How to post image data from j2me to ASP.net MVC 3? - asp.net-mvc-3

Question

I'm making a j2me mobile application which can post images (as byte[]) and other simple data (strings, ints, floats, etc) on a ASP.net MVC 3 website. Currently the application and website are nearly done, except the part where the app can post the image data on the website.
Here is the datamodel I'd like to post to the website (j2me):
public class DataModel {
private String description = null;
private float latitude = 0;
private float longitude = 0;
private long timestamp = 0;
private String userName = null;
private byte[] imageData = null;
private String contentType = null;
// getters and setters...
}
This is the model my website expects (ASP.net MVC3 C#):
public class Model
{
public string Description { get; set; }
public float Latitude { get; set; }
public float Longitude { get; set; }
public long Timestamp { get; set; }
public string UserName { get; set; }
public byte[] Image { get; set; }
}
This is the (simplified) code I use to send the data (j2me):
InputStream in = null;
OutputStream out = null;
// url contains all the simple data
String encodedUrl = UrlEncoder.encodeUrl(url);
this.connection = (HttpConnection)Connector.open(encodedUrl);
byte[] imageData = DataModel.getImageData();
this.connection.setRequestMethod(HttpConnection.POST);
this.connection.setRequestProperty("Content-Length", imageData.length + "");
out = this.connection.openOutputStream();
out.write(imageData);
int responseCode = this.connection.getResponseCode();
if(responseCode != HttpConnection.HTTP_OK) {
throw new IOException("Transmission failed as server responded with response code: " + responseCode);
}
// process response here...
I've found some sollutions online for handling a post request from a j2me application which doens't do what I want and it's in VB. But maybe there's some useful code in there, which should be placed in the page-load event:
' the stream will be ASCII encoded'
Dim ascii As ASCIIEncoding = New ASCIIEncoding
'Get ASCII into reg. string here'
strmContent = ascii.GetString(strArr)
Label1.Text = strArr.ToString()
'write the received data to a text file'
Dim FILE_NAME As String = "C:\\NP\\received.txt"
Dim objWriter As New System.IO.StreamWriter(FILE_NAME, True)
objWriter.WriteLine(strmContent)
objWriter.WriteLine()
objWriter.Close()
I have no clue how I can receive the image data on my website. What code do I need to put in my Controller Action to be able to receive all the data? Do I need to change anything in my application code?
I'm splitting up the simple data from the image data. Is that even the right way to work here?
Thanks alot!

Answer 1

I am not an expert of j2me but you could simply make a multipart/form-data request as shown in this article which allows you to send files in addition to simple values in an HTTP request. So your code will look something along the lines of:
byte[] fileBytes = DataModel.getImageData();
Hashtable params = new Hashtable();
params.put("Description", "some description");
params.put("Latitude", "5");
params.put("Longitude", "6");
params.put("Timestamp", "123");
params.put("UserName", "john smith");
HttpMultipartRequest req = new HttpMultipartRequest(
"http://example.com/home/upload",
params,
"Image", "original_filename.png", "image/png", fileBytes
);
byte[] response = req.send();
Then on your ASP.NET MVC side your view model will simply look like this:
public class MyViewModel
{
public string Description { get; set; }
public float Latitude { get; set; }
public float Longitude { get; set; }
public long Timestamp { get; set; }
public string UserName { get; set; }
public HttpPostedFileBase Image { get; set; }
}
and your controller action:
[HttpPost]
public ActionResult Upload(MyViewModel model)
{
...
}
And here's the HttpMultipartRequest code (in case Nokia's site goes down):
import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Enumeration;
import java.util.Hashtable;
import javax.microedition.io.Connector;
import javax.microedition.io.HttpConnection;
public class HttpMultipartRequest
{
static final String BOUNDARY = "----------V2ymHFg03ehbqgZCaKO6jy";
byte[] postBytes = null;
String url = null;
public HttpMultipartRequest(String url, Hashtable params, String fileField, String fileName, String fileType, byte[] fileBytes) throws Exception
{
this.url = url;
String boundary = getBoundaryString();
String boundaryMessage = getBoundaryMessage(boundary, params, fileField, fileName, fileType);
String endBoundary = "\r\n--" + boundary + "--\r\n";
ByteArrayOutputStream bos = new ByteArrayOutputStream();
bos.write(boundaryMessage.getBytes());
bos.write(fileBytes);
bos.write(endBoundary.getBytes());
this.postBytes = bos.toByteArray();
bos.close();
}
String getBoundaryString()
{
return BOUNDARY;
}
String getBoundaryMessage(String boundary, Hashtable params, String fileField, String fileName, String fileType)
{
StringBuffer res = new StringBuffer("--").append(boundary).append("\r\n");
Enumeration keys = params.keys();
while(keys.hasMoreElements())
{
String key = (String)keys.nextElement();
String value = (String)params.get(key);
res.append("Content-Disposition: form-data; name=\"").append(key).append("\"\r\n")
.append("\r\n").append(value).append("\r\n")
.append("--").append(boundary).append("\r\n");
}
res.append("Content-Disposition: form-data; name=\"").append(fileField).append("\"; filename=\"").append(fileName).append("\"\r\n")
.append("Content-Type: ").append(fileType).append("\r\n\r\n");
return res.toString();
}
public byte[] send() throws Exception
{
HttpConnection hc = null;
InputStream is = null;
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] res = null;
try
{
hc = (HttpConnection) Connector.open(url);
hc.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + getBoundaryString());
hc.setRequestMethod(HttpConnection.POST);
OutputStream dout = hc.openOutputStream();
dout.write(postBytes);
dout.close();
int ch;
is = hc.openInputStream();
while ((ch = is.read()) != -1)
{
bos.write(ch);
}
res = bos.toByteArray();
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
try
{
if(bos != null)
bos.close();
if(is != null)
is.close();
if(hc != null)
hc.close();
}
catch(Exception e2)
{
e2.printStackTrace();
}
}
return res;
}
}