How to read byte[] of variable size from DataInputStream in Java?

Question

I'm working on a TCP server project and I need to transfer a file via a byte[] using a DataOutputStream and a DataInputStream and I've gotten stuck. I'm able to write the byte array to the output stream with no problems, but I was looking at the documentation for the DataInputStream and the method that it seems I would want is read(byte[] b). The issue is that this requires I create a byte[] beforehand, but I don't necessarily know what the size it needs to be so I need some help on how I should go about doing this.

You don't care. Just use the standard copy loop with a byte array of 8192 or whatever you like. — user207421, Feb 10 '17 at 20:31
Send the size first, then on the receiver, read the size and build the array — David Zimmerman, Feb 10 '17 at 20:47

score 1 · Answer 1 · edited May 23 '17 at 12:33

1

Take a look at Apache Commons IO library. It has a utility class called IOUtils which can read an entire input stream into byte array without you having to declare a byte [] beforehand. For more information look at this

edited May 23 '17 at 12:33

Community

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answered Feb 10 '17 at 21:45

opensam

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score 0 · Answer 2 · answered Feb 12 '17 at 01:07

0

You don't. All you need is the standard Java copy loop:

byte[] buffer = new byte[8192]; // or wherever you like > 0
int count;
while ((count = in.read(buffer)) > 0)
{
    out.write(buffer, 0, count);
}

answered Feb 12 '17 at 01:07

user207421

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score -1 · Answer 3 · answered Feb 11 '17 at 19:05

-1

I made a library for TCP server and client. You might as well use it. GitHub

It is not much, but it is simple.

answered Feb 11 '17 at 19:05

mihibo5

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How to read byte[] of variable size from DataInputStream in Java?

3 Answers3