Question

I’m trying to upload a file via URLConnection, but I need to read/write it as a binary file without any encoding changes.

So i’ve tried to read byte[] array from a FileInputStream, but now i have an issue. The PrintWriter object I use for outputing to the server does not allow me to do writer.write(content) (where content is of type byte[]). How can i fix this? Or is there another way to quickly copy binary data from a FileInputStream to a PrintWriter?

Thank you

Answer 1

Writer objects (including PrintWriter) are intended specifically for output of character data. It sounds like you want an OutputStream instead of a Writer here.

Where did your PrintWriter come from? If it was created by wrapping some kind of OutputStream with an OutputStreamWriter and then wrapping that with a PrintWriter, then you should just use the original write(byte[] b) method from the original OutputStream, rather than trying to use a Writer.

If you want to mix character output and byte output, you may need to use String.getBytes(). Check out this example:

OutputStream o = this.conn.getOutputStream(); // Based on your comment
String s = "Hello, world!";
byte[] b = ...;      // These are the raw bytes that you want to write
o.write(s.getBytes("UTF-8"));
o.write(b);

(Of course, this will only work if the system that is reading your output understands that you are writing a mixture of characters and raw bytes and knows how to handle the mixed data that you are sending it.)