in one of the activities when a button is pressed i want to create a file on the extran storage. so i wrote
the below code to do so.
but in the end the file is created but empty..why?
code:
public void tx(byte[] data) {
Log.w(TAG, CSubTag.bullet("tx"));
File file = new File(Environment.getExternalStorageDirectory() + File.separator + "test.txt");
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
try {
OutputStream os = new FileOutputStream(file);
BufferedOutputStream bos = new BufferedOutputStream(os);
try {
bos.write("data_stream".getBytes());
} catch (IOException e) {
e.printStackTrace();
}
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}
Please close the OutputStream and BufferedOutputStream inside finally block. Otherwise, the data will not be written.
Related
I want to save all elements of a HashMap in a file. To do this I wrote following code with the help of some google searches:
public void saveCalendars() {
try {FileOutputStream fos = new FileOutputStream(CALENDARPATH_STRING);
ObjectOutputStream oos = new ObjectOutputStream(fos);
for(Calendar elementCalendar : calendarRegister.values()) {
oos.writeObject(elementCalendar);
}
oos.close();
fos.close();
} catch (FileNotFoundException e) {
System.out.println("File not found");
try {FileOutputStream fos = new FileOutputStream(new File(CALENDARPATH_STRING));
ObjectOutputStream oos = new ObjectOutputStream(fos);
for(Calendar elementCalendar : calendarRegister.values()) {
oos.writeObject(elementCalendar);
}
oos.close();
fos.close();
} catch (IOException ex) {
System.out.println("Creating: Error initializing stream");
}
} catch (IOException e) {
System.out.println("Save: Error initializing stream");
}
}
With final static String CALENDARPATH_STRING = "C:\\Windows\\calendars.dat";.
I thought that I simply could use the same Code but with FileOutputStream fos = new FileOutputStream(new File(CALENDARPATH_STRING)); if the file hasn't been created yet to create one.
Unfortunately, it doesn't work. It's the firs time, that a make such saving stuff, so maybe you can help me.
A couple of suggestions:
Use File.createNewFile to create a new file and verify it's result
Use try-with-resources when dealing with IO stuff (I assume you use > JDK 7). You can read more about this feature on official site.
You can avoid duplications:
File calendarFile = new File(CALENDARPATH_STRING);
try {
if(calendarFile.createNewFile()) {
System.out.println("File not found. New file was created");
}
} catch (IOException e) {
System.out.printf("Can not create file %s\n", CALENDARPATH_STRING);
}
try(FileOutputStream fos = new FileOutputStream(calendarFile);
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
for(Calendar elementCalendar : calendarRegister.values()) {
oos.writeObject(elementCalendar);
}
} catch (IOException e) {
System.out.println("Save: Error initializing stream");
}
Well, I can see that there is an issue with the path of your file CALENDAR_PATH_STRING
and use new File(CALENDAR_PATH_STRING) it would create a new file if the particular file was not found. Also in local I can see it is working.
public void saveCalendars(Map<String, Calendar> calendarRegister) {
try (FileOutputStream fos = new FileOutputStream(new File(CALENDAR_PATH_STRING));
ObjectOutputStream oos = new ObjectOutputStream(fos)) {
for (Calendar elementCalendar : calendarRegister.values()) {
oos.writeObject(elementCalendar);
}
} catch (IOException e) {
System.out.println("Creating: Error initializing stream");
}
}
I have this code:
private void save(Bitmap bitmap) {
try {
FileOutputStream fos = new FileOutputStream(path);
bitmap.compress(Bitmap.CompressFormat.JPEG, COMPRESSION_QUALITY, fos);
fos.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
Do I need to close the FileOutputStream in FileNotFoundException catch block?
If that exception is thrown means that file could not be opened so I think that it would not be necessary. However, I think it would be nice to do it in IOException catch block.
Could it cause any memory leak error or something similar if I don't do it?
Thanks.
