Adapters

Adapters define a script interface to your server application. They allow you to insert scripting languages into a page and retrieve information by making calls from your script code to the adapters. For example, you can use an adapter to define data fields to be displayed on an HTML page. A scripted HTML page can then contain HTML content and script statements that retrieve the values of those data fields. This is similar to the transparent tags used in Web Broker applications. Adapters also support actions that execute commands. For example, clicking on a hyperlink or submitting an HTML form can initiate adapter actions.

Adapters simplify the task of creating HTML pages dynamically. By using adapters in your application, you can include object-oriented script that supports conditional logic and looping. Without adapters and server-side scripting, you must write more of your HTML generation logic in event handlers. Using adapters can significantly reduce development time.

See Server-side scripting in WebSnap for more details about scripting.

Four types of adapter components can be used to create page content: fields, actions, errors and records.

Fields

Fields are components that the page producer uses to retrieve data from your application and to display the content on a Web page. Fields can also be used to retrieve an image. In this case, the field returns the address of the image written to the Web page. When a page displays its content, a request is sent to the Web server application, which invokes the adapter dispatcher to retrieve the actual image from the field component.

Actions

Actions are components that execute commands on behalf of the adapter. When a page producer generates its page, the scripting language calls adapter action components to return the name of the action along with any parameters necessary to execute the command. For example, consider clicking a button on an HTML form to delete a row from a table. This returns, in the HTTP request, the action name associated with the button and a parameter indicating the row number. The adapter dispatcher locates the named action component and passes the row number as a parameter to the action.

Errors

Adapters keep a list of errors that occur while executing an action. Page producers can access this list of errors and display them in the Web page that the application returns to the end user.

Records

Some adapter components, such as TDataSetAdapter, represent multiple records. The adapter provides a scripting interface which allows iteration through the records. Some adapters support paging and iterate only through the records on the current page.