About this chapter
This chapter describes what DataWindow objects are and the ways you can use them in various application architectures and programming environments.
DataWindow technology is implemented in two parts:
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A DataWindow object
The DataWindow object defines the data source and presentation style for the data.
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A DataWindow control or component
The control or component is a container for the DataWindow object in the application. You write code that calls methods of the container to manipulate the DataWindow object.
DataWindow controls and components
The DataWindow was invented for use in PowerBuilder to provide powerful data retrieval, manipulation, and update capabilities for client/server applications.
You can also use DataStore objects as containers for a DataWindow object. DataStores provide DataWindow functionality for retrieving and manipulating data without the on-screen display. Uses for DataStores include specifying layouts for printing and managing data in the server component of a distributed application.
What DataWindow objects are
A DataWindow object is an object that you use to retrieve, present, and manipulate data from a relational database or other data source (such as an Excel worksheet or dBASE file). You can specify whether the DataWindow object supports updating of data.
DataWindow objects have knowledge about the data they are retrieving. You can specify display formats, presentation styles, and other data properties to make the data meaningful to users.
In the DataWindow painter, you can also make Powersoft report (PSR) files, which you can use in DataWindow controls or components. A PSR file contains a report definition -- essentially a nonupdatable DataWindow object -- as well as the data contained in the report when the PSR file was created. It does not retrieve data.
Where to define DataWindow objects
You define DataWindow objects in the PowerBuilder DataWindow painter. You can also define nonupdatable DataWindow objects in the InfoMaker Report painter.
When you define a DataWindow object, you choose a presentation style and a data source.
Presentation styles
A presentation style defines a typical style of report and handles how rows are grouped on the page. You can customize the way the data is displayed in each presentation style. The presentation styles include:
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Presentation style
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Description
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|---|---|
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Tabular |
Data columns across the page and headers above each column. Several rows are viewable at once. |
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Freeform |
Data columns going down the page with labels next to each column. One row displayed at a time. |
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Grid |
Row-and-column format like a spreadsheet with grid lines. Users can move borders and columns. |
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Label |
Several labels per page with one row for each label. Used for mailing and other labels. |
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N-Up |
Two or more rows of data next to each other across the page. Useful for periodic data, such as data for each day of the week or each month in the quarter. |
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Group |
A tabular style with rows grouped under headings. Each group can have summary fields with computed statistics. |
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TreeView |
A tabular style that groups data hierarchically and displays the data in a way that is collapsible and expandable. |
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Composite |
Several DataWindow objects grouped into a single presentation. |
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Graph |
Graphical presentation of data. |
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Crosstab |
Data summary in a row-and-column format. |
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RichText |
Paragraphs of text with embedded data columns. |
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OLE |
An OLE object linked or embedded in the DataWindow and associated with the retrieved data. |
For examples of the presentation styles, see the section called “Choosing a presentation style” in Users Guide.
Data sources
The data source specifies where the data in the DataWindow comes from and what data items are displayed. Data can come from tables in a database, a Web service, a file with data that you can import, or code that specifies the data. For databases, the data specification is saved in a SQL statement. In all cases, the DataWindow object saves the names of the data items to display, as well as their datatypes.
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Data source
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Description
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|---|---|
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Quick Select |
The data is coming from one or more tables in a SQL database. The tables must be related through a foreign key. You need to choose only columns, selection criteria, and sorting. |
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SQL Select |
You want more control over the select statement that is generated for the data source. You can specify grouping, computed columns, and so on. |
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Query |
The data has already been selected and the SQL statement is saved in a query object that you have defined in the Query painter. When you define the DataWindow object, the query object is incorporated into the DataWindow and does not need to be present when you run the application. |
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External |
The data is not stored in a database, but is imported from a file (such as a tab-separated or dBASE file) or populated from code. |
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Stored Procedure |
The data is defined in a database stored procedure. |
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Web Service |
The data is defined in a Web service. Support for a Web service data source is not available for the Composite, RichText, and OLE presentation styles. |
Using a DataWindow involves two main steps:
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Use the DataWindow painter to create or edit a DataWindow object.
