What the Web DataWindow is
The Web DataWindow generates a DataWindow in HTML. It offers
a thin-client solution that provides most of the data manipulation, presentation,
and scripting capabilities of the PowerBuilder DataWindow without
requiring any PowerBuilder DLLs or plugins on the Web client. The DataWindow
that displays in the Web browser looks very much like the DataWindow
you designed in the DataWindow painter.
HTML DataWindow The Web DataWindow was formerly called the HTML DataWindow;
both terms refer to the same technology.
The simplest way to use the Web DataWindow is to place a Web DataWindow DTC on
a Web page template in a Web target. You can find more information
about using the Web DataWindow DTC in the Working with Web Targets
book.
How the Web DataWindow works
The Web DataWindow uses a component running in a transaction
server (such as EAServer or MTS) cooperating with a dynamic page
server (such as PowerDynamo or Microsoft Active Server Pages in IIS)
and communicating with a Web client via a Web server.
PowerDynamo Personal Web Server PowerDynamo provides a Personal Web Server for use during
development. In production, you can use any Web server that uses
CGI, NSAPI, or ISAPI with the PowerDynamo dynamic page server.
The server component can also be called directly from PowerDynamo or
ASP without a transaction server, but using a transaction server
usually provides better performance because database connections
and instances of the component can be pooled or cached.
Changing the component pooling property During development, you may want to turn pooling off. Otherwise
your transaction server will hold onto its connection to your DataWindow
objects, preventing you from modifying them without stopping and
restarting the server. For information on changing the pooling property
of a component, see your server documentation.
When you have developed and deployed the pieces the Web DataWindow needs,
here is what happens:
- In a Web browser, a user requests
the URL for a page. - The Web server passes the request to the page server,
which locates the template for the requested page and executes server-side
scripts in the template. - The server-side scripts connect to the server component,
passing it information about the DataWindow and the database connection. - Methods on the server component retrieve data required
for the DataWindow from the database and translate the DataWindow
definition, data, and state into HTML and JavaScript. - The server component returns the HTML and JavaScript
to the page server. - The page server replaces the server-side script
in the requested Web page with the generated HTML and JavaScript
and returns the page to the Web browser via the Web server. - The user interacts with the DataWindow–for
example, requesting the next page or updating the data. - The Web server passes the URL with added action
parameters to the page server, and the cycle begins again.
The Web DataWindow server component and client control
The Web DataWindow has two main components: the server component
and the client control.
Server component
The Web DataWindow server component retrieves data from a
database and returns HTML and JavaScript that represent the data
and the DataWindow object definition to the page server. The server
component is a PowerBuilder custom class user object that uses a
DataStore to handle retrieval and updates and is deployed as an EAServer or
COM component. You can use the generic component provided with PowerBuilder
or a custom component.
The generic EAServer component, HTMLGenerator90, is preinstalled
in EAServer in a package named DataWindow
.
PowerBuilder also provides a generic COM component called PowerBuilder.HTMLDataWindow
that
you can register and use with IIS, MTS, or EAServer. The COM component
is in the file PBDWR90.DLL. For information
about using the COM component, see “Server configuration details”.
Using an older version of the generic component An earlier version of the generic component, HTMLGenerator,
is also installed in the EAServer DataWindow package. Because EAServer
supports multiple PowerBuilder VMs, you can continue to run older
Web DataWindow applications that use this component.
The generic component has methods that you call in your Web
page template to instantiate and configure the component. It also
provides most of the methods available on the PowerBuilder DataWindow
control. You should probably use the generic component when you
are getting started with the Web DataWindow. Later you may want
to build and deploy a custom component that uses the methods of
the generic EAServer component interface or that uses only the
methods you design for the component. See “Using a custom server component”.
The following table displays all types of DataWindow server
components:
| DataWindow server component | Platform (server component name) | Description |
|---|---|---|
| Generic | EAServer (DataWindow::HTMLGenerator90) or COM (PowerBuilder.HTMLDataWindow) |
Prebuilt (Generic COM component is prebuilt ActiveX). No generation or compiling of stubs required |
| Container (can include multiple DataWindow definitions) | EAServer (PackageName::ComponentName using generic DataWindow::HTMLGenerator90 interface) |
Deploy with Web DW Container project wizard. Increases performance by reducing calls to server. No generation or compiling of stubs required |
| Custom (hybrid) | EAServer (PackageName::ComponentName using generic DataWindow::HTMLGenerator90 interface) |
Use to increase flexibility of generic component. Can build and deploy with PB object or project wizard. Generic methods remain available |
| Custom (user-designed) | EAServer (PackageName::ComponentName) or COM (PackageName.ComponentName) |
Potentially best for performance and scalability. Can use to avoid downloads of unneeded generic methods to client |
Client control
Embedding client-side scripts The Web DataWindow client control is the JavaScript and HTML
that is generated by the server component and embedded in the page
returned to the Web client. Client-side scripts that you add to
your Web page template and wrap in SCRIPT tags are embedded as JavaScript
in the client control.
JavaScript caching Some features available on the client control are optional:
events, methods, data update and validation, and display formatting for
newly-entered data. The size of the generated JavaScript increases
as you add more client-side functionality. You can cache client-side
methods in JavaScript files on your Web server, reducing the size
of the HTML generated for Web DataWindow pages and improving performance
on the client machine if the browser is configured to use cached
files.
For information on enabling JavaScript caching, see “Using JavaScript caching
for Web DataWindow methods” and the discussion
of HTMLGen properties in the DataWindow Reference
.
Using client-side events Events that are triggered on the client control and several
of the client control methods do not require the server component
to reload the page, so processing on the client is typically much
faster than processing performed on the server.
For more information about enabling features on the client,
see “Setting HTML properties
in the DataWindow painter” and “Controlling what HTML is
generated “. For more
about writing scripts, see “Writing client-side scripts”.
For complete documentation of the events and methods available
on the server component and the client control, see the DataWindow
Reference
or the PowerBuilder or DataWindow Builder online
Help.