Java - Upload OutputStream as HTTP File Upload

Question

I've got a legacy application that writes to an OutputStream, and I'd like to have the contents of this stream uploaded as a file to a Servlet. I've tested the Servlet, which uses commons-fileupload, using JMeter and it works just fine.

I would use Apache HttpClient, but it requires a File rather than just an output stream. I can't write a file locally; if there was some in-memory implementation of File perhaps that might work?

I've tried using HttpURLConnection (below) but the server responds with "MalformedStreamException: Stream ended unexpectedly".

        URL url = new URL("http", "localhost", 8080, "/upload");
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.setDoOutput(true);
        String boundary = "---------------------------7d226f700d0";
        connection.setRequestProperty("Content-Disposition", "form-data; name=\"file\""); 
        connection.setRequestProperty("Content-Type", "multipart/form-data; boundary="+boundary);
        connection.setRequestProperty("Accept", "application/json");
        connection.setRequestMethod("POST");   
        connection.setChunkedStreamingMode(0);
        connection.connect();           

        OutputStream out = connection.getOutputStream();
        byte[] boundaryBytes =("--" + boundary + "\r\n").getBytes();
        out.write(boundaryBytes);


        //App writes to outputstream here

        out.write("\r\n".getBytes());
        out.write(("--"+boundary+"--").getBytes());
        out.write("\r\n".getBytes());

        out.flush();
        out.close();
        connection.disconnect();

By definition, there is no in-memory implementation of File. You can, however, replicate the HttpClient method and pass your bytes or stream directly, as that API most likely loads the file's bytes via a stream. — FThompson
– FThompson, Commented Sep 27, 2012 at 14:24

jtahlborn · Accepted Answer · 2012-09-27 14:38:35Z

1

The PostMethod allows you to set a RequestEntity, which is an interface which you can implement. you just need to implement the RequestEntity.writeRequest method appropriately.

Or, if you want HttpClient to handle the multi-part stuff for you, you could use MultipartRequestEntity with a custom Part.

answered Sep 27, 2012 at 14:38

jtahlborn

53.8k5 gold badges80 silver badges122 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

DeejUK Over a year ago

Excellent - looks like I could even just implement PartSource. The legacy app takes OutputStream as an argument, and then writes to it, so I'm in control of what OutputStream goes in there. I'm guessing I could use a ByteArrayOutputStream, have the legacy code write to that, generate the byte array, and then implement a PartSource that takes a byte array instead of a file, and then provides an ByteArrayInputStream from that?

jtahlborn Over a year ago

@Deejay - you could do that, but it wouldn't scale very well if you have large streams.

Collectives™ on Stack Overflow

Java - Upload OutputStream as HTTP File Upload

1 Answer 1

2 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related