data is internal storage and you should only use the Android APIs to get a file handle there. See: http://developer.android.com/guide/topics/data/data-storage.html#filesInternal
Edit:
/data/data/my.package is handled by openFileOutput/getDir so you would create your directory with getDir('databases',MODE_PRIVATE) and create your file there.
Edit2:
From getDir documentation:
You can use the returned File object to create and access files in this directory.
I followed this tutorial for uploading a file in my JSF2 application.
The application works fine but I am unhappy with one aspect.
While rebuilding the request, the File sent via request is saved somewhere on the disk.
Even though the file is saved I need to rename the file with a name which is available after entering the Managed Bean containing the action method.
Therefore I decided to create a new file with de desired name, copy the already saved file, and then delete the unneeded one.
private File uploadFile;
//...
try {
BufferedWriter bw = new BufferedWriter(new FileWriter(newFile));
BufferedReader br = new BufferedReader(new FileReader(uploadFile));
String line = "";
while ((line = br.readLine()) != null){
bw.write(line);
}
} catch (Exception e){}
The new file appears in the desired location but this error is thrown when I'm trying to open the file: "Invalid or unsupported PNG file"
These are my questions:
Is there a better way to solve this problem?
Is this solution the best way to upload a picture? Is there a reason to save the file before the business logic when there may be need to resize the picture or the desired name is not available yet.
LE:
I know abot this tutorial as well but I'm trying to do this mojarra only.
There is a rename method built into java.io.File object already, I'd be surprised if it didn't work for your situation.
public boolean renameTo(File dest)
Renames the file denoted by this abstract pathname.
Many aspects of the behavior of this method are inherently platform-dependent:
The rename operation might not be able to move a file from one filesystem to
another, it might not be atomic, and it might not succeed if a file with the
destination abstract pathname already exists. The return value should always
be checked to make sure that the rename operation was successful.
You can also check if a file exists before saving it, and you can use the ImageIO class to do validations on the uploaded file before performing the initial save.
Don't use Reader and Writer when you deal with binary files like images. Use streams: FileInputStream and FileOutputStream. And the best variant is to use #Perception solution with renameTo method.
Readers read file as if it consists of characters (e.g. txt, properties, yaml files). Image files are not characters, they are binary and you must use streams for that.