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Byte array to file in java without overwriting,

The code below gets a byte array from an HTTP request and saves it in bytes[], the final data will be saved in message[].
I check to see if it contains a header by converting it to a String[], if I do, I read some information from the header then cut it off by saving the bytes after the header to message[].
I then try to output message[] to file using FileOutputStream and it works slightly, but only saves 10KB of information,one iteration of the while loop, (seems to be overwriting), and if I set the FileOutputStream(file, true) to append the information, it works... once, then the file is just added on to the next time I run it, which isn't what I want. How do I write to the same file with multiple chunks of bytes through each iteration, but still overwrite the file in completeness if I run the program again?
byte bytes[] = new byte[(10*1024)];
while (dis.read(bytes) > 0)
{
//Set all the bytes to the message
byte message[] = bytes;
String string = new String(bytes, "UTF-8");
//Does bytes contain header?
if (string.contains("\r\n\r\n")){
String theByteString[] = string.split("\r\n\r\n");
String theHeader = theByteString[0];
String[] lmTemp = theHeader.split("Last-Modified: ");
String[] lm = lmTemp[1].split("\r\n");
String lastModified = lm[0];
//Cut off the header and save the rest of the data after it
message = theByteString[1].getBytes("UTF-8");
//cache
hm.put(url, lastModified);
}
//Output message[] to file.
File f = new File(hostName + path);
f.getParentFile().mkdirs();
f.createNewFile();
try (FileOutputStream fos = new FileOutputStream(f)) {
fos.write(message);
} catch (IOException ioe) {
ioe.printStackTrace();
}
}
}

You're opening a new FileOutputStream on each iteration of the loop. Don't do that. Open it outside the loop, then loop and write as you are doing, then close at the end of the loop. (If you use a try-with-resources statement with your while loop inside it, that'll be fine.)
That's only part of the problem though - you're also doing everything else on each iteration of the loop, including checking for headers. That's going to be a real problem if the byte array you read contains part of the set of headers, or indeed part of the header separator.
Additionally, as noted by EJP, you're ignoring the return value of read apart from using it to tell whether or not you're done. You should always use the return value of read to know how much of the byte array is actually usable data.
Fundamentally, you either need to read the whole response into a byte array to start with - which is easy to do, but potentially inefficient in memory - or accept the fact that you're dealing with a stream, and write more complex code to detect the end of the headers.
Better though, IMO, would be to use an HTTP library which already understands all this header processing, so that you don't need to do it yourself. Unless you're writing a low-level HTTP library yourself, you shouldn't be dealing with low-level HTTP details, you should rely on a good library.

Open the file ahead of the loop.
NB you need to store the result of read() in a variable, and pass that variable to new String() as the length. Otherwise you are converting junk in the buffer beyond what was actually read.

There is an issue with reading the data - you read only part of the response (because at that moment not all data was transfered to you yet) - so obviusly you write only that part.
check this answer for how to read full data from the InputStream:
Convert InputStream to byte array in Java

How to Write Image File from Request Body Without Writing to Memory Nodejs

I'm trying to (HTTP) POST an image to a Nodejs server that is configured using Express. I have been able to accomplish this successfully using JSON, but unless I am mistaken, there is no way to obtain the image string without loading the entire request body into a new variable before parsing it as JSON. Since images are quite large and the image should already be stored in the request body anyway, is there a way to immediately pipe the image contents into fs.writeFile()? The content type for the request does not have to be JSON. I have tried using a querystring as well, but that was unsuccessful. The content type cannot be just an image though because I have to include a tag for the image too (in this case the user's email address).
Here is the code for when I attempted to use a query string. It is located in a post route method for the express app:
fs.writeFile('profiles/images/user.png', new Buffer(req.body.image, 'base64'),
function(error)
{
if (error)
res.end(error);
}
);
No error occurs, and the code creates the .png file, but the file is somehow corrupted and is larger than it should be.
All of this is actually for an Android app, so here is also the Java code that I am using to send the request:
URLConnection connection = new URL(UPLOAD_PICTURE_URL).openConnection();
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded;");
connection.setDoOutput(true);
String image = Base64.encodeToString(
IOUtils.toByteArray(new FileInputStream(filePath)),
Base64.NO_WRAP
);
OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream());
out.write("email=" + email + "&image=" + image);
out.close();
Perhaps this belongs in another topic, but along the same lines, does anybody know a way to pipe the file input stream in the android code directly to the URLConnection's output stream with base64 encoding? I have tried writing the string literal (the out.write() line above ^) and then creating a Base64OutputStream to write the image before piping that stream into the URLConnection's outputstream, but calling req.body.image in the node app after doing that just returns undefined. And finally, does anybody know if IOUtils.toByteArray() (from Apache Commons), when used as the input argument for an input/output stream constructor, writes the entire byte array to memory anyway on the Android side? If so, is there a way of avoiding that too?
Thanks in advance.

