Alfresco login with system user and restore back

Many time we need to perform certain operations in alfresco which needs system user access.

Using following code snippet we can use system user and restore back it to normal user authentication.

Note : alfresco 4 Enterprise version considered as of now

try
{
final Authentication authentication = AuthenticationUtil.getFullAuthentication();
AuthenticationUtil.setRunAsUserSystem(); 
// do your operation here
}
finally
{
AuthenticationUtil.clearCurrentSecurityContext();
AuthenticationUtil.setFullAuthentication(authentication);
}