Choosing a DataWindow technology
Since DataWindow technology can be used in different environments,
it might not be obvious what approach you should take to implement
your data-enabled application. This section describes the
DataWindow technologies available for three basic application architectures
and the requirements for each DataWindow solution. See Building Internet
and Enterprise Applications
for more discussion of application
architectures.
The basic architectures are:
- Client/server A program running on a client workstation accesses a database
running on a server. The user interface and business logic reside together
on the client computer. - Distributed application The user interface on the client computer calls components
on a middle-tier server, which execute business logic and access
the database server. - Web application A client Web browser sends requests for HTML or JSP documents
to a Web server. The Web server passes control to a page or application
server, where server-side scripts can access components on a transaction
server that can connect to databases on a database server.
Solutions for client/server and distributed
applications
The PowerBuilder DataWindow was initially developed for use
in client/server applications.
You can implement the PowerBuilder DataWindow as a control
that displays a DataWindow object or as a DataStore that supports
data retrieval and update without displaying the data. A complete
set of events and methods programmed in PowerScript provides control
over all aspects of the DataWindow, including data retrieval, display,
validation, and update.
You can also deploy the PowerBuilder DataWindow as a component
for use in distributed applications.
For more information, see “PowerBuilder DataWindow
control”.
Solutions for Web applications
You can use these DataWindow technologies in Web applications:
- Web DataWindow and the Web DataWindow DTC
- Sybase DataWindow Web control for ActiveX
- DataWindow plug-in
Web DataWindow
The Web DataWindow is a thin-client DataWindow implementation
for Web applications. It provides most of the data manipulation,
presentation, and scripting capabilities of the PowerBuilder DataWindow
without requiring any PowerBuilder DLLs on the client.
Functionality
The Web DataWindow supports a subset of the PowerBuilder DataWindow events
and methods, including dynamic modification of the DataWindow object.
The user can modify and update data. Composite, Graph, OLE, and RichText
presentation styles and controls are not supported.
Client requirements
The HTML Web DataWindow works in most browsers, but the appearance
of the generated HTML is usually best in Internet Explorer. Generated
HTML can be dynamically optimized for Netscape or Internet Explorer,
or scaled back to handle older browsers. The XML Web DataWindow
and the XHTML Web DataWindow require the lastest browser technology.
For information about supported browsers, see “Browser requirements for
the XML Web DataWindow”.
Server requirements
A component server and a dynamic page server work together
to generate a client control with data and include it in a Web page.
Each time the user requests a new page of data, updates data, or
inserts or deletes rows, the server gets a request to generate a
new page. Depending on how state is managed, the component might
retrieve data each time it is called, causing added load on the server.
Development tools
The Web Target interface in PowerBuilder provides the Web DataWindow DTC that
you can use to develop Web DataWindows without hand coding. You can
also write your own server-side scripts to create Web DataWindows
using the component server’s API. You can write the scripts
for interpretation by a specific page server type (Active Server
Pages or JavaServer Pages). For Web site targets, you can use the
Web Target object model to write server scripts that are type-neutral—the
scripts can be deployed to Active Server Pages.
When you use the Web DataWindow DTC on a 4GL Web page, server-side events
are available and page variables can enhance the dynamic capabilities of
your Web application. You cannot hand code a Web DataWindow on a
4GL Web page.
For information about the Web DataWindow, see Chapter 6, “Using the Web DataWindow.” For information
about the Web DataWindow DTC, see Working with Web and
JSP Targets
.
Sybase DataWindow Web control for ActiveX
The Sybase DataWindow Web control for ActiveX is an interactive DataWindow
control for use with Internet Explorer that implements all features
of the PowerBuilder DataWindow except rich text.
Functionality
The Web ActiveX is fully programmable and supports DataWindow
events, methods, and dynamic modification of the DataWindow object.
The user can modify and update data. The RichText presentation style
is not supported.
Client requirements
The control uses ActiveX technology and works in Microsoft
Internet Explorer only.
The user must download the CAB file for the component, which
is less than two megabytes in size. Database connection through
JDBC occurs from the client, which must be configured with the connection
software. The software can be downloaded from the Web server.
DataWindow behavior that would compromise security of the
client, such as the SaveAs functionality, is disabled.
Server requirements
The JDBC database connection can access databases on a remote
server.
Development tools
You can use the Web Target tools for working with ActiveX
components to develop your Web application.
For information, see Chapter 8, “Using the DataWindow Web Control
for ActiveX.”
DataWindow plug-in
The DataWindow plug-in is a browser plug-in that displays
Powersoft reports (PSRs).
Functionality
A PSR is a static DataWindow; it cannot be modified and the
data does not stay current. However, a PSR is a compact representation
of the DataWindow definition and data and can be downloaded efficiently.
It is an efficient means of viewing batch-produced reports.
The user cannot modify or update the data.
Client requirements
The plug-in executable must be installed in the browser plug-in
directory. It cannot be downloaded and installed automatically.
The plug-in works in Netscape browsers. Internet Explorer browsers
prior to version 5.5 also support the plug-in.
DataWindow behavior that would compromise security of the
client, such as SaveAs, is not disabled.
Development tools
You can use PowerBuilder or InfoMaker to create PSRs.
For more information about the plug-in architecture, see Application Techniques
.