Get File Length from header Java Android

I have Java code I tried many variants but didn't help.
Some hosting are closing file Content length (size of file )so please help me to read file size from header.
Here is the part of my streaming code when so I need to open the list and read the int value am I right?
is = ucon.getInputStream();
fileLength = ucon.getContentLength();
List headersize = ucon.getHeaderFields().get("content-Lenght");

You could do something like this:
URL url = new URL("https://www.google.com/logos/classicplus.png");
URLConnection openConnection = url.openConnection();
System.out.println(openConnection.getContentLength());
According documentation:
public int getContentLength()
Returns the value of the content-length header field.
Returns: the content length of the resource that this connection's URL references, or -1 if the content length is not known.
The method does the same thing you are trying to do manually. And if not defined you will receive -1

You have spelt Content-Length wrong. Use this spelling

Specify Content-Length while serving a file from the database

In a servlet, I want to read an EML from my database and serving it to the client with a "download file" UI. When I specify the Content-Length header, the download takes minutes to start. When I don't, everything works well, but I do want to set that header :) What am I missing?
// part is javax.mail.Part
response.setHeader("Content-Disposition", "attachment" + filename);
response.setContentType(mime);
response.setContentLength(part.getSize()); // This line causes the problem
IOUtils.copy(part.getInputStream(), out);

Just a guess - maybe the file has to be fetched from DB to get its size ? Save the size to separate column and serve the value from there. Also working with the file-in-DB through java.sql.Blob should work.
Unfortunately in your sample there is no info where you take the part object from.

Issue encoding java->xls

This is not a pure java question and can also be related to HTML
I've written a java servlet that queries a database table and shows the
result as a html table. The user can also ask to receive the result as
an Excel sheet.
Im creating the Excel sheet by printing the same html table, but with
the content-type of "application/vnd.ms-excel". The Excel file is
created fine.
The problem is that the tables may contain non-english data so I want
to use a UTF-8 encoding.
PrintWriter out = response.getWriter();
response.setContentType("application/vnd.ms-excel:ISO-8859-1");
//response.setContentType("application/vnd.ms-excel:UTF-8");
response.setHeader("cache-control", "no-cache");
response.setHeader("Content-Disposition", "attachment; filename=file.xls");
out.print(src);
out.flush();
The non-english characters appear as garbage (áéíóú)
Also I tried converting to bytes from String
byte[] arrByte = src.getBytes("ISO-8859-1");
String result = new String(arrByte, "UTF-8");
But I Still getting garbage, What can I do?.
Thanks
UPDATE: if I open the excel file in notepad + + the type of file encoding is "UTF-8 without BOM", if I change the encoding to "UTF-8" and then open the file in Excel, the characters "áéíóú" look good.

Excel is a binary format, not a text format, so you should not need to set any encoding, since it simply doesn't apply. Whatever system you are using to build the excel file (e.g. Apache Poi) will take care of the encoding of text within the excel file.
You should not try to convert the recieved bytes to a string, just store them in a byte array or write them out to a file.
EDIT: from the comment, it doesn't sound as if you are using a "real" binary excel file, but a tab delimited text file (CSV). In that case, make sure you use consistent encoding, e.g UTF-8 throughout.
Also, before calling response.getWriter(), call setContentType first.
See HttpServletResponse.getPrintWriter()
EDIT: You can try writing the BOM. It's normally not required, but file format handling in Office is far from normal...
Java doesn't really have support for the BOM. You'll have to fake it. It means that you need to use the response outputStream rather than writer, since you need to write raw bytes (the BOM). So you change your code to this:
response.setContentType("application/vnd.ms-excel:UTF-8");
// set other headers also, "cache-control" etc..
OutputStream outputStream = response.getOutputStream();
outputStream.write(0xEF); // 1st byte of BOM
outputStream.write(0xBB);
outputStream.write(0xBF); // last byte of BOM
// now get a PrintWriter to stream the chars.
PrintWriter out = new PrintWriter(new OutputStreamWriter(outputStream,"UTF-8"));
out.print(src);

Do you get "garbage" when you print result to standard output?
Edit (code in code tags from the comment below):
response.setContentType("application/vnd.ms-excel; charset=UTF-8")

Try using the ServletResponse.setCharacterEncoding(java.lang.String charset) method.
response.setCharacterEncoding("UTF-8");

I had the same issue.. i fixed it with using print() instead of write()
outputStream.print('\ufeff');