How page request processing works

When processing a 4GL JSP page, the Web Target object model calls events for the psPage object in a specified order. The psPage global object controls the event model and the communication between pages.

Sequence for processing pages

When a browser requests a page, the JSP application server processes a 4GL JSP page in this order:

Starts page processing
- Initializes and restores page variables and parameters
- Creates the server object model
Performs page-specific processing
- Validates the page and binds input data if data is submitted to the current page (typically in preparation for redirection to another page)
- Binds values for EAServer component properties to controls
Generates the new page

The following tables summarize the processing of 4GL JSP pages and show the order in which server-side events are triggered during that processing:

**Table 9-9: Order of events at the start of page processing**
Page processing	Events
Initiate page request	psPage.RequestStart
First page request	psPage.FirstTime
Reload page with data submitted to the reloaded page (typically in preparation for redirection to another page)	psPage.BeforeBinding

**Table 9-10: Order of events that perform page-specific processing**
Page processing	Events
A control had a specified value on request and the value of that control changed	control.Validate
The validation fails	control.ValidationError
The validation succeeds	control.ItemChanged
Data binds to component properties; sets the value of the property of a corresponding EAServer component (for each server object)	none
Validate page	psPage.Validate
The page or any control on the page fails validation	psPage.ValidationError
Binding and validation complete	psPage.AfterBinding
Page control initiates a form submit	psPage.BeforeAction control.ServerAction psPage.AfterAction
For a first request or for pages that require data binding, sets the value of the property of a corresponding EAServer component (for each server object)	none

**Table 9-11: Order of events that generate the new page**
Page processing	Events
If the script does not redirect to another page, process the page template as before. Include other server scripts.	psPage.BeforeGenerate
If the script does not redirect to another page, generation is complete.	psPage.AfterGenerate
Generation is complete. This event is always triggered.	psPage.RequestFinish