I am doing a project that consists of a java server and a web page. I'd like to do that when you delete an object from the web, the server deletes the image asociated with this object. The images of each object are stored inside the images folder inside the web folder. But when i try to delete an image in the server, it says that the file is used by another process,because the thread of the web server is using it (i use grizzly), so I an't delete it.
//save the image
private void saveImage(Eetakemon e){
String base64Image = e.getImage().split(",")[1];
byte[] imageBytes =
javax.xml.bind.DatatypeConverter.parseBase64Binary(base64Image);
File imageFile = new File("WEB\\images\\" + e.getName() + ".png");
try {
BufferedImage bufferedImage = ImageIO.read(new
ByteArrayInputStream(imageBytes));
ImageIO.write(bufferedImage, "png", imageFile);
}
catch(Exception ex){
ex.printStackTrace();
}
}
//delete the image
private void deleteImage(Eetakemon e){
try {
Files.deleteIfExists(Paths.get("WEB\\images\\" + e.getName() +
".png"));
}catch(Exception ex){
ex.printStackTrace();
}
}
The funcions are called inside the create and delete methods respectively
Thank you
You should use a separate folder in your filesystem with read/write access and keep your web server responsible for serving only static content, like static images, HTML,CSS and JS files.
To handle dynamic image files that can eventually be deleted during runtime keep the business logic in a separate service such as a REST API or a simple Servlet.
You can temporarily move the deleted images to a separate folder to be marked for deletion by a later scheduled batch job.
example of a service to delete an image:
public void removeFiles(List<String> fileNames) {
try {
String trashFolderLocation = ConfigurationManager.getInstance().getConfig().getImgFileTrashPath();
String uploadedFileLocation = ConfigurationManager.getInstance().getConfig().getFilePath();
FileUtil.moveFilesToFolder(uploadedFileLocation, trashFolderLocation, fileNames);
} catch(FileException e) {
logException(e);
}
}
In FileUtil:
public static boolean moveFilesToFolder(String locationFrom, String locationTo, List<String> fileNames) throws FileException {
try {
for (String fileName : fileNames) {
File afile = new File(locationFrom + fileName);
if (!afile.renameTo(new File(locationTo + fileName))) {
return false;
}
}
} catch (Exception e) {
throw new FileException(e);
}
return true;
}
You are experiencing a windows property of locking files that are used. You need to locate the process that are using the file and close the resource. This is your only viable option unless you are able to run on a system that doesn't lock files in use. Linux/Unix systems doesn't have this behaviour and they would allow you to delete the file even if it used.
Related
The application KDE Connect allows remotely browsing an Android device from a desktop computer through SFTP. Since Android 4.4, developers don't have write permission to SD cards directly through the filesystem anymore. So I am trying to port the SFTP module using the Storage Access Framework (DocumentFile, etc.)
I am taking the permission with an Intent.ACTION_OPEN_DOCUMENT_TREE and FLAG_GRANT_WRITE_URI_PERMISSION and passing the context to my classes.
I am able to create new empty files, rename files and delete files on the SD card inside my class so I believe I am getting the necessary permissions. However, transferring a file results in an empty file (0 bytes) being created. I can see the transfer taking a certain time and a progress bar on the desktop side, so it doesn't just abort.
Here is the relevant part of the SftpSubsystem class from the Apache SSHD library (see doc here) with my own comments to explain what's going on:
public class SftpSubsystem implements Command, Runnable, SessionAware, FileSystemAware {
// This method receives a buffer from an InputStream and processes it
// according to its type. In this situation, it would also contain
// a block of the file being transferred (4096 bytes)
protected void process(Buffer buffer) {
int type = buffer.getByte();
switch (type) {
case WRITE:
FileHandle fh = getHandleFromString(buffer.getString());
long offset = buffer.getLong();
byte[] data = buffer.getBytes();
fh.write(data, offset);
break;
// other cases
}
}
// This class is a handle to a file (duh) with
// an OutputStream to write and InputStream to read
protected static class FileHandle {
SshFile file;
OutputStream output;
long outputPos;
InputStream input;
long inputPos;
// Method called inside process()
public void write(byte[] data, long offset) throws IOException {
if (output != null && offset != outputPos) {
IoUtils.closeQuietly(output);
output = null;
}
if (output == null) {
// This is called once at the start of the transfer.
