The beauty of Adobe AIR is it enables to develop and deploy a Rich Internet Application (RIA) on the desktop. But one interesting scenario which develops when deploying a RIA on the desktop is, how will the application know, if the internet connection is currently available? How to enable run time handling of the application based on the availability of the Internet Connection?

AIR SDK answers all this by providing the developer with the URLMonitor Class. This class which is included in the ServiceMonitor.swc file, provides properties and methods to handle changes in the Internet Connection. The following steps explain, how to make efficient use of the URLMonitor class to check the availability of the Internet Connection.

Step 1: To access the properties and methods of the URLMonitor class we will have to import the air.net.URLMonitor class

import air.net.URLMonitor;

Step 2: Create an object of URLMonitor class.

private var monitor:URLMonitor;

Step 3: Create an URLRequest object and to the constructor pass the URL you wish to be requested

private var myURL:URLRequest = new URLRequest(“http://www.adobe.com”);

Step 4: On Creation Complete of the application, instantiate the URLMonitor object (monitor) by passing the URLRequest object (myURL) as one of the parameters

monitor = new URLMonitor(myURL);

Step 5: Start the URLMonitor by calling the method start()

monitor.start();

Step 6: Add an event listener where the event is of type Status. This indicates that the service status has changed.

monitor.addEventListener(StatusEvent.STATUS, on_Connection);

Step 7: Now the last and the final step. In the filter function on_Connection(event:Event), check if the Internet Connection is available by checking the boolean value of the property “available”.

Reason: When a null value is sent for variable of any data type from Flex, the Cold Fusion handles it differently. In particular, Cold Fusion does not believe in the concept of null and stores it as empty value i.e. If there is a variable by name “dt”. Instead of having dt = null, we will have dt = “” in CF. This creates issues when building Data intensive applications (one of the key focus area of DCD). MySQL associates the concept of nothing to “null” and not to {empty}/””. Only in the case of String does MySQL recognizes {empty}/ “” and stores it as null.

Work Around: Let us look at the following lines of code, to better understand the work around.

a) <cfquery name=”updateItem” datasource=”Test”>

The above lines of code show a sample SQL query in CF. It shows an Update query which tries to set the value of field Start_Date, to the value existing in the variable #item.Start_Date#. In the above code I would like to draw the attention to a specific property in the CFQUERYPARAM, the property “null”.

Above we have set the property null to a variable #dt1#. This property decides if we are passing a null value to the Query or Not

b) Now let us have a look at dt1 variable. dt1 is a CF variable with a boolean value. The Boolean value for that variable is decided on the value present in item.Start_Date. If item.Start_Date is empty then dt1 is true.

Combining a and b. We have the following algorithm:

a) Initialize a CF variable dt1 to false

b) Check if the value present in item.Start_Date = “”

c) If empty, set dt1 to true, else keep it at false

d) In the SQL query set the null property to take the value present in dt1

e) If dt1 is true, then null value is sent to database, else database gets the value in item.Start_Date