How to call HTTP URL using wifi in J2ME code for BlackBerry 5.0 and above?

Question

I am calling a web service from BlackBerry using J2ME code. When I try to open a connection using HttpConnection, it is checking only the GPRS connection. Now, I want to check the Wi-Fi connection and call a webservice through Wi-Fi.

The following code is my connection section. How to change the code for a Wi-Fi connection?

public boolean HttpUrl() 
{
    HttpConnection conn = null;
    OutputStream out = null;
    String url = "http://www.google.com";
    try 
    {
        conn = (HttpConnection) new ConnectionFactory().getConnection(url).getConnection();
        if (conn != null) 
        {

            conn.setRequestMethod(HttpConnection.POST);
            conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");
            conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
            conn.setRequestProperty("User-Agent", "Profile/MIDP-2.0 Configuration/CLDC-1.0");


        }
    } 
    catch (Exception e) 
    {
        return false;
    } 
    finally 
    {
        try 
        {
            out.close();
        } 
        catch (Exception e2) 
        {
        }
    }

    //Only if exception occurs, we close the connection.
    //Otherwise the caller should close the connection himself.
    try 
    {
        conn.close();
    } 
    catch (Exception e1)
    {
    }
    return true;
}

Answer 1

Check this way:

HttpConnection conn = null;
String URL = "http://www.myServer.com/myContent;deviceside=true;interface=wifi";
conn = (HttpConnection)Connector.open(URL);

source

Answer 2

Making Connections

Rafael's answer will certainly work if you know you'll only be using Wi-Fi.

However, if you only need to support BlackBerry OS 5.0 - 7.1, I would recommend that you do use the ConnectionFactory. Normally, you will not limit your code to only using one transport. You'll normally support (almost) any transport the device has, but you may want to code your app to choose certain transports first.

For example,

class ConnectionThread extends Thread
{
    public void run()
    {
        ConnectionFactory connFact = new ConnectionFactory();
        connFact.setPreferredTransportTypes(new int[] { 
                TransportInfo.TRANSPORT_TCP_WIFI,
                TransportInfo.TRANSPORT_BIS_B,
                TransportInfo.TRANSPORT_MDS,
                TransportInfo.TRANSPORT_TCP_CELLULAR
        });
        ConnectionDescriptor connDesc;
        connDesc = connFact.getConnection("http://www.google.com");
        if (connDesc != null)
        {
            HttpConnection httpConn;
            httpConn = (HttpConnection)connDesc.getConnection();
            try
            {
                // TODO: set httpConn request method and properties here!
                final int iResponseCode = httpConn.getResponseCode();
                UiApplication.getUiApplication().invokeLater(new Runnable()
                {
                    public void run()
                    {
                        Dialog.alert("Response code: " + 
                                Integer.toString(iResponseCode));
                    }
                });
            } 
            catch (IOException e) 
            {
                System.err.println("Caught IOException: " 
                        + e.getMessage());
            }
        }
    }
}    

will choose the Wi-Fi transport if Wi-Fi is available, but use the GPRS connection if it isn't. I think this is generally considered best practice for the 5.0+ devices.

Request Properties

This code

conn.setRequestProperty("Content-Length", "application/x-www-form-urlencoded");

is not right. Content-Length should be the size, in bytes, of your HTTP POST parameters. See an example here.

Threading

Remember that making network connections is slow. Do not block the user interface by running this code on the main/UI thread. Put your code into a background thread to keep the UI responsive while you request remote content.