// This is what I think I need to rewrite to make
// it work with DocumentFile objects.
output = file.createOutputStream(offset);
}
output.write(data);
outputPos += data.length;
}
}
}
The original implementation of createOutputStream() that I want to rewrite because RandomAccessFile doesn't work with DocumentFile:
public class NativeSshFile implements SshFile {
private File file;
public OutputStream createOutputStream(final long offset)
throws IOException {
// permission check
if (!isWritable()) {
throw new IOException("No write permission : " + file.getName());
}
// move to the appropriate offset and create output stream
final RandomAccessFile raf = new RandomAccessFile(file, "rw");
try {
raf.setLength(offset);
raf.seek(offset);
// The IBM jre needs to have both the stream and the random access file
// objects closed to actually close the file
return new FileOutputStream(raf.getFD()) {
public void close() throws IOException {
super.close();
raf.close();
}
};
} catch (IOException e) {
raf.close();
throw e;
}
}
}
One of the ways I tried to implement it:
class SimpleSftpServer {
static class AndroidSshFile extends NativeSshFile {
// This is the DocumentFile that is stored after
// create() created the empty file
private DocumentFile docFile;
public OutputStream createOutputStream(final long offset) throws IOException {
// permission check
if (!isWritable()) {
throw new IOException("No write permission : " + docFile.getName());
}
ParcelFileDescriptor pfd = context.getContentResolver().openFileDescriptor(docFile.getUri(), "rw");
FileDescriptor fd = pfd.getFileDescriptor();
try {
android.system.Os.lseek(fd, offset, OsConstants.SEEK_SET);
} catch (ErrnoException e) {
Log.e("SimpleSftpServer", "" + e);
return null;
}
return new FileOutputstream(fd, offset);
}
}
}
I also tried a simple (the offset is ignored but it's just a test):
public OutputStream createOutputStream(final long offset) throws IOException {
// permission check
if (!isWritable()) {
throw new IOException("No write permission : " + docFile.getName());
}
return context.getContentResolver().openOutputStream(docFile.getUri());
}
I also tried with a FileChannel and to flush and sync the FileOutputStream.
Any idea why I end up with an empty file?
EDIT: here is a small example of a test I did to just write a new file from an existing file. It works, but this is not what I actually want to do (see code above) but I thought I'd provide an example to show that I understand the basics of how to write to an OutputStream.
private void createDocumentFileFromFile() {
File fileToRead = new File("/storage/0123-4567/lady.m4a");
File fileToWrite = new File("/storage/0123-4567/lady2.m4a");
File dir = fileToWrite.getParentFile();
DocumentFile docDir = DocumentFile.fromTreeUri(context, SimpleSftpServer.externalStorageUri);
try {
DocumentFile createdFile = docDir.createFile(null, fileToWrite.getName());
Uri uriToRead = Uri.fromFile(fileToRead);
InputStream in = context.getContentResolver().openInputStream(uriToRead);
OutputStream out = context.getContentResolver().openOutputStream(createdFile.getUri());
try {
int nbOfBytes = 0;
final int BLOCKSIZE = 4096;
byte[] bytesRead = new byte[BLOCKSIZE];
while (true) {
nbOfBytes = in.read(bytesRead);
if (nbOfBytes == -1) {
break;
}
out.write(bytesRead, 0, nbOfBytes);
}
} finally {
in.close();
out.close();
}
} catch (IOException e) {
}
}
"When using ACTION_OPEN_DOCUMENT_TREE, your app gains access only to the files in the directory that the user selects. You don't have access to other apps' files that reside outside this user-selected directory.
This user-controlled access allows users to choose exactly what content they're comfortable sharing with your app."
This means, you can only read/write/delete the content/meta data of already existing files or in sub directories in the selected directory, the scope that the user accept to be "comfortable" with.
Actually the user granted permmision to a list of Uri's in this folder for ea file/sub directory there is seperate uri permmision.
Now for example if I will try to create new file in the selected Uri using DocumentFile Ill success but if i will try to outputatream new data to this file I will fail because the user did not grant permision to write to this newly created file.
He only granted to write in the directory path level, means create new file here.
So same happens when you try to move/transfer file to other path that does not have permission from the user.
Path can be folder or file and for ea new path the user needs to grant new access.
move file = new path
write to just created file = new path
This is the code
public static void readCharacters() {
try (FileInputStream fi = new FileInputStream("main/characters.dat"); ObjectInputStream os = new ObjectInputStream(fi)) {
characterList = (LinkedList<Character>) os.readObject();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
This is the structure:
And this is the Error
java.io.FileNotFoundException: main\characters.dat (The system cannot find the path specified)
What I want is to include the characters.dat file in my jar, and be able to read and write it while the program runs. Is there a different way to write the path? or to put the .dat file in a different position.
