How to override Jomsocial Controller

If you already override jomsocial template files then don't think that in same way you can override controller as well.
Before talking about how to override Jomsocial Controller, lets see why we need to override controller. If you hack the core files directly & made changes as you want. After some day when you upgrade jomsocial then those changes from the hacked files will be removed & then again you have to hack the core files. So this is very tedious task to check which file & what code you have hacked. Solution on hacking is obviously you have to override controller.

To override jomsocial controller you need a plugin which will override controller. In this plugin we just replace default controller object with our own custom class.
Before the system controller is created. Plugin may override the controller class name.
Plugin should contain following code.

<?php
defined( '_JEXEC' ) or die( 'Restricted access' );
jimport( 'joomla.plugin.plugin' );
require_once( JPATH_SITE .'/components/com_community/libraries/core.php');
require_once( JPATH_SITE .'/components/com_community/controllers/mybulletin.php');

class plgCommunityMybulletin extends CApplications
{

function plgCommunityMybulletin(& $subject, $config){
parent::__construct($subject, $config);
}

function onBeforeControllerCreate( &$controllerClassName )
{
$view = JRequest::getVar('view');
if($view == 'groups') {
$controllerClassName = 'MybulletinController'; // MybulletinController is class name which extends in your controller
return true;
}
return false;
}

}

Lets see the how to create controller.
If you wanna override groups controller then copy that file & paste it in the same folder(com_community/controller). Rename that file with what you have mentioned in plugin($controllerClassName value). In this case i rename that file with mybulletin.php & do changes as you want. Just make sure that you have added following line at the top of the file.
jimport ('joomla.application.component.controller');
require_once (COMMUNITY_COM_PATH.DS.'controllers'.DS.'controller.php');
To off email on bulletin creation i did override jomsocial group controller. You can find plugin & controller files here & make changes as you want.