Why PHP with J2ME

You my have noticed in last year or two there has been an increasing boom in technology in the area of mobile handsets and mobile software development. Wireless technology is not only becoming more commonplace but also more affordable. To support this even further a survey released by IDC projected revenues in wireless gaming alone will approximately generate 72.2 million by 2007. Along side with mobile gaming there will ever increase in demand for mobile applications.

Okay this is fine and dandy, but what does this have to do with PHP? Not only will there be thousands of new wireless applications but many existing applications of today will now be enhanced/modified to work with mobile handsets. In most cases it would make sense to keep the current technology and architecture and simply have it interface with the new mobile technology. Possibly meaning sites already written in PHP now need to interact with the mobile technology, one of the more popular emerging technologies is J2METM. J2METM is provided by Sun Microsystems and stands for Java 2 Platform Micro Edition. To learn more about J2METM and Java general visit http://java.sun.com. J2METM produces small Java applications or games called midlets. A very simple description would be midlets are to wml like the Java applets are to HTML. Though midlets do not run directly inside of wml, you would access/download a midlet through a wml browser. As well you do have the option to directly upload the midlet to your mobile handset via PC and cable connector.

There are few options available when considering how to communicate PHP with J2ME:

· HTTP Simple Fetch
· HTTP GET/POST
· Web Services
· Fetching Images

Requirements

This article uses both J2METM and PHP. You will need the J2ME TM Development kit from http://wireless.java.sun.com and PHP from http://www.php.net. As well you need to install php with a web server, in this article I will be using Apache. Apache can be obtained from http://www.apache.org. Please consult theses sites for installation instructions. Once you?ve successfully installed the software continue with the article.

Simple HTTP Fetch
Here is a simple example of fetching information in text file.

J2ME Source Code:

import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class SimpleFetch extends MIDlet {

private Display display;

String url = "http://127.0.0.1/midlet/helloworld.txt";

public SimpleFetch() {
display = Display.getDisplay(this);
}

public void startApp() {
try {
getViaStreamConnection(url);
} catch (IOException e) {
//Handle Exceptions any other way you like.
System.out.println("IOException " + e);
e.printStackTrace();
}
}
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }

/**
* Read URL as Stream
*/
void getViaStreamConnection(String url) throws IOException {
StreamConnection streamConnection = null;
InputStream inputStream = null;
StringBuffer b = new StringBuffer();
TextBox textBox = null;
try {
streamConnection = (StreamConnection)Connector.open(url);
inputStream = streamConnection.openInputStream();
int ch;
while((ch = inputStream.read()) != -1) {
b.append((char) ch);
}
textBox = new TextBox("Simple URL Fetch", b.toString(), 1024, 0);
} finally {
if(inputStream != null) {
inputStream.close();
}
if(streamConnection != null) {
streamConnection.close();
}
}
display.setCurrent(textBox);
}
}

PHP Source Code:
In this case there really is not source code, only a text file with the following contents

Hello World!
by Jason Lam

The name of the text file as indicated in the J2ME code is helloworld.txt.

Simple HTTP GET
Here is an example invoking a PHP with GET parameters.

J2ME Source Code:
import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;
import javax.microedition.midlet.*;

public class SimpleGETExample extends MIDlet {

private Display display;

String url = "http://127.0.0.1/midlet/testGET.php?type=2";

public SimpleGETExample() {
display = Display.getDisplay(this);
}

public void startApp() {
try {
testGET(url);
} catch (IOException e) {
System.out.println("IOException " + e);
e.printStackTrace();
}
}

public void pauseApp() { }
public void destroyApp(boolean unconditional) { }

void testGET(String url) throws IOException {
HttpConnection connection = null;
InputStream is = null;
OutputStream os = null;
StringBuffer stringBuffer = new StringBuffer();
TextBox textBox = null;

try {
connection = (HttpConnection)Connector.open(url);
connection.setRequestMethod(HttpConnection.GET);
connection.setRequestProperty("IF-Modified-Since","20 Jan 2001 16:19:14 GMT");
connection.setRequestProperty("User-Agent","Profile/MIDP-2.0 Confirguration/CLDC-1.0");
connection.setRequestProperty("Content-Language", "en-CA");
connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
os = connection.openOutputStream();
is = connection.openDataInputStream();
int ch;
while ((ch = is.read()) != -1) {
stringBuffer.append((char) ch);
}
textBox = new TextBox("Simple GET Test", stringBuffer.toString(), 1024, 0);
} finally {
if(is!= null) {
is.close();
}
if(os != null) {
os.close();
}
if(connection != null) {
connection.close();
}
}
display.setCurrent(textBox);
}
}

PHP Source Code:
$response = "Hello";

if (isset($_GET)) {
switch ($_GET["type"]) {
case 1: $response = "Good Morning"; break;
case 2: $response = "Good Afternoon"; break;
case 3: $response = "Good Evening"; break;
default: $response = "Hello"; break;
}
}
echo $response;
?>

Depending on what the midlet sends to the testGET.php script in the GET parameter different results are returned. If you are already familiar with using GET and POST, you can see that there isn't really much of difference, it is quite trivial.

