How the Web DataWindow works – PB Docs 126

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 HTMLGenerator126 component
that is preinstalled in EAServer 6.x.
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 .

note.png Disabling instance pooling when deploying Web DataWindow

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 HTMLGenerator126
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 by setting the
property to false in the HTMLGenerator126.props file in the EAServerRepositoryComponentDataWindow directory.
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.

Figure 6-1: How the Web DataWindow works


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:

  1. In a Web browser, a user requests the URL for a page.

  2. 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.

  3. The server-side scripts connect to the (transaction)
    server component, passing it information about the DataWindow and
    database connection.

  4. 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.

  5. The server component returns the JavaScript and
    XHTML or HTML and to the page server.

  6. 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

  7. The user interacts with the DataWindow—for
    example, requesting the next page or updating the data.

  8. The Web server passes the URL with added action
    parameters to the page server, and the cycle begins again.

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