If you are working in Java 7 or above you should use a try with resources and let the system decide.
private void save(Bitmap bitmap) {
try (FileOutputStream fos = new FileOutputStream(path)) {
bitmap.compress(Bitmap.CompressFormat.JPEG, COMPRESSION_QUALITY, fos);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
If not then just ensure that the stream is not null first and do it in a finally.
private void save(Bitmap bitmap) {
FileOutputStream fos = null;
try {
fos = new FileOutputStream(path);
bitmap.compress(Bitmap.CompressFormat.JPEG, COMPRESSION_QUALITY, fos);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fos != null) {
fos.close();
}
}
}
There is nothing to close. The FileOutputStream constructor threw an exception; the stream was never constructed; the fos variable has never been assigned; and it is out of scope in the catch block.
You should always close the file once you have finished to read or write. Otherwise you will keep the resource busy and in general could be a problem.
If you modify your code in this way you will not have to care about close the file and java will think about it.
private void save(Bitmap bitmap) {
try(FileOutputStream fos = new FileOutputStream(path)) {
bitmap.compress(Bitmap.CompressFormat.JPEG, COMPRESSION_QUALITY, fos);
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
I am trying to create kmz file from kml file on the fly and render it as a stream of bytes in web application.
But when I downloaded generated kmz file, I couldn't open it using archive manager on Ubuntu.
I view similar questions on this site, but it don't work.
Can someone help me and explain what I do wrong?!
This is my code.
#Public public void retrieveKmlInOldFormat() {
File file = new File(Play.applicationPath+"/"+Play.configuration.getProperty("web.content", "../bspb-web")+"/map/map.kml");
String kmlFileContent = null;
try {
String kmlUrl = file.toURI().toURL().toString();
kmlFileContent = BSPBKml2OldFormatConverter.toOldKml(
kmlParserLocal.load(kmlUrl));
} catch (MalformedURLException e) {
e.printStackTrace();
}
String zippedFileName = "old_fmt_map.kmz";
String zippedKml = compressKmlFile(kmlFileContent,zippedFileName);
response.setContentTypeIfNotSet("application/vnd.google-earth.kmz");
renderBinary(new ByteArrayInputStream(zippedKml.getBytes()),zippedFileName);
return;
}
Compress method code:
private String compressKmlFile(String kmlFileContent,String zipEntryName){
String zippedContent = null;
ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
ZipOutputStream zipStream = new ZipOutputStream(new
BufferedOutputStream(byteStream));
ZipEntry zipEntry = null;
zipEntry = new ZipEntry("doc.kml");
try {
zipEntry.setSize(kmlFileContent.getBytes("UTF-8").length);
zipStream.putNextEntry(zipEntry);
zipStream.write(kmlFileContent.getBytes("UTF-8"));
zipStream.closeEntry();
zippedContent = new String(byteStream.toByteArray(),"UTF-8");
} catch (IOException e) {
logger.error("Error while zipping kml file content");
}
finally {
try {
byteStream.close();
zipStream.close();
} catch (IOException e) {
logger.error(e.getMessage());
}
}
return zippedContent;
}
The problem is about downloaded corrupted kmz archive. This problem can be resolved by using output stream of http response as constructor argument for ZipOutputStream class.
Solution is in this code.
#Public public void retrieveKmlInOldFormat(){
File file = new File(Play.applicationPath+"/"+Play.configuration.getProperty("web.content", "../bspb-web")+"/map/map.kml");
String kmlFileContent = null;
try {
String kmlUrl = file.toURI().toURL().toString();
kmlFileContent = BSPBKml2OldFormatConverter.toOldKml(kmlParserLocal.load(kmlUrl));
} catch (MalformedURLException e) {
e.printStackTrace();
}
response.setContentTypeIfNotSet("application/vnd.google-earth.kmz");
response.setHeader("Content-Disposition", "attachment; filename=\"old_fmt_map.kmz\"");
renderAsKmz(response, kmlFileContent,"old_fmt_map.kml");
return;
}
private void renderAsKmz(Response response,String kmlFileContent,String zipEntryName){
ZipOutputStream zipStream = new ZipOutputStream(response.out);
ZipEntry zipEntry = new ZipEntry(zipEntryName);
try {
zipStream.putNextEntry(zipEntry);
zipStream.write(kmlFileContent.getBytes());
} catch (IOException e) {
logger.error("Error while zipping kml file content : " + e.getMessage());
}
finally {
try {
zipStream.closeEntry();
zipStream.close();
} catch (IOException e) {
logger.error("Error while closing zipped stream : " + e.getMessage());
}
}
I'm having problems with appending a generic object within an existing file. This method is supposed to append the object to the existing file if the parameters are "true" and overwrites the entire file if "false". The "false" statement works perfectly fine, it overwrites the entire file but I can't seem to get the append one to work. It seems to do nothing at first glance but when I placed a simple System.out.println("test"); in the while (true) loop, it runs forever. How can I fix this?