Also the writing method:
public static void writeCharacters() {
try (FileOutputStream fs = new FileOutputStream("main/characters.dat"); ObjectOutputStream os = new ObjectOutputStream(fs)) {
System.out.println("Writing Characters...");
os.writeObject(characterList);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
You can't. You can do one or the other. JAR files are not file systems, and their entries are not files. You can read it with an input stream:
InputStream in = this.getClass().getResourceAsStream("/main/characters.dat");
Check it for null before proceeding.
The jar is for read-only resources. You can use it for the initial file, as a kind of template.
Path path = Paths.get(System.getProperty("user.home") + "/myapp/chars.dat");
Files.mkdirs(path.getParentPath());
if (!Files.exists()) {
try (InputStream in =
Controller.class.getResourceAsStream("/main/characters.dat")) {
Files.copy(in, path);
}
}
The above copies the initial.dat resource from the jar to the user's home "myapp" directory, which is a common solution.
System.getProperty("user.dir") would the running directory. One can also take the jar's path:
URL url = Controller.class.getResource("/main/characters.dat");
String s = url.toExternalForm(); // "jar:file:/.... /xxx.jar!/main/characters.dat"
From that you can also construct the jar's directory. Mind to check Windows, Linux, spaces and such.
URL url = Controller.class.getProtectionDomain().getCodeSource().getLocation();
The solution above risks a NullPointerException, and works a bit differenly running inside the IDE or stand-alone.
Important note:
When using getResourceAsStream, you must start your path by slash /, this specifies the root of your jar, .getResourceAsStream("/file.txt");
In my case my file was a function argument, String filename, I had to do it like this:
InputStream in = this.getClass().getResourceAsStream("/" + filename);
I'm trying to copy files from the assets folder to the device folder using this function:
public static void copyJSON(Context aContext) {
AssetManager assetManager = aContext.getResources().getAssets();
String[] pFiles = null;
try {
pFiles = assetManager.list("ConfigurationFiles");
} catch (IOException e) {
Log.e("tag", "Failed to get asset file list.", e);
}
if (pFiles != null) for (String pJsonFileName : pFiles) {
InputStream tIn = null;
OutputStream tOut = null;
try {
tIn = assetManager.open("ConfigurationFiles" + File.separator + pJsonFileName);
String[] pList = aContext.getFilesDir().list(); //just for test
File pOutFile = new File(aContext.getFilesDir(), pJsonFileName);
tOut = new FileOutputStream(pOutFile);
if (pOutFile.exists()) {
copyFile(tIn, tOut);
}
} catch (IOException e) {
Log.e("tag", "Failed to copy asset file: " + pJsonFileName, e);
} finally {
if (tIn != null) {
try {
tIn.close();
} catch (IOException e) {
Log.e("tag", "Fail closing", e);
}
}
if (tOut != null) {
try {
tOut.close();
} catch (IOException e) {
Log.e("tag", "Fail closing", e);
}
}
}
}
}
If I delete the App and run the code, the variable pList is empty as I expect but the pOutFile.exists()returns true ALWAYS!!.
I don't want to copy them again every time I open my App, and I'm doing this because all my app uses JSON to navigate thru all the screens, so If I change any value in my BBDD a WS send a new JSON file and the App respond in accordance for example a button is no longer needed, so the first time you download my App I copy the original JSON and then if you use the app an if you have internet connection you will download a new JSON file that it is more accurate than the one that is in the Bundle and it will be override, this is because as far as I know I can't change the files that are in the assets folder.
I have read everywhere and all say the same use this:
File pOutFile = new File(aContext.getFilesDir(), pJsonFileName);
And then ask for this:
pOutFile.exists()
I don't know what I'm doing wrong.
Thanks for all your help.
put it this way:
File pOutFile = new File(aContext.getFilesDir(), pJsonFileName);
if (pOutFile.exists()) {
tOut = new FileOutputStream(pOutFile);
copyFile(tIn, tOut);
}
and everything should work fine. Remember the FileOutputStream creates the file it should stream to if possible and non existing
The problem is you're essentially creating a file and then checking if it exists.
try {
tIn = assetManager.open("ConfigurationFiles" + File.separator + pJsonFileName);
String[] pList = aContext.getFilesDir().list(); //just for test
File pOutFile = new File(aContext.getFilesDir(), pJsonFileName);
// See here: you're creating a file right here
tOut = new FileOutputStream(pOutFile);
// And that file will be created in the exact location of the file
// you're trying to check:
if (pOutFile.exists()) { // Will always be true if FileOutputStream was successful
copyFile(tIn, tOut);
}
}
You should instead create your FileOutputStream AFTER you've done your existence check.
