Making an HTTP Connection to a Web Server Using
Java[tm] 2 Platform, Micro Edition CLDC and MIDP

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SECTION A - Short Description/Synopsis

The following code example may contain actual software programs in source code form. This source code is made available for developers to use as needed, pursuant to the terms and conditions of this license.

With the Java[tm] 2 Platform, Micro Edition (J2ME[tm]) Connected Limited Device Configuration (CLDC) 1.0.3 and MIDP (Mobile Information Devices Profile) 1.0.3, making an HTTP connection to a webserver involves using the Generic Connection framework and the javax.microedition.io.* package of MIDP. All CLDC/MIDP implementations must implement the HTTP connection protocol according to the specifications. What this means is that for an HTTP connection in a CLDC/MIDP application, one would use the HttpConnection interface as defined in the javax.microedition.io.* package,  which extends the interface javax.microedition.io.ContentConnection.

This document is intended to simply demonstrate the use of the HttpConnection interface to make a connection to a URL.
Therefore, it does not contain additional code for user interface design and hence, does not implement the CommandListener.
The code sample opens up an HTTP connection to the URL, obtains the data through an InputStream, and then
displays the raw HTML content onto the screen console.

NOTE: This code sample will compile and preverify successfully. However, if the code is tested with a
CLDC/MIDP emulator environment, connecting and using the InputStream()method to get a large amount of HTML
or a large file on a webserver may cause the emulator environment to run out of application memory and will output
this error::

java.lang.OutOfMemoryError
 at com.sun.midp.midlet.Scheduler.schedule(+328)
 at com.sun.midp.dev.DevMIDletSuiteImpl.schedule(+7)
 at com.sun.midp.Main.runLocalClass(+20)
 at com.sun.midp.Main.main(+68)
 

SECTION B - Task and Skeleton code

I. Task List

1. Import the relevant MIDP classes (a) javax.microedition.midlet and (b) javax.microedition.io.
2. Initialise a global string object with the desired URL to connect to. Starting with the startApp() function that the Java application manager calls:
3. Initialise a String buffer object.
4. Create an HttpConnection based on the URL String created in task (2).
5. Create an InputStream object from the HttpConnection established above.
6. Read in the byte stream data until the end of the file when a -1 is returned by the InputStream method,while appending to the data to the String buffer object.
7. Close the InputStream.
8. Close the HttpConnection connection.
9. Convert the data in the buffer using the toString() method and print out onto the system console.
10. Run the pauseApp() method.
11. Exit the application with the destroyApp() method.

Check the emulator message output screen or system console. The raw HTML content of the URL should be displayed by the System.out.println() method.

II. Skeleton Code

}

SECTION C - Source Code

public class MakeHttpConnection extends MIDlet {

    private String URL   = "http://www.foobar.com/index.html";

    public void startApp() {

        //creates a new String buffer object and setting the HTTP connection object to null
        StringBuffer buffer = new StringBuffer();
        HttpConnection c = null;

        try {

            // Display message that code is in startApp()

            System.out.println("In startApp .....\n\n");

            // Open an HTTP connection to the URL. The connection supports
            // the HTTP 1.1 protocol defined in the IETF RFC2616.

            c = (HttpConnection)Connector.open(URL);

            // Open the InputStream using the HTTP connection that
            // was established.
            //
            // Read the data until the end of the file where a -1 is returned.

            InputStream is = c.openInputStream();

            // Append the byte data into the String buffer.

            int ch;

            while ((ch = is.read()) != -1) { buffer.append( (char)ch );}

            // Close the InputStream.

            is.close();

            // Close the HTTP connection

            c.close();

            // Prints out the data read from the URL

            System.out.println( "String read from the URL is: \n\n" + buffer.toString() );

            pauseApp();

        }

        catch ( IOException e ) {

        }

    }

    public void pauseApp() {

       System.out.println("In pauseApp .....\n\n");
       destroyApp( true );
       notifyDestroyed();

    }

    public void destroyApp( boolean unconditional ) {

        System.out.println("In destroyApp .....\n\n");

    }

}