Apex Classes used in Visualforce Controllers

StandardController Class  Vs StandardSetController Class

StandardController Class:

• StandardController objects reference the pre-built visualforce controllers provided by salesforce.com
• Only time it is necessary to refer standardcontroller object when defining the extension for standardcontroller.
• Apexpages.standardcontroller sc=new ApexPages.StandardController(sobject);

StandardSetController Class:

• StandardSetController objects allows to create list controllers similar to or extensions of the pre-built visualforce list controllers provided by salesforce.com.It also contains prototype object.
• Prototype object is single sobject contained within the visuforce standardsetcontroller class.
• If prototype object fields are set ,those values are used save action.

For List of Sobjects:

List<account> ls=[select id,name from account limit 5];

ApexPages.StandardSetController ssc=new ApexPages.StandardSetController(ls);

For QueryLocator:

ApexPages.StandardSetController ssc=new ApexPages.StandardSetController(Database.getQueryLocator([Select id,name from Account Limit 5]));

Action Class:

• Use ApexPages.Action class to create an action method that you can use in visualforce controller or extension controller.
• ApexPages.Action saveaction=new ApexPages.Action('{!save}');

Message Class:

• When using Standard Controller,all validation errors,both  standard and custom that occur when end user saves the page are automatically added to the page error collection.
• If you use Custom Controller or extension,you must use the message class to collecting errors.
• ApexPages.message mss=new ApexPages.message(ApexPages.Severity,summary);

PageReference Class:

• PageReference is a reference to instantiation of a page.
• PageReference consists of URL and a set of query parameter  names,values.
• By using PageReference Object,To view or set the query string parameters and values of page.
• Also used ,to navigate the user to different page as  the result of an action method.