What the Web DataWindow is
The Web DataWindow is a DataWindow that is generated for use
in Web applications. The Web DataWindow 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 plug-ins on the Web client. The DataWindow that displays
in the Web browser looks very much like the DataWindow you designed
in the DataWindow painter.
Web DataWindow types
The Web DataWindow in PowerBuilder 9 was a Web DataWindow implementation
in HTML that was originally called the HTML DataWindow. In PowerBuilder
10, Web DataWindow functionality has expanded to include three types
of Web DataWindow implementation:
- XML Web DataWindow Separate XML (content), XSLT (layout), and CSS (style) with
a subsequent transformation to XHTML - XHTML Web DataWindow XHTML content only
- HTML Web DataWindow HTML content only
HTML Generation property page has been renamed Since the Web DataWindow can now be generated in XML, XHTML,
and HTML, the HTML Generation property page in the DataWindow properties view
is now called the Web Generation property page. Shared XHTML and HTML
properties and properties specific to XML, XHTML, and HTML can be
set there. For information about setting Web generation properties,
see “Setting Web generation properties
for the Web DataWindow”.
Web DataWindow use
The easiest way to use any type of Web DataWindow involves
placing a Web DataWindow design-time control (DTC) on a Web page
template in a Web target and setting Web DataWindow DTC properties
such as the generation format: XML, XHTML, or HTML.
No matter what type of Web DataWindow you want to use, the
way you use it is the same. For specific information about using
the XML Web DataWindow, see “Using the XML Web DataWindow”. For information about using the Web DataWindow DTC,
see the chapter about the Web DataWindow design-time control
in the Working with Web and JSP Targets
book
and “Setting Web DataWindow design-time
control properties”.
How the Web DataWindow works
The Web DataWindow uses a component running in a transaction
server (such as EAServer or COM+)
cooperating with a dynamic page server (such as Microsoft Active
Server Pages in IIS or Java Server
Pages in Tomcat) and communicating with a Web client by means of
a Web server. No PowerBuilder DLLs or plug-ins are required on the
Web client.
The built-in Web DataWindow component is the HTMLGenerator90 component
that is preinstalled in EAServer 5.1.
The component is used to generate the JavaScript and the HTML; XHTML;
or XML, XSLT, CSS, and XHTML, depending on the type of Web DataWindow
you are creating. You can also use a custom component that you develop
instead. For more information, see “The Web DataWindow server
component and client control” on page .
A DataWindow COM component can also be called directly from
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.
Disabling instance pooling when deploying Web DataWindow
targets Instance pooling allows transaction server clients to reuse
component instances and so improves server performance by eliminating
the resource drain caused by repeated allocation of component instances.
Instance pooling is turned on by default for the HTMLGenerator100
component in EAServer. This prevents you
from deploying a target that uses the component a second time without stopping
and restarting the server. During development, you might want to
turn instance pooling off. For information on changing the pooling
property of a component, see your server documentation.
In EAServer, you can disable instance pooling using EAServer
Manager or you can set the com.sybase.jaguar.component.pooling property
to false in the EAServerRepositoryComponentDataWindow
directory in the HTMLGeneratorXX.props file. The component pooling
property should be set to true for production
use.
What happens when a user requests a page
Figure 6-1 shows
you graphically (in eight steps) what happens when a user accesses
a Web page containing an XHTML or HTML Web DataWindow:
The numbers 1 through 8 in the figure correspond to the events
that occur after you develop and deploy a Web DataWindow and a user
accesses a page containing the Web DataWindow:
- 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 (transaction)
server component, passing it information about the DataWindow and
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 JavaScript and XHTML or HTML. - The server component returns the JavaScript and
XHTML or HTML and to the page server. - The page server replaces the server-side script
in the requested Web page with the generated JavaScript and XHTML
or HTML and returns the page to the Web browser through 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.
Web DataWindow server component
The Web DataWindow server component retrieves data from a
database and returns JavaScript and XSLT, XHTML, or HTML 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 COM+ or EAServer. The COM component is in
the file PBDWR90.DLL. For information
about using the COM component, see “Server configuration requirements”.
Using an older version of the generic component Earlier versions of the generic HTMLGenerator component are
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. The generic
component 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
might 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. For information,
see “Using a custom server component”.
Types of server components and platforms
The following table describes all the types of Web DataWindow
server components and their supported platforms:
| Web DataWindow server component | Platform
(server component name) |
Description |
|---|---|---|
| Generic | EAServer (DataWindow::HTMLGenerator90) or COM (PowerBuilder.HTMLDataWindow) |
Prebuilt EAServer component or prebuilt COM component (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. |
Web DataWindow client control
Embedding client-side scripts The Web DataWindow client control is the JavaScript plus XML,
XSLT, and CSS; the JavaScript plus XHTML; or the JavaScript plus
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 to reduce the size
of the markup generated for Web DataWindow pages and, if the browser
is configured to use cached files, improve the performance on the
client machine.
For information about enabling JavaScript caching, see “Using JavaScript caching
for Web DataWindow methods”. You can find
additional information about client-side caching, HTMLGen properties,
and other generation 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 “Web DataWindow properties” and “Controlling what 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 online Help.