A get request is an initial
request for a page either made when a user enters an URL or when a
link or button is clicked that takes the user to a new page. The following diagram shows how a Visualforce page interacts with a controller extension or a custom controller
class during a get request:
In the diagram above the user initially requests a page, either
by entering a URL or clicking a link or button. This initial page
request is called the
get request.
- The constructor methods on the associated custom controller or
controller extension classes are called, instantiating the controller
objects.
- If the page contains any custom components, they are created and
the constructor methods on any associated custom controllers or controller
extensions are executed. If attributes are set on the custom component
using expressions, the expressions are evaluated after the constructors
are evaluated.
- The page then executes any assignTo attributes on any custom components on the page. After the assignTo methods are executed, expressions
are evaluated, the action attribute on the <apex:page> component is evaluated, and all other method calls, such as getting
or setting a property value, are made.
- If the page contains an <apex:form> component, all of the information necessary to maintain the state
of the database between page requests is saved as an encrypted view state. The view state is updated whenever the page is
updated.
- The resulting HTML is sent to the browser. If there are any client-side
technologies on the page, such as JavaScript, the browser executes
them.
As the user interacts with the page, the page contacts the controller
objects as required to execute action, getter, and setter methods.
Once a new get request is made by the user, the view state and
controller objects are deleted.
If the user interaction requires a page update, such as when the
user clicks a Save button that triggers a save
action, a postback request is made. For more information
on postback requests, see Order of Execution for Visualforce Page Postback Requests.
For a specific example of a get request, see Examples of Visualforce Page Execution Order.