Http Connection stream only sends 2048 bytes

[Alex Parvan]

Hi, i'm having some trouble sending a byte array via http connection stream to servlet, here is my client code:

byte[] bytes = ImageByteArray.getByteArrayFromImage(img);
System.out.println(bytes.length); // this prints 167096
http = (HttpConnection) Connector.open("http://localhost:8080/Servlet/ImageServlet");
http.setRequestProperty("Content-Type", "multipart/form-data"); // i also tried image/jpg here
http.setRequestMethod(HttpConnection.POST);
os = http.openOutputStream();
os.write(bytes);

and the servlet code:

        ServletInputStream in = request.getInputStream();
        byte[] data = null;
        int chunkSize = 512;
        int index = 0;
        int readLength = 0;
        data = new byte[chunkSize];
        do {
            if (data.length < index + chunkSize) {
                byte[] newData = new byte[index + chunkSize];
                System.arraycopy(data, 0, newData, 0, data.length);
                data = newData;
            }
            readLength = in.read(data, index, chunkSize);
            index += readLength;
            System.out.println(data.length);
        } while (readLength == chunkSize);
        saveImageToDisk(data);

The servlet reads 4 chunks (2048 bytes) and then stops, and ofcourse the image cannot be read, i get an EOFException. I tried forcing the servlet to read byte[167096] (167096 is bytes.length on the client) and the image gets created but only the first ~3% of the pixels are shown, the rest is just white.

Maybe someone can tell me what i'm doing wrong ? i would appreciate it.
Thanks,
Alex

[Rob Spoor]

I suggest you take a look at ByteArrayOutputStream. It will make the problem as easy as simple InputStream-to-OutputStream copying after which you call toByteArray() on the ByteArrayOutputStream to get the byte array.

However, in your case I see that you are first gathering all data in a byte[], then save that byte[] to disk. Why not use a direct FileOutputStream to copy the contents of the InputStream to instead of saving the intermediate result?

[Alex Parvan]

Rob Prime wrote:I suggest you take a look at ByteArrayOutputStream. It will make the problem as easy as simple InputStream-to-OutputStream copying after which you call toByteArray() on the ByteArrayOutputStream to get the byte array.

I don't really understand what do you mean by this, isn't my code working the way it is ?

Rob Prime wrote:However, in your case I see that you are first gathering all data in a byte[], then save that byte[] to disk. Why not use a direct FileOutputStream to copy the contents of the InputStream to instead of saving the intermediate result?

I'm not really interested in saving a file to disk, i just did that so i can check if the image came out ok.

[Alex Parvan]

I was never good at using streams, i always skipped them, the error occured because i didn't read the stream correctly.

It's working, and the complete code is:
J2ME client code:

byte[] bytes = ImageByteArray.getByteArrayFromImage(img);
            http = (HttpConnection) Connector.open("http://localhost:8080/Servlet/ImageServlet", Connector.READ_WRITE, false); //not sure what READ_WRITE and false does :)
            http.setRequestMethod(HttpConnection.POST);
            http.setRequestProperty("Connection", "keep-alive"); //not sure what this does either =)
            http.setRequestProperty("Content-Type", "multipart/form-data");
            http.setRequestProperty("Content-Length", bytes.length + "");

            os = http.openOutputStream();
            os.write(bytes);

Servlet code:

        ServletInputStream in = request.getInputStream();
        byte[] data = new byte[0];
        byte[] buffer = new byte[512];
        int bytesRead;
        while ( (bytesRead = in.read(buffer)) > 0 ) {
            byte[] newData = new byte[data.length + bytesRead];
            System.arraycopy(data, 0, newData, 0, data.length);
            System.arraycopy(buffer, 0, newData, data.length, bytesRead);
            data = newData;
        }
        useBytesToDoSomethingWithThem(data);

[Rob Spoor]

That should work if you change the "> 0" on line 6 of the servlet code to ">= 0". If read returns 0 that does not mean there is no more data, only that there is no data right now. A return value of -1 is used to indicate there is no data and there won't be any data anymore.