Visualforce Developer Guide

Introducing Visualforce
Tools for Visualforce Development
Getting a Quick Start with Visualforce
Customizing the Appearance and Output of Visualforce Pages
Standard Controllers
Standard List Controllers
Custom Controllers and Controller Extensions
What are Custom Controllers and Controller Extensions?
Building a Custom Controller
Building a Controller Extension
Building a Custom List Controller
Controller Methods
Controller Class Security
Working with Large Sets of Data
Considerations for Creating Custom Controllers and Controller Extensions
Order of Execution in a Visualforce Page
Testing Custom Controllers and Controller Extensions
Validation Rules and Custom Controllers
Using the transient Keyword
Advanced Examples
Overriding Buttons, Links, and Tabs with Visualforce
Using Static Resources
Creating and Using Custom Components
Dynamic Visualforce Bindings
Dynamic Visualforce Components
Integrating Email with Visualforce
Visualforce Charting
Creating Maps with Visualforce
Render Flows with Visualforce
Templating with Visualforce
Developing for Mobile Devices
Adding Visualforce to a Force.com AppExchange App
Using JavaScript in Visualforce Pages
Best Practices
Standard Component Reference
Appendices
Glossary
PDF

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Building a Controller Extension

A controller extension is any Apex class containing a constructor that takes a single argument of type ApexPages.StandardController or CustomControllerName, where CustomControllerName is the name of a custom controller you want to extend.

The following class is a simple example of a controller extension:

The following Visualforce markup shows how the controller extension from above can be used in a page:

The extension is associated with the page using the extensions attribute of the <apex:page> component.

As with all controller methods, controller extension methods can be referenced with {! } notation in page markup. In the example above, the {!greeting} expression at the top of the page references the controller extension's getGreeting method.

Because this extension works in conjunction with the Account standard controller, the standard controller methods are also available. For example, the value attribute in the <apex:inputField> tag retrieves the name of the account using standard controller functionality. Likewise, the <apex:commandButton> tag references the standard account save method with its action attribute.

Multiple controller extensions can be defined for a single page through a comma-separated list. This allows for overrides of methods with the same name. For example, if the following page exists:
with the following extensions:
The value of the <apex:outputText> component renders as foo-One. Overrides are defined by whichever methods are defined in the “leftmost” extension, or, the extension that is first in the comma-separated list. Thus, the getFoo method of ExtOne is overriding the method of ExtTwo.

Like other Apex classes, controller extensions run in system mode. Consequently, the current user's credentials are not used to execute controller logic, and the user's permissions and field-level security do not apply. However, if a controller extension extends a standard controller, the logic from the standard controller does not execute in system mode. Instead, it executes in user mode, in which the permissions, field-level security, and sharing rules of the current user apply.

You can choose whether a controller extension respects a user's organization-wide defaults, role hierarchy, and sharing rules by using the with sharing keywords in the class definition. For information, see “Using the with sharing or without sharing Keywords” in the Apex Developer Guide.

Note