How do you read from an InputStream in Java and convert to byte array?

Question

I am currently trying to read in data from a server response. I am using a Socket to connect to a server, creating a http GET request, then am using a Buffered Reader to read in data. Here is what the code looks like compacted:

    Socket conn = new Socket(server, 80);
    //Request made here
    BufferedReader inFromServer = new BufferedReader(new InputStreamReader(conn.getInputStream()));
    String response;
    while((response = inFromServer.readLine()) != null){
        System.out.println(response);
    }

I would like to read in the data, instead of as a String, as a byte array, and write it to a file. How is this possible? Any help is greatly appreciated, thank you.

possible duplicate of BufferedReader directly to byte[]

Elliott Frisch
– Elliott Frisch

2014-04-28 05:59:30 +00:00
Commented Apr 28, 2014 at 5:59 — Elliott Frisch
– Elliott Frisch, Commented Apr 28, 2014 at 5:59

AdityaKeyal · Accepted Answer · 2014-04-28 06:00:31Z

4

You need to use a ByteArrayOutputStream, do something like the below code:

Socket conn = new Socket(server, 80);
        //Request made here
        InputStream is = conn.getInputStream();

        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int readBytes = -1;

        while((readBytes = is.read(buffer)) > 1){
            baos.write(buffer,0,readBytes);
        }

        byte[] responseArray = baos.toByteArray();

answered Apr 28, 2014 at 6:00

AdityaKeyal

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6 Comments

user3579421 Over a year ago

Thank you very much. This is very helpful. I have just one more questions however. So the way the HTTP response is formatted, is first comes the header then the file contents. So in order to make a byte array of the proper size I'd have to first parse the header and get the info, and then read the file. How would you recommend doing this?

AdityaKeyal Over a year ago

Given your issue ill recommend a slightly different approach, 1st read the response as a text (2 parts) header and content. The convert the content of text into byte array using getBytes()

user3579421 Over a year ago

I did consider that. Would there be a difference in the time it would take to read it as a text rather than as bytes? Because my whole intention here is to calculate download speed, and whoever's code I've looked at has downloaded the file as bytes.

AdityaKeyal Over a year ago

There would be a slight difference in time couple of ms. So if you are looking at that kind of precision then you might want to use a byte reading (into the ByteArrayOutputStream) and check the byte array for when the content start (either by converting the same into a string or by checking for the byte code equivalent of Content-Length etc) .

user3579421 Over a year ago

Do you think there is anyway I can read the file as text up until the end of the header, then continue reading as bytes? Maybe there is someway I can change the position of the InputStream so that it starts where the BufferedReader left off?

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Suren Raju · Accepted Answer · 2014-04-28 05:57:41Z

1

One way is to use Apache commons-io IOUtils

byte[] bytes = IOUtils.toByteArray(inputstream);

answered Apr 28, 2014 at 5:57

Suren Raju

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Comments

morgano · Accepted Answer · 2014-04-28 05:58:29Z

1

With plain java:

    ByteArrayOutputStream output = new ByteArrayOutputStream();

    try(InputStream stream = new FileInputStream("myFile")) {
        byte[] buffer = new byte[2048];
        int numRead;
        while((numRead = stream.read(buffer)) != -1) {
            output.write(buffer, 0, numRead);
        }
    } catch(IOException e) {
        e.printStackTrace();
    }

    // and here your bytes
    byte[] myDesiredBytes = output.toByteArray();

answered Apr 28, 2014 at 5:58

morgano

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Comments

Niraj Patel · Accepted Answer · 2014-04-28 05:59:26Z

1

If you are not using Apache commons-io library in your project,I have pretty simple method to do the same without using it..

   /*
     * Read bytes from inputStream and writes to OutputStream,
     * later converts OutputStream to byte array in Java.
     */
    public static byte[] toByteArrayUsingJava(InputStream is)
    throws IOException{
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        int reads = is.read();

        while(reads != -1){
            baos.write(reads);
            reads = is.read();
        }

        return baos.toByteArray();

    }

answered Apr 28, 2014 at 5:59

Niraj Patel

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