Introduction to SharePoint 2013 App Model

Development options in SharePoint 2013

SharePoint Solutions (WSP)

• Same as in SharePoint 2010 & earlier.
• In SharePoint 2013, SharePoint solutions should be mainly used for creating customizations required for administrative functionalities for farm administrators.

Apps

• New in SharePoint 2013
• Apps should be used for creating customizations for end users.

Note – Sandboxed solutions have been deprecated in SharePoint 2013. They are however supported for backward compatibility


What is SharePoint App?

• Stand-alone, self-contained piece of functionality.
• Extends the features and capabilities of a SharePoint site.
• Users can discover/download apps and then install them on their SharePoint site.
• Apps can be uninstalled in an easy & clean manner.
• Apps are available at – 
• Public Store (SharePoint App store)
• Corporate Store (Organization’s App catalog)

SharePoint Solutions Vs. Apps

	SharePoint Solutions	SharePoint Apps
Code Model	Uses Server Object Model	Used Client side object model
Where code resides	Custom code resides on SharePoint server	Custom code resides outside SharePoint server
Where code executes	On the server within SharePoint execution environment	In a completely separate environment (Browser or remote hosting environment)
Code Permissions	Same permissions as SharePoint environment	Limited permissions based on grant.
Deployment effort	More	Less
Recommended use	Customizations for administrative functionality	Customizations for generic functionality
Recommended usage by	Farm administrators	SharePoint end users

Features of SharePoint 2013 Apps

• Can be installed, updated and uninstalled in easy manner.
• As per SharePoint 2013 App model, custom server code will not be placed and executed on SharePoint server/farm. 
• Custom code can be placed & executed at following locations – 
• On client side (Browser)
• On remote server (IIS/Window Azure) which is outside the SharePoint farm.
• Uses following technologies to communicate with SharePoint Server
• Client side object model (CSOM) 
• Rest Services 
• Authentication is done using OAuth.

Hosting options for Apps

• SharePoint hosted apps
• Cloud hosted apps
• Provider hosted
• Auto hosted
• Combination of above

SharePoint hosted apps

• All components of app are hosted on SharePoint farm (on-premise or Office 365).
• App components are hosted in an isolated app domain of SharePoint farm.
• This pattern is easiest to deploy.
• App gets privileges of the signed-in user.
• App can be developed in limited languages viz. HTML + JavaScript.
• No server side code can be used in these types of apps 
• SharePoint components can be accessed via JavaScript (using JSOM library) or REST APIs.

Provider Hosted Apps

• App components are hosted outside SharePoint farm on any other web server/hosting service.
• App gets authorized using OAuth or JavaScript cross domain library.
• App can be developed in any language that is supported by outside web server/hosting service.
• To interact with SharePoint followings options are available for app components - 
• SharePoint client object model
• JavaScript cross domain library
• SP 2013 REST/OData based web service

Auto hosted apps

• These are cloud hosted apps.
• App components are provisioned and deployed on Windows Azure & SQL Azure.
• App gets authorized using OAuth or JavaScript cross domain library.
• App can be developed in any language that is supported by Windows Azure.

Hosting options - Comparison

	SharePoint hosted Apps	Provider hosted Apps	Auto hosted Apps
App component hosting location	Isolated app domain of SharePoint farm	Any web server or hosting service	Windows azure & SQL azure
App authorization	Privileges of the signed in user	•       OAuth •       JavaScript cross domain library	•       OAuth •       JavaScript cross domain library
Supported Languages	HTML + JavaScript	Any language supported by web server/hosting service	Any language supported by Windows Azure web sites
Advantages	•       Reusability of SharePoint items like lists, WebParts etc. •       Easy to create and deploy	•       App can be hosted on any Microsoft/non-Microsoft hosting platform •       Supports many languages	•       Resource provisioning, load balancing & other maintenance tasks are handled by Windows & SQL Azure infrastructure itself.
Disadvantages	•       No server side code allowed. •       App only has authorization of signed-in user	•       Remote components installation, upgrade and uninstallation is headache of developer.	•       Only one hosting option available i.e. Windows & SQL Azure.
Good for	•       Small apps •       Lower complexity apps	•       Enterprise level apps	•       Enterprise level apps

Authentication options in Apps

• Authentication mechanism is dependent on where the app is hosted.
• For SharePoint hosted apps, authentication is handled by SharePoint itself.
• For Cloud hosted apps, following authentication option are available - 
• Client side code along with cross site directory
• Server side code along with OAuth.

App packaging and distribution

• Apps are distributed as ‘App packages’.
• App package may contain different components based on hosting option of App.
• App Package installation Location –         

Hosting Type	Installation Location
SharePoint hosted app	SharePoint server
Provider hosted app	Remote server
Auto hosted app	Windows Azure cloud (Office 365)

App Licensing

• An app license is a digital set of verifiable information stating usage rights of an app.
• Usage right means – 
• App is free or need to be purchased
• App is available on per-user or site basis
• App is a trial or full version
• App license can be verified by querying Office store.

App permission management

• Manage the ability of apps to 
• Access and use internal SharePoint 2013 resources.
• Perform tasks on behalf of users.
• Determining minimum permission levels required for an app 
• Read Only, Write, Manage or Full Control
• Determining app authorization policy 
• User & App Policy, App only Policy, User only policy
• Determining app permission scopes
• Site, Web, List etc.

Tools for developing SharePoint apps

• Visual Studio 2012/13
• For all types of SharePoint Apps
• Napa (Office 365 development tool)
• Can be used only for developing SharePoint hosted apps
• Visual Studio LightSwitch
• Can be used for both SharePoint hosted and Cloud hosted apps

How SharePoint 2013 App model changes customization methodology 

• Apps should be developed for all customizations which are targeted towards end users.
• SharePoint solutions should be developed only for administrative functionalities.
• Sandboxed solutions should not be developed in SharePoint 2013. 
• App development methodology will be dependent on your hosting option. 
• Hosting option of 'Provider hosted apps' will be most suitable for enterprise level applications.