About applications
A PowerBuilder application can be one
of many types of applications:
- Executable
application A collection of PowerBuilder windows that perform related activities
and that you deliver to users.
An executable application can be a traditional client/server
application (that accesses a server database); an application that
acts as a client in a distributed application (and requests services
from a server application); or a server application in a distributed
PowerBuilder application. - Server application A component containing one or more custom class user objects
that have methods to provide the required business logic and the
characteristics needed for deployment to a distributed application server
such as Jaguar CTS. - Internet application A PowerBuilder window or DataWindow running in a web browser.
PowerBuilder includes Internet Tools that let you build web-based applications
and extend existing applications to the Internet. For information,
see Using the PowerBuilder Internet Tools
.
Every application has an Application object.
The Application object is the entry point into the application.
It is a discrete object that is saved in a PowerBuilder library, just
like a window, menu, function, or DataWindow object. When a user
runs the application, the scripts you write for events are triggered
in the Application object.
The Application object defines application-level
properties (such as which fonts are used by default for text) and
application-level behavior (such as what processing should occur
when the application begins and ends).
Events in the Application object
When a user runs an application, an Open event
is triggered in the Application object. The script you write for
the Open event initiates the activity in the application. Typically
it sets up the environment and opens the initial window. For a server
application, the initial window may be the only visual part of the application
since the application’s purpose is to provide the services
requested by client applications.
When a user ends an application, a Close event
is triggered in the Application object. The script you write for
the Close event usually does all the cleanup required, such as closing
a database or writing a preferences file.
If there are serious errors during execution,
a SystemError event is triggered in the Application object.