Develop Reference

Stream file from URL to File without storing it in the memory

I want to download a file from a URL and store it into the file system. However I have memory limitation and I don't want to store it in the memory before. I am not a java expert and I am a bit lost with all the class InputStream, BufferedReader, FileOutputStream, etc. Could you help me please ?
For now I have:
URLConnection ucon = url.openConnection();
ucon.connect();
InputStream is = ucon.getInputStream();
// Create a reader for the input stream.
BufferedReader br = new BufferedReader(isr);
// ?
FileOutputStream fos = context.openFileOutput(FILENAME, Context.MODE_PRIVATE);
// Here the content can be too big for the memory...
fos.write(content.getBytes());
fos.close();
Please, could you give me some clue ? I was thinking also to read it chunk by chunk, but I am not sure what would be the easiest with java...

you can use apache commons
org.apache.commons.io.FileUtils.copyURLToFile(URL, File)
I guess it may not work on android
I use this code
InputStream input = connection.getInputStream();
byte[] buffer = new byte[4096];
int cnt = - 1;
OutputStream output = new FileOutputStream(file);
while ( (cnt = input.read(buffer)) != -1)
{
output.write(buffer, 0, cnt);
}
output.close();

Java servlet and IO: Create a file without saving to disk and sending it to the user

I`m hoping can help me out with a file creation/response question.
I know how to create and save a file. I know how to send that file back to the user via a ServletOutputStream.
But what I need is to create a file, without saving it on the disk, and then send that file via the ServletOutputStream.
The code above explains the parts that I have. Any help appreciated. Thanks in Advance.
// This Creates a file
//
String text = "These days run away like horses over the hill";
File file = new File("MyFile.txt");
Writer writer = new BufferedWriter(new FileWriter(file));
writer.write(text);
writer.close();
// Missing link goes here
//
// This sends file to browser
//
InputStream inputStream = null;
inputStream = new FileInputStream("C:\\MyFile.txt");
byte[] buffer = new byte[8192];
ByteArrayOutputStream baos = new ByteArrayOutputStream();
int bytesRead;
while ( (bytesRead = inputStream.read(buffer)) != -1)
baos.write(buffer, 0, bytesRead);
response.setContentType("text/html");
response.addHeader("Content-Disposition", "attachment; filename=Invoice.txt");
byte[] outBuf = baos.toByteArray();
stream = response.getOutputStream();
stream.write(outBuf);

You don't need to save off a file, just use a ByteArray stream, try something like this:
inputStream = new ByteArrayInputStream(text.getBytes());
Or, even simpler, just do:
stream.write(text.getBytes());
As cHao suggests, use text.getBytes("UTF-8") or something similar to specify a charset other than the system default. The list of available charsets is available in the API docs for Charset.

How to write file data correctly?

