Data Access in SharePoint And Remote App :Inbound and Outbound scenarios

1)Data Access in SharePoint And Remote App :Inbound scenarios

Inbound data connectivity

The following connectivity options are available for inbound scenarios:

• OAuth: An open protocol that enables secure authorization in a simple and standard way.
  AppOnly Policy : enables users to approve an application to act on their behalf without sharing their user name and password.                                                                                                         
  Server Side Code :You can use OAuth with server-side code. It is a good option if you need to run a non-interactive process, or if you need to elevate privileges to other than those of the logged-on user. For information about OAuth, see Authorization and authentication for apps in SharePoint 2013.
• Cross-domain library: A client-side alternative in the form of a JavaScript file (SP.RequestExecutor.js) hosted in the SharePoint website that you can reference in your remote app as long as they are in the same internet zone. Multi-domain Interaction : The cross-domain library allows you to interact with more than one domain in your remote app page through a proxy.                                                                        
  Client Side Code : This is a good option if you prefer your app code to run in the client rather than in the server, or if there are connectivity barriers, such as firewalls, between SharePoint and your remote infrastructure. For more information, see How to: Access SharePoint 2013 data from remote apps using the cross-domain library.
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2)Data Access in SharePoint And Remote App :Outbound scenarios

Outbound data connectivity

The following connectivity options are available for outbound scenarios (see Figure 2):

• Web proxy: As a developer, you can use the web proxy exposed in client APIs such as the JavaScript/.NET client object models. When you use the web proxy, you issue the initial request to SharePoint. In turn, SharePoint requests the data to the specified endpoint and forwards the response back to your page. Use the web proxy when you want the communication to occur at the server level
  Both Javascript/.Net CSOM is available.                                                                               
  Direct calls through browser are not supported.
  For more information, see How to: Query a remote service using the web proxy in SharePoint 2013.
• Remote event receivers: You can use remote event receivers to handle events that occur to an item in the app, such as a list, a list item, or a web. These events resemble those in a traditional SharePoint solution, except that they can work with the remote components of the app for SharePoint.
  Only .Net CSOM is available.    
  Client Side Technologies are not supported .                                                                 
  App can not access resource as current logged in User .
   For more information, seeHandling events in apps for SharePoint.

•  Custom proxy page for the cross-domain library: You can use the cross-domain library to access data in your remote app if you provide a custom proxy page that is hosted in the remote app infrastructure. As the developer, you are responsible for the custom proxy page implementation and must deal custom logic, such as the authentication mechanism, to the remote app. Use the cross-domain library with a custom proxy page if you want the communication to occur at the client level. 

  Can not add SharePoint Components to Remote App                                                         
  .Net CSOM is not available
  

  For more information, see How to: Create a custom proxy page for the cross-domain library in SharePoint 2013.

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