Extra Note:
The results would be the same if you decided to make a POST call instead of a GET call, of course both the J2ME and PHP source code would have to be changed accordingly to handle POST instead of GET.

Simple WebService

You probably know you can provide web services with PHP and NuSoap. One of the great the advantages a web service is the fact that it provides independence from operating systems and platforms. To learn more about web services refer to Ahm Asaduzzaman?s excellent article on Building XML Web Services with PHP NuSOAP published at http://www.devbuilder.org/asp/dev_article.asp?aspid=12

In this example you will also need the appropriate libraries for the midlet to run correctly:
· kSOAP - http://ksoap.enhydra.org/
· kXML - http://kxml.org

In this example we are using the 1.x versions of kSOAP and kXML.

J2ME Source:
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.io.*;
import javax.microedition.io.*;

import org.ksoap.*;
import org.ksoap.transport.*;
import org.ksoap.SoapObject;

public class SimpleWebService extends javax.microedition.midlet.MIDlet {
private Display display;
private String url = "http://127.0.0.1/midlet/webservice/service.php";
TextBox textbox = null;

public SimpleWebService() {
display = Display.getDisplay(this);
}

public void startApp() {
try {
testWebService();
} catch (Exception ex) {
System.out.println(ex);
}
}

public void pauseApp() {
}

public void destroyApp(boolean unconditional) {
}

public void testWebService() throws Exception {
StringBuffer stringBuffer = new StringBuffer();

TextBox textBox = null;

// First WebService - echos name that is passed in, in this case 'Jason'
SoapObject client = new SoapObject(url,"hello");
client.addProperty("name","Jason");
HttpTransport ht = new HttpTransport(url,"hello");
stringBuffer.append(ht.call(client));

// 2nd WebService - Supply 2 numbers and the result is the sum of the
// two numbers
client = new SoapObject(url,"add");
client.addProperty("x","7");
client.addProperty("y","6");
ht = new HttpTransport(url,"add");
stringBuffer.append("\nAdd Result: " + ht.call(client));

// display results in textbox
textBox = new TextBox("Simple WebService Test", stringBuffer.toString(), 1024, 0);
display.setCurrent(textBox);
}
}

PHP Source Code:
// include NuSOAP library
require_once('nusoap.php');

// Create Web Service Server
$server = new soap_server;

// Register Services
$server->register('hello');
$server->register('add');

// Define Services
function hello ($name){
return "Hello $name";
}

function add ($x,$y){
return $x + $y;
}

$server->service($HTTP_RAW_POST_DATA);
?>

Was that not easy or what? The beauty of this is now you can easily interface your new PHP web service(s) with any device, whether it be WebTV/iTV, SIP device, mobile device running something else other then J2ME (Symbian, PalmOS, MoPhun, Brew,MS SmartPhone) or voice enabled only.

Simple Image Fetch

You can even retrieve binary data such as images. If the mobile device is capable of view documents like word or PDF you should be able to send those by HTTP as well.

J2ME Source Code:
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import javax.microedition.io.*;
import java.io.*;

public class SimpleImageFetch extends MIDlet
{
private Display display;
private String URL = "http://127.0.0.1/midlet/image/test.php";
private Form formImage;

public SimpleImageFetch()

{
try {
display = Display.getDisplay(this);
Image im = getImage(URL);
formImage = new Form("Simple Image Test");
formImage.append(im);
display.setCurrent(formImage);
} catch (Exception ex) {
System.out.println(ex);
}

}

public void startApp() { }
public void pauseApp() { }
public void destroyApp(boolean unconditional) { }

private Image getImage(String url) throws IOException
{
ContentConnection connection = (ContentConnection) Connector.open(url);
DataInputStream iStrm = connection.openDataInputStream();
Image im = null;

try {
byte imageData[];
ByteArrayOutputStream bStrm = new ByteArrayOutputStream();
int ch;
while ((ch = iStrm.read()) != -1)
bStrm.write(ch);
imageData = bStrm.toByteArray();
bStrm.close();
im = Image.createImage(imageData, 0, imageData.length);
} finally {
if (iStrm != null)
iStrm.close();
if (connection != null)
connection.close();
}
return (im == null ? null : im);
}
}

PHP Source Code:
$filename = "./phpjava.png";
$handle = fopen ($filename, "rb");
$contents = fread ($handle, filesize ($filename));
fclose ($handle);
header("Content-type: image/gif");
header("Content-length: ".(string)(filesize($filename)));
echo $contents
?>

Beyond Basic HTTP Communication

In general, we?ve only dealt with basic HTTP communications. There are other methods of communication you may want to consider as well when using PHP, like SMS, email or sockets.

Remember the above examples are very simplistic and are meant for demonstration purpose only. For more production ready code you should be aware of the:

· The way J2ME handles Session and Cookies
· J2ME and PHP page caching
· Detection of HTTP_USER_AGENT
· Encryption, Base64, MD5, Bouncy Castle ( http://www.bouncycastle.org ) with MIDP 2 comes with PKI support
· Latency,
· Size data being transferred,
· Frequency of data being transferred

The listed above things to beware of is really only related to the communication aspect. There are other considerations that out the scope from this document such as performance, data persistence and porting constraints to name a few.

Summary