My application is unable to transfer data properly over a socket connection and write it to a file properly. Files over about 65,535 bytes get corrupted and are no longer recognized by the programs designed to run them.
I have been able to send small .doc and .txt files successfully, but .mp3 .wmv .m4a .avi and just about anything else does not work. Neither do larger docs.
I have looked all over the internet for a solution to this problem. I have repeatedly tweaked the I/O code to fix the problem but it still doesn't work! Here is the I/O code in the super class that handles sending and receiving files. If you need anymore information/other parts of code, let me know.
protected void sendFile() throws IOException {
byte[] bytes = new byte[(int) file.length()];
buffin = new BufferedInputStream(new FileInputStream(file));
int bytesRead = buffin.read(bytes,0,bytes.length);
System.out.println(bytesRead);
out = sock.getOutputStream();
out.write(bytes,0,fileBytes);
out.flush();
out.close();
}
protected void receiveFile() throws IOException {
byte[] bytes = new byte[fileBytes];
in = sock.getInputStream();
for(int i=0;i<fileBytes;i++) {
in.read(bytes);
}
fos = new FileOutputStream("/Datawire/"+fileName);
buffout = new BufferedOutputStream(fos);
buffout.write(bytes,0,fileBytes);
buffout.flush();
buffout.close();
}
UPDATED CODE (that works):
protected void sendFile() throws IOException {
if((file.length())<63000) {
byte[] bytes = new byte[(int)file.length()];
buffin = new BufferedInputStream(new FileInputStream(file));
buffin.read(bytes,0,bytes.length);
out = sock.getOutputStream();
out.write(bytes,0,bytes.length);
out.close();
} else {
byte[] bytes = new byte[32000];
buffin = new BufferedInputStream(new FileInputStream(file));
out = sock.getOutputStream();
int bytesRead;
while((bytesRead = buffin.read(bytes))>0) {
out.write(bytes,0,bytesRead);
}
out.close();
}
}
protected void receiveFile() throws IOException {
if(fileBytes<63000) {
byte[] bytes = new byte[32000];
in = sock.getInputStream();
System.out.println(in.available());
in.read(bytes,0,fileBytes);
fos = new FileOutputStream("/Datawire/"+fileName);
buffout = new BufferedOutputStream(fos);
buffout.write(bytes,0,bytes.length);
buffout.close();
} else {
byte[] bytes = new byte[16000];
in = sock.getInputStream();
fos = new FileOutputStream("/Datawire/"+fileName);
buffout = new BufferedOutputStream(fos);
int bytesRead;
while((bytesRead = in.read(bytes))>0) {
buffout.write(bytes,0,bytesRead);
}
buffout.close();
}
}

The issue is that you are sending only chunks of it. That is, you are only sending 64k of the file ever. If the file is ever larger then 64k the other end will never see it.
You want to continously read from the BufferedInputStream until the read() returns either less then the length or -1.

Your code is completely wrong. This is how to copy a stream in Java:
int count;
byte[] buffer = new byte[8192]; // more if you like but no need for it to be the entire file size
while ((count = in.read(buffer)) > 0)
{
out.write(buffer, 0, count);
}
You should use this both when sending the file and when receiving the file. At present your sending method hopes that the entire file fits into memory; fits into INTEGER_MAX bytes; and is read in one chunk by the read method, without even checking the result. You can't assume any of those things. Your receive method is complete rubbish: it just keeps overwriting the same array, again without checking any read() results.
EDIT: Your revised code is just as bad, or worse. You are calling read() to check for EOS and then throwing that byte away, and then calling read() again and throwing away the read count it returns. You pointlessly have a different path for files < 64000, or 63000, or whatever it is, that has zero benefit except to give you two code paths to test, or possibly four, instead of one. The network only gives you 1460 bytes at a time at best anyway so what is the point? You already have (a) a BufferedInputStream with a default buffersize of 8192, and (b) my code that uses a byte[] buffer of any size you like. My code above works for any amount of data in two lines of executable code. Yours is 20. QED.

I suggest that you use some good library to read and write file contents as well as socket read/write. For example Apache Commons IO. If you insist on writig code yourself, do it smaller chunks rather than the whole file at once.

You have to consider that InputStream.read returns the number of bytes read which may be less than the total number of bytes in the file.
You would probably be better off just letting something like CopyUtils.copy take care of this for you.

You need to loop until bytesRead < 0. You need to make sure that fileBytes is => than the transferred file.
protected void receiveFile() throws IOException {
byte [] bytes = new byte [fileBytes];
InputStream is = sock.getInputStream();
FileOutputStream fos = new FileOutputStream("/Datawire/"+fileName);
BufferedOutputStream bos = new BufferedOutputStream(fos);
int bytesRead = is.read(bytes,0,bytes.length);
int current = bytesRead;
do {
bytesRead =
is.read(bytes, current, (bytes.length-current));
if(bytesRead >= 0) current += bytesRead;
} while(bytesRead > -1);
bos.write(bytes, 0 , current);
bos.flush();
bos.close();
}

