When a channel policy check rejects (PolicyResult.accept==false) a request, the UDTT Channel driver will throw the com.ibm.btt.channel.ChannelPolicyException exception. By default, the UDTT presentation handler returns the exception to the client end. But a more user friendly error message to client end might be more appropriate. In this case, a technical developer must extend the channel presentation handler to handle the exception.

For example, in the HTML channel, the default presentation handler is

or

To handle exceptions according to the requirements of specific applications, technical developers must extend either of the above presentation handlers and override the handleException method.

In the method, the presentation handler handles any exception that is thrown while processing the request, and navigates a user to the proper error page with a proper message. Below is an example of the handleException method implementation to demonstrate how to handle ChannelPolicyException.

To apply the new presentation handler, technical developers must configure this presentation handler in the btt.xml file for the channel.