public <T> void writeOneObject(T type, boolean append) throws NotSerializableException{
if (append == true){
//TODO
if (file.exists ()){
ObjectOutputStream ois = null;
try{
ois = new ObjectOutputStream (new FileOutputStream (file, true));
while (true){
ois.writeObject(type);
}
}catch (StreamCorruptedException e){
}catch (EOFException e){
}catch (Exception e){
e.printStackTrace ();
}finally{
try{
if (ois != null) ois.close();
}catch (StreamCorruptedException e){
}catch (IOException e){
e.printStackTrace ();
}
}
}
}
else { //overwrites the entire file
try {
FileOutputStream fos = new FileOutputStream(file);
ObjectOutputStream oos = new ObjectOutputStream(fos);
oos.writeObject(type);
oos.flush();
oos.close();
} catch (FileNotFoundException ex) {
ex.printStackTrace();
} catch (StreamCorruptedException e) {
System.out.println("error");
} catch (IOException ex) {
ex.printStackTrace();
}
}
}
I also have this inside the class:
class NoHeaderObjectOutputStream extends ObjectOutputStream {
public NoHeaderObjectOutputStream(OutputStream os) throws IOException {
super(os);
}
protected void writeStreamHeader() {}
}
I have this method supposed to read a file:
/* Read file's content */
private ArrayList<String> readFromFile() {
File file = new File("jokesBody1.bjk");
ArrayList<String> list = new ArrayList<String>();
try {
file.createNewFile();
ObjectInputStream ois = new ObjectInputStream( new FileInputStream( file ) );
try {
list = (ArrayList)ois.readObject();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
ois.close();
} catch (IOException e) {
Log.e("log activity", "Can not read file: " + e.toString());
}
return list;
}
When I call it, it returns:
02-16 06:15:32.686: E/log activity(1380): Can not read file: java.io.IOException: open failed: EROFS (Read-only file system)
Even, if the file is read only, why I can't read it? I really can't understand what is wroong. I have this premission in my manifest:
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
Can someone give me a clue? I know that I'm missing something small, but I really can't spot it.
Here is how I write the file:
/* Write content to a file */
private void writeToFile(ArrayList<String> list, Context cont) {
File file = new File("jokesBody1.bjk");
FileOutputStream fos;
if(list != null){
try {
fos = cont.openFileOutput("jokesBody1.bjk", Context.MODE_PRIVATE);
ObjectOutputStream out = new ObjectOutputStream(fos);
out.writeObject(list);
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}else{
try {
file.createNewFile();
fos = openFileOutput("jokesBody1.bjk",Context.MODE_PRIVATE);
ObjectOutputStream out = new ObjectOutputStream(fos);
out.writeObject("");
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
You are trying to create the file, which of course fails on a read-only file.
Remove this line:
file.createNewFile();
This is usually used to create a new empty file before writing to it. You really don't need it if you just want to read a file that already exists.
EDIT:
Just use this:
ObjectInputStream ois = new ObjectInputStream( context.openFileInput("jokesBody1.bjk"));
Of course, you'll also have to pass a Context to the function.
You can only use File with a full path. For accessing your private files, use Context, just as you do when saving the file.
Your full function should look like:
private ArrayList<String> readFromFile(Context context) {
ArrayList<String> list = new ArrayList<String>();
try {
ObjectInputStream ois = new ObjectInputStream( context.openFileInput("jokesBody1.bjk"));
try {
list = (ArrayList)ois.readObject();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
ois.close();
} catch (IOException e) {
Log.e("log activity", "Can not read file: " + e.toString());
}
return list;
}
You aren't specifying any path:
File file = new File("jokesBody1.bjk");
So, you are not saying the app WHERE to look for the file.
Maybe, you want to search it here?
Environment.getExternalStorageDirectory()