Android copying large inputstream to file very slow

I have an app that is downloading a zip file and then copying this file to a temporary file on the sd card on the phone, but it is being very very slow.
InputStream in = new BufferedInputStream(url.openStream(), 1024);
File tempFile = File.createTempFile("arc", ".zip", targetDir); //target dir is a file
String tempFilePath = tempFile.getAbsolutePath();
OutputStream out = new BufferedOutputStream(new FileOutputStream(tempFile));
//copying file (in different void)
byte[] buffer = new byte[8192];
int len;
len = in.read(buffer);
enter code here
//it loops here for AGES
while (len >= 0) {
out.write(buffer, 0, len);
len = in.read(buffer);
}
in.close();
out.close();
My file is about 20MB, initially I had the buffer size of 1024, and changed it to 8192 thinking it may speed it up but it seemed to make no difference? I always finishes, and I get no errors it just takes ages!
I have searched to try and find a solution but I'm not coming up with anything so I may be going about this totally the wrong way?
Can anyone see what I'm doing wrong?
Bex

Donot increase buffer size. That may cause your application MemoryOutOfBoundsException.
There are varous factors for which your download will be slow. Weak internet connection, Weak file transfer and receiveing mode is also responsible. It also depend on capacity of device. Check whether you are using following code to create inputstream
URL u = new URL("enter url url here");
HttpURLConnection c = (HttpURLConnection) u.openConnection();
c.setRequestMethod("GET");
c.setDoOutput(true);
c.connect();
InputStream in = c.getInputStream();
Thanks
Deepak

URL Connection (FTP) in Java - Simple Question

I have a simple question. I'm trying to upload a file to my ftp server in Java.
I have a file on my computer, and I want to make a copy of that file and upload it. I tried manually writing each byte of the file to the output stream, but that doesn't work for complicated files, like zip files or pdf files.
File file = some file on my computer;
String name = file.getName();
URL url = new URL("ftp://user:password#domain.com/" + name +";type=i");
URLConnection urlc = url.openConnection();
OutputStream os = urlc.getOutputStream();
//then what do I do?
Just for kicks, here is what I tried to do:
OutputStream os = urlc.getOutputStream();
BufferedReader br = new BufferedReader(new FileReader(file));
String line = br.readLine();
while(line != null && (!line.equals(""))) {
os.write(line.getBytes());
os.write("\n".getBytes());
line = br.readLine();
}
os.close();
For example, when I do this with a pdf and then try and open the pdf that I run with this program, it says an error occurred when trying to open the pdf. I'm guessing because I am writing a "\n" to the file? How do I copy the file without doing this?

Do not use any of the Reader or Writer classes when you're trying to copy the byte-for-byte exact contents of a binary file. Use these only for plain text! Instead, use the InputStream and OutputStream classes; they do not interpret the data at all, while the Reader and Writer classes interpret the data as characters. For example
OutputStream os = urlc.getOutputStream();
FileInputStreamReader fis = new FileInputStream(file);
byte[] buffer = new byte[1000];
int count = 0;
while((count = fis.read(buffer)) > 0) {
os.write(buffer, 0, count);
}
Whether your URLConnection usage is correct here, I don't know; using Apache Commons FTP (as suggested elsewhere) would be an excellent idea. Regardless, this would be the way to read the file.

Use a BufferedInputStream to read and BufferedOutputStream to write. Take a look at this post: http://www.ajaxapp.com/2009/02/21/a-simple-java-ftp-connection-file-download-and-upload/
InputStream is = new FileInputStream(localfilename);
BufferedInputStream bis = new BufferedInputStream(is);
OutputStream os =m_client.getOutputStream();
BufferedOutputStream bos = new BufferedOutputStream(os);
byte[] buffer = new byte[1024];
int readCount;
while( (readCount = bis.read(buffer)) > 0) {
bos.write(buffer, 0, readCount);
}
bos.close();

FTP usually opens another connection for data transfer.
So I am not convinced that this approach with URLConnection is going
to work.
I highly recommend that you use specialized ftp client. Apache commons
may have one.
Check this out
http://commons.apache.org/net/api/org/apache/commons/net/ftp/FTPClient.html