Source: http://docs.oracle.com/javase/7/docs/api/java/io/FileOutputStream.html
A file that you have just created without getting an exception always exists. The test is pointless. Remove it.
I have a folder called images under resources folder in eclipse.
And I have multiple images in images folder.
I want to display all the images in my browser by calling a web-service.
I have tried the following code.I am able to retrieve only one image.I want this for multiple images.How can I do this?
ClassLoader classLoader = getClass().getClassLoader();
File file = new File(classLoader.getResource("images/").getPath());
final String[] EXTENSIONS = new String[]{
"png","jpg"// and other formats you need
};
// filter to identify images based on their extensions
final FilenameFilter IMAGE_FILTER = new FilenameFilter()
{
#Override
public boolean accept(final File dir, final String name) {
for (final String ext : EXTENSIONS) {
if (name.endsWith("." + ext)) {
return (true);
}
}
return (false);
}
};
if (file.isDirectory())
{
//list of files I get
for (final File fi : file.listFiles(IMAGE_FILTER))
{
OutputStream out =null;
OutputStream out1 =null;
BufferedImage bi =null;
try
{
System.out.println("file" +fi);
//I get different files from images folder and add that to bufferedImage.
bi= ImageIO.read(fi);
response.setContentType("image/jpeg");
out= response.getOutputStream();
ImageIO.write(bi, "png", out);
ImageIO.write(bi, "jpg", out);
out.close();
}
catch (final IOException e)
{
// handle errors here
e.printStackTrace();
}
}
}
Resources are not files. There is no guarantee that they will even exist in a filesystem, only inside a JAR or WAR file. So using File methods isn't going to work.
In any case just serializing a stream of images to a browser isn't going to work either. You should be generating an HTML page with <img> elements in it, with URLs for the images, and organizing that those URLs are downloadable. Probably using the resource mechanism isn't appropriate in the first place.
The problem:
I'm getting a Base64-Encoded String of raw PDF data from a web service (this data is housed in my String array pdfData). I have to use this data display the PDF in a PDF viewer (I happen to be using the included 'ThinkFree PDF Viewer' since I'm working on an Android application, but lets generalize and say any PDF viewer will do). Note that I'm accessing the 0th element of this array just for testing purposes (to make sure I can at least pull up 1 PDF before writing the code to pull up all the PDFs).
The code is within a class. First the method createFile is called, then intentOpenPDF:
import org.apache.commons.codec.binary.Base64;
File file;
FileOutputStream outputStream;
private byte[] decodedContent;
private String[] pdfData;
private String[] pdfFileName;
public void createFile() {
decodedContent = Base64.decodeBase64(pdfData[0].getBytes());
try {
File path = new File(getFilesDir(), "PDFs");
if (!path.exists()) {
path.mkdirs();
}
file = new File(path, pdfFileName[0]);
outputStream = new FileOutputStream(file);
outputStream.write(decodedContent);
outputStream.close();
}
catch (FileNotFoundException ex) {
ex.printStackTrace();
}
catch (IOException ex) {
ex.printStackTrace();
}
finally {
// Make absolutely certain the outputStream is closed
try {
if (outputStream != null) {
outputStream.close();
}
}
catch (IOException ex) {
ex.printStackTrace();
}
}
}
public void intentOpenPDF() {
// Make sure the file exists before accessing it:
if (file.exists()) {
Uri targetUri = Uri.fromFile(file);
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setDataAndType(targetUri, "application/pdf");
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
}
}
The error:
Error opening file. It does not exist or cannot be read.
I have a break point set inside the conditional statement that checks if the file exists (within the intentOpenPDF method), and it IS passing this check.
The path produced by calling getFilesDir() leads a protected directory (file:///data/data/), where only files created with openFileOutput(String, int) are stored. I am not creating the file this way. The solution in my case is to use getExternalFilesDir(null).getAbsolutePath() instead, which will give you a path a directory internal to the application (/storage/emulated/0/Android/data/). No permissions are required to read or write to this path.
Considering your error message:
It does not exist or cannot be read.
as you verified it exists (first possible cause), it's certainly not readable (second possible cause).