HTTP Post multipart file upload in Java ME

Here is a J2ME class to handle file uploads via HTTP POST Multipart Requests.

Source Code: HttpMultipartRequest class

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;
	}
}

Sample usage

Here's a code snippet to upload a file via HttpMultipartRequest class:

byte[] fileBytes = getFileBytes(); //retrieve file bytes with your own code
 
Hashtable params = new Hashtable();
params.put("custom_param", "param_value");
params.put("custom_param2", "param_value2");
 
HttpMultipartRequest req = new HttpMultipartRequest(
	"http://www.server.com/uploadScript.php",
	params,
	"upload_field", "original_filename.png", "image/png", fileBytes
);
 
byte[] response = req.send();

Sample server code (PHP)

This is a sample PHP script that handles the upload. It doesn't actually save the uploaded file, but only displays some infos about the upload size and parameters.

<?php
 
$filesize = filesize($_FILES['upload_field']['tmp_name']);
 
echo "The uploaded file size is " . $filesize . " bytes\n";
 
foreach($_POST as $key => $value)
{
	echo "Parameter name: " . $key . ", value: " . $value . "\n";
}
 
?>

Link: http://www.developer.nokia.com/Community/Wiki/HTTP_Post_multipart_file_upload_in_Java_ME