In the painter, you define the data source, presentation style, and all other properties of the object, such as display formats, validation rules, sorting and filtering criteria, and graphs.
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In your development environment, put a DataWindow control in a window, visual user object, or form or a DataWindow container in a Web page and associate a DataWindow object with the control or container.
It is through the control or container that your application communicates with the DataWindow object you created in the DataWindow painter. You write code to manipulate the DataWindow control or container and the DataWindow object it contains. Typically, your code retrieves and updates data, changes the appearance of the data, handles errors, and shares data between DataWindow controls.
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 the basic application architectures and the requirements for each DataWindow solution.
The basic architectures are:
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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.
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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.
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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.
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.
Features
The PowerBuilder DataWindow control is a container for DataWindow objects in a PowerBuilder application. You can use it in a window to present an interactive display of data. The user can view and change data and send changes to the database.
In addition to the DataWindow control, the DataStore object provides a nonvisual container for server applications and other situations where on-screen viewing is not necessary.
The DataWindow supports data retrieval with retrieval arguments and data update. You can use edit styles, display formats, and validation rules for consistent data entry and display. The DataWindow provides many methods for manipulating the DataWindow, including Modify for changing DataWindow object properties. You can share a result set between several DataWindow controls and you can synchronize data between a client and server.
Development environment
You can develop both parts of your DataWindow implementation in PowerBuilder. You use:
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The DataWindow painter to define DataWindow objects.
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The Window or User Object painters to add DataWindow controls to windows or visual user objects. The DataWindow control is on the drop-down palette of controls for these painters.
In the Window or User Object painters, you can write scripts that control the DataWindow's behavior and manipulate the data it retrieves. Your scripts can also instantiate DataStore objects.
In the PowerBuilder Browser you can examine the properties, events, and methods of DataWindow controls and DataStore objects on the System tab page. If you have a library open that contains DataWindow objects, you can examine the internal properties of the DataWindow object on the Browser's DataWindow tab page.
DataWindow objects
The DataWindow control or DataStore object uses a DataWindow object defined with any presentation style. The DataWindow object determines what data is retrieved and how it is displayed. The control can also display Powersoft reports (PSRs), which do not need to retrieve data.
Database connections
The PowerBuilder DataWindow can use ODBC, JDBC, and native database drivers for database connectivity. Users can connect to a data source on any server to which they have access, including databases and middle-tier servers on the Internet.
To make a connection, you can use the internal Transaction object of the DataWindow, or you can make the connection with a separate PowerBuilder transaction object.
A PowerBuilder application provides a default Transaction object, SQLCA. You can define additional Transaction objects if you need to make additional connections. When you connect with a separate Transaction object, you can control when SQL COMMIT and ROLLBACK statements occur, and you can use the same connection for multiple controls.
For more information about using a Transaction object with a DataWindow, see Using DataWindow Objects.
For more information about PowerBuilder Transaction objects, see the section called “Using Transaction Objects” in Application Techniques.
Coding
You write scripts in the Window or User Object painter to connect to the database, retrieve data, process user input, and update data.
In PowerBuilder, you can take advantage of object inheritance by defining a user object inherited from a DataWindow control and adding your own custom functionality. You can reuse the customized DataWindow control throughout your applications.
You create DataStore objects, the nonvisual version of a DataWindow control, by creating them in a script and calling methods for the object. You can also define a user object that is inherited from a DataStore and customize it. For more information, see Using DataStore Objects.
Libraries and applications
You store DataWindow objects in PowerBuilder libraries (PBLs) during development. When you build your application, you can include the DataWindow objects in the application executable or in PowerBuilder dynamic libraries (PBDs).
For more information about designing DataWindow objects and building a PowerBuilder application, see the section called “Defining DataWindow Objects” in Users Guide and Application Techniques.
