How to send files along with parameters over http

Question

I am trying to send a zipfile from my android application to our server and I keep getting a 411 length required error.

Here is the code that I am using to do that.

    HttpPost post = new HttpPost("http://www.xyz.org/upload.json");
    post.setHeader(C.constants.HTTP_CONTENT_TYPE, "application/octet-stream");

    try {
        FileInputStream fis = new FileInputStream("/data/data/org.myapp.appname/app_content.zip");

        InputStreamEntity reqEntity = new InputStreamEntity(fis, -1);
        post.setEntity(reqEntity);
        String response = doPost(post);

        Log.v(tag, "response from server " + response);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }

What am I doing wrong here and may I also know how I can add more parameters with this post to send them to the server.

Answer 1

You should use a multipart MIME type, and parts for each parameters and for the files. See this old blog post of mine.

As you should know, an HTTP request (and response, too) is made up of two section: a header and a body (also called entity). In the header you specify a Content-Type so that the server script knows how to interpret the following bytes (you can also specify the encoding for textual data on the same line).

After the header, the client sends an empty line and an optional entity. A multipart entity is like a stack of parts separated by a boundary. This is what your desired HTTP request should look like on the wire:

POST /path/to/script.json HTTP/1.1
Host: localhost
Content-Type: multipart/form-data; boundary=a2ksdf0?--

a2ksdf0?--
Content-Disposition: form-data; name="profile_picture"; filename="me.png"
Content-Type: image/png

<content here>
a2ksdf0?--
Content-Disposition: form-data; name="username";
Content-Type: text/plain

Joe Black

BTW, it's the first time I see an upload script named upload.json. What do you use on the server side?