AEM detect the device from which the request came?

I want to achieve is, When a mobile device sends the request to the page it captures the attributes of mobile like mobile browser, mobile browser version, mobile OS and mobile OS version. I want to LOG this information and in later stage use this to categorize them in different Device Group and render different components in different device groups.

Note I have already gone through some of these links CQ5 Mobile Development Docs

http://www.cognifide.com/blogs/cq/adobe-cq-5-5-mobile-improvements/http://wurfl.sourceforge.net/help_doc.php

I have tried this code which throws Null Pointer Exception since the device variable has a null value. Correct me if I am doing wrong somewhere

SlingHttpServletRequest slingRequest = this.request.getSlingRequest();Device device = slingRequest.adaptTo(Device.class);     if(device != null) {         DeviceGroup deviceGroup = device.getDeviceGroup();         Collection<DeviceCapability> capabilities = deviceGroup.getCapabilities();         Map<String,String> deviceAttributes = device.getAttributes();         String userAgent = device.getUserAgent();         out.write(userAgent + "  inside if\n");     }     out.write("  Test\n");

Here is the way I am testing this code, whenever a request is sent to the page which has this component which write the attributes of the mobile device. I am using emulators in google chrome.

Please help me out if I am going wrong in the code or method to get the mobile device's attributes. Please let me know if you need more details on this.