Android - Write byte array to OutputStreamWriter

Question

I have an application that uploads photos through a web service. In the past, I loaded a file into a stream, and converted to Base64. Then I posted the resulting string through the write() method of an OutputStreamWriter. Now, the web service has changed, and it expects multipart/form-data and it does not expect Base64.

So somehow I need to post the chararters of this file as is without conversion. I'm sure I'm close, but all I ever get is a content lengh underflow or overflow. The odd thing is that in the debugger I can see that my buffer length is the same length as the string I'm posting. Here's what I'm doing and hopefully enough code:

// conn is my connection
OutputStreamWriter dataStream = new OutputStreamWriter(conn.getOutputStream());

// c is my file
int bytesRead = 0;
long bytesAvailable = c.length();

while (bytesAvailable > 0) {
   byte[] buffer = new byte[Math.min(12288, (int)bytesAvailable)];
   bytesRead = fileInputStream.read(buffer, 0, Math.min(12288, (int)bytesAvailable));

   // assign the string if needed.
   if (bytesRead > 0) {
      bytesAvailable = fileInputStream.available();

      // I've tried many encoding types here.
      String sTmp = new String(buffer, "ISO-8859-1");
      // HERE'S the issue.  I can't just write the buffer,
      dataStream.write(sTmp);
      dataStream.flush();
// Yes there's more code, but this should be enough to show why I don't know what I'm doing!

Is there any reason why you convert the bytes to strings instead of writing them raw into the output stream? — Michael
– Michael, Commented Jul 18, 2012 at 14:07
Because the write() method of OutputStreamWriter accepts char[] or string. Not byte[]. — Paul
– Paul, Commented Jul 18, 2012 at 14:14

AAnkit · Accepted Answer · 2016-08-03 18:18:27Z

17

change

OutputStreamWriter dataStream = new OutputStreamWriter(conn.getOutputStream());

with this

DataOutputStream dataStream = new DataOutputStream(conn.getOutputStream());

and directly call dataStream.write(buffer);

let me know how it behave

Edit: edited answer according to comment

edited Aug 3, 2016 at 18:18

answered Jul 18, 2012 at 14:24

AAnkit

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3 Comments

Paul Over a year ago

'conn' is an HttpURLConnection. getOutputStream() does not return a 'DataOutputStream', nor can it be casted.

Paul Over a year ago

Ugh sorry. Need coffee. DataOutputStream dataStream = new DataOutputStream(conn.getOutputStream());

davenpcj Over a year ago

Be cautious with this. Although it will allow you to write a byte[] to the output, the other methods of DataOutputStream are not compatible with OutputStremWriter. In particular, OutputStreamWriter can be given a standard encoding for writing Strings, where DataOutputStream has it's own proprietary encodings.

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