Post.java

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Random;
import java.util.Set;

public class MultipartForm {
	private int mContentLength;
	private String mBoundary;
	private String mCharset;
	private String mPath;
	private HashMap<String, String> mHash;

	public MultipartForm(String charset) {
		mCharset = charset;
		mBoundary = generateBoundary();
	}

	public void ready(HashMap<String, String> hash, String path) throws IOException {
		mHash = hash;
		mPath = path;
		doOutputDummy();
	}

	public String post(String serv) throws IOException {
		URL url = new URL(serv);
		HttpURLConnection conn = (HttpURLConnection) url.openConnection();
		conn.setFixedLengthStreamingMode(mContentLength);
		conn.setRequestMethod("POST");
		conn.setDoOutput(true);
		conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + mBoundary);
		conn.connect();

		OutputStream out = conn.getOutputStream();
		doOutput(out);
		out.flush();
		out.close();

		BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
		String responseData = null;
		StringBuffer buf = new StringBuffer();
		while( (responseData = reader.readLine()) != null ) {
		    buf.append(responseData);
		}
		reader.close();
		conn.disconnect();
		return buf.toString();
	}

	private String generateBoundary() {
	    StringBuffer buf = new StringBuffer();
	    for (int i = 0; i < 29; i++) {
	    	buf.append("-");
	    }
	    String chars = "1234567890";
	    Random rand = new Random();
	    for (int i = 0; i < 29; i++) {
	        int r = rand.nextInt(chars.length());
	        buf.append(chars.substring(r, r + 1));
	    }
	    return buf.toString();
	}

	private void doOutputDummy() throws IOException {
		DummyOutputStream dummy = new DummyOutputStream();
		doOutput(dummy);
		mContentLength = dummy.getSize();
		dummy.close();
	}

	private void doOutput(OutputStream out) throws IOException {
		Set<String> set = mHash.keySet();
		Iterator<String> iterator = set.iterator();
		while (iterator.hasNext()) {
			String key = iterator.next();
		    out.write(("--" + mBoundary + "\r\n").getBytes(mCharset));
		    out.write(("Content-Disposition: form-data; name=\"" + key + "\"\r\n").getBytes(mCharset));
		    out.write(("Content-Type: text/plain; charset=" + mCharset + "\r\n\r\n").getBytes(mCharset));
		    out.write((mHash.get(key)).getBytes(mCharset));
		    out.write(("\r\n").getBytes(mCharset));
		}

		if (mPath != null) {
			out.write(("--" + mBoundary + "\r\n").getBytes(mCharset));
			out.write(("Content-Disposition: form-data; name=\"file\"; filename=\"out.jpg\"\r\n").getBytes(mCharset));
			out.write(("Content-Type: application/octet-stream\r\n\r\n").getBytes(mCharset));
			InputStream in = null;
			byte[] bytes = new byte[1024];
			in = new FileInputStream(mPath);
			if (in != null) {
		        while (true) {
		            int ret = in.read(bytes);
		            if (ret == -1) {
		            	break;
		            }
		            out.write(bytes, 0, ret);
		            out.flush();
		        }
		        in.close();
			}
			out.write(("\r\n").getBytes(mCharset));
		}
	    
	    out.write(("--" + mBoundary + "--").getBytes(mCharset));
	}
}

class DummyOutputStream extends OutputStream {
    private int size = 0;
    
    @Override
    public void write(int b) throws IOException {
        size += 1;
    }

    @Override
    public void write(byte[] bytes) throws IOException {
        size += bytes.length;
    }
 
    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        size += len;
    }
    
    public int getSize(){
        return this.size;
    }
}