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

I hope this helps . So here's what I ended up doing so far: Declawer + some custom code for enumeration classes generation.
The one differentiating thing about Declawer is that, although it's very simple and, frankly, a bit of a hack (it relies on an undocumented capability of JavaC), its output is actual Java code as compared to enhanced or converted Java bytecode. That's very precious for mobile java-based development as, frankly, bytecode modification/instrumentation is not at all as developed for j2me platforms as it is for j2se, and there are just no guarantees that things are going to work out of the box the way they do with j2se where these tools have already been used by quite a few developers.

should help you out you can use something like this (you probably need to setup correct request headers and cookies):

        connection = (HttpConnection) Connector.open(url
                + ConnectionUtils.getConnectionString(), Connector.READ_WRITE);

        connection.setRequestProperty("ajax","true");                       
        connection.setRequestProperty("Cookie", "JSESSIONID=" + jsessionId);

        inputStream = connection.openInputStream();

        byte[] responseData = new byte[10000];
        int length = 0;
        StringBuffer rawResponse = new StringBuffer();
        while (-1 != (length = inputStream.read(responseData))) {
            rawResponse.append(new String(responseData, 0, length));
        }
        int responseCode = connection.getResponseCode();
        if (responseCode != HttpConnection.HTTP_OK) {
            throw new IOException("HTTP response code: " + responseCode);
        }

        responseString = rawResponse.toString();

this will help You can use the Radio.activateWAFs() method to do this, if you pass WAF_WLAN as a parameter. You can use it to enable or disable each wireless connection on the device.

it fixes the issue To handle BB events, you'll have to import net.rim... libraries instead of javax.microedition..., which means you'll have to write event handling again. J2ME event handlers are different from BB's and BB does not recognize them. So you can run a jar file in a BB but you can not have the complete functionality.