Sending Multipart Form Data from Java (and receiving it via PHP)

If you want to send binary data and some parameters, you'll need to execute a POST with the content type of multipart/form-data. This takes a different format than usual HTTP requests. The secret to sending multipart form data is sending the right number of line endings. Rather than explain it, here's the code.

String lineEnd = "\r\n"; 
String twoHyphens = "--"; 
String boundary =  "*****"; 
int bytesRead, bytesAvailable, bufferSize; 
byte[] buffer; 
int maxBufferSize = 1*1024*1024; 
File temp_file = new File("foo.txt");
// open a URL connection 
URL url = new URL(urlString); 

// Open a HTTP connection to the URL 
conn = (HttpURLConnection) url.openConnection(); 

// Allow Inputs 
conn.setDoInput(true); 

// Allow Outputs 
conn.setDoOutput(true); 

// Don't use a cached copy. 
conn.setUseCaches(false); 

// Use a post method. 
conn.setRequestMethod("POST"); 
conn.setRequestProperty("Connection", "Keep-Alive"); 
conn.setRequestProperty("Content-Type", "multipart/form-data;boundary="+boundary); 

dos = new DataOutputStream( conn.getOutputStream() ); 

// Send parameter #1
dos.writeBytes(twoHyphens + boundary + lineEnd); 
dos.writeBytes("Content-Disposition: form-data; name=\"param1\"" + lineEnd + lineEnd);
dos.writeBytes("foo1" + lineEnd);

// Send parameter #2
dos.writeBytes(twoHyphens + boundary + lineEnd); 
dos.writeBytes("Content-Disposition: form-data; name=\"param2\"" + lineEnd + lineEnd);
dos.writeBytes("foo2" + lineEnd);

// Send a binary file
dos.writeBytes(twoHyphens + boundary + lineEnd); 
dos.writeBytes("Content-Disposition: form-data; name=\"uploadedfile\";filename=\"" + temp_file.getName() +"\"" + lineEnd); 
dos.writeBytes(lineEnd); 

// create a buffer of maximum size 

bytesAvailable = fileInputStream.available(); 
bufferSize = Math.min(bytesAvailable, maxBufferSize); 
buffer = new byte[bufferSize]; 

// read file and write it into form... 

bytesRead = fileInputStream.read(buffer, 0, bufferSize); 

while (bytesRead > 0) 
{ 
 dos.write(buffer, 0, bufferSize); 
 bytesAvailable = fileInputStream.available(); 
 bufferSize = Math.min(bytesAvailable, maxBufferSize); 
 bytesRead = fileInputStream.read(buffer, 0, bufferSize); 
} 

// send multipart form data necesssary after file data... 

dos.writeBytes(lineEnd); 
dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd); 

// close streams 
fileInputStream.close(); 
dos.flush(); 
dos.close();

Ok, now how to read this on the other end? Here's how to do it via PHP:

// Make sure a binary file is attached to the POST
        if(!$_FILES) {
         echo "No file!"
        }
        
        $id = $_FILES['uploadedfile']['name'];
        move_uploaded_file($_FILES['uploadedfile']['tmp_name'], "/permanent/location".$id);
        
        // Uncomment next line to print out the array to a file
        // file_put_contents("/permanent/location/".$id.".debug.txt", print_r($_POST, true));
        $param1="";       
        $param2="";
     if(isset($arguments['param1'])) {
            $lat = $arguments['param1']; 
        }
        if(isset($arguments['param2'])) {
            $lon = $arguments['param2'];
        }
        echo "Uploaded " . $id . " with param1=" . $param1 . " and param2=" . $param2;