Create a custom proxy page for the cross-domain library in SharePoint 2013

SharePoint Add-ins

Learn how to create a custom proxy page to access data in a remote service from a SharePoint webpage by using the cross domain library in SharePoint.

Last modified: September 17, 2015

Applies to: apps for SharePoint | Office 365 | SharePoint Add-ins | SharePoint Foundation 2013 | SharePoint Server 2013

Note Note

The name "apps for SharePoint" is changing to "SharePoint Add-ins". During the transition, the documentation and the UI of some SharePoint products and Visual Studio tools might still use the term "apps for SharePoint". For details, see New name for apps for Office and SharePoint.

When you are building SharePoint Add-ins, you usually have to incorporate data from various sources. However, for security reasons, there are blocking mechanisms that prevent communication with more than one domain at a time.

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

You need a development environment as explained in Get started creating provider-hosted SharePoint Add-ins.

Core concepts to know before using a custom proxy page with SharePoint Add-ins

The following table lists some useful articles that can help you understand the concepts involved in a cross-domain scenario for SharePoint Add-ins.

Table 1. Core concepts for using a custom proxy page

Article title

Description

SharePoint Add-ins

Learn about the new add-in model in SharePoint that enables you to create add-ins, which are small, easy-to-use solutions for end users.

Secure data access and client object models for SharePoint Add-ins

Learn about data access options in SharePoint Add-ins. This topic provides guidance on the high-level alternatives you have to choose from when working with data in your add-in.

Host webs, add-in webs, and SharePoint components in SharePoint 2013

Learn about the difference between host webs and add-in webs. Find out which SharePoint components can be included in a SharePoint Add-in, which components are deployed to the host web, which components are deployed to the add-in web, and how the add-in web is deployed in an isolated domain.

Client-side Cross-domain Security

Explore cross-domain threats and use cases, and security principles for cross-origin requests, and weigh the risks for developers to enhance cross-domain access from web applications that run in the browser.

To read data from the remote service, you must do the following:

  1. Create a SharePoint Add-in project.

  2. Modify the add-in manifest to allow communication from the remote add-in.

  3. Create the custom proxy page and a content page in the web project.

  4. Create a page that uses the cross-domain library in the SharePoint Add-in project.

To create the SharePoint Add-in project

  1. Open Visual Studio as administrator. (To do this, right-click the Visual Studio icon on the Start menu, and choose Run as administrator.)

  2. Create the provider-hosted SharePoint Add-in as explained in Get started creating provider-hosted SharePoint Add-ins and name it ProxyPageApp.

To edit the add-in manifest file

  1. In Solution Explorer, right-click the AppManifest.xml file, and choose View code.

  2. Replace the entire AppPrincipal element with the following.

    <AppPrincipal>
        <Internal AllowedRemoteHostUrl="~remoteAppUrl"/>
    </AppPrincipal>
    
    NoteNote

    The AllowedRemoteHostUrl attribute is used to specify the remote domain. The ~remoteAppUrl resolves to the remote add-in URL. For more information about tokens, see Explore the app manifest structure and the package of a SharePoint Add-in.

To create a custom proxy page

  1. After the Visual Studio solution has been created, right-click the web application project (not the SharePoint Add-in project) and add a new Web Form by choosing Add > New Item > Web > Web Form. Name the form Proxy.aspx.

  2. In the Proxy.aspx file, replace the entire html element and it's children with the following HTML code. Leave all the markup above the html element as it is. The HTML code contains markup and JavaScript that performs the following tasks:

    • Provides a placeholder for the cross-domain library JavaScript file.

    • Extracts the add-in web URL from the referrer.

    • Dynamically loads the cross-domain library JavaScript file into the placeholder.

    • Provides settings for the RequestExecutorMessageProcessor object.

    • Initializes the RequestExecutorMessageProcessor object.

    <html xmlns="http://www.w3.org/1999/xhtml">
    <head runat="server">
        <meta http-equiv="X-UA-Compatible" content="IE=8" /> 
        <title>Custom Proxy Host Page</title>
        <script 
            src="http://ajax.aspnetcdn.com/ajax/4.0/1/MicrosoftAjax.js" 
            type="text/javascript">
        </script>
        <script 
            type="text/javascript" 
            src="http://ajax.aspnetcdn.com/ajax/jQuery/jquery-1.7.2.min.js">
        </script>
    
        <!-- Script to load the cross-domain library js file -->
        <script type="text/javascript">
            var hostweburl;
    
            $(document).ready(function(){
                //Get the URI decoded host web URL.
                hostweburl =
                    decodeURIComponent(
                        getQueryStringParameter("SPHostUrl")
                );
    
                // The cross-domain js file is in a URL in the form:
                // host_web_url/_layouts/15/SP.RequestExecutor.js
                var scriptbase = hostweburl + "/_layouts/15/";
    
                // Load the js file 
                $.getScript(scriptbase + "SP.RequestExecutor.js", initCustomProxy);
            });
    
            //Function to initialize the custom proxy page
            //  must set the appropriate settings and implement
            //  proper authentication mechanism
            function initCustomProxy() {
                var settings =
                {
                    originAuthorityValidator: function (messageOriginAuthority) {
                        // This page must implement the authentication for the
                        //   remote add-in.
                           // You should validate if messageOriginAuthority is
                           //  an approved domain to receive calls from.
                        return true;
                    }
                };
                SP.RequestExecutorMessageProcessor.init(settings);
            }
    
            // Function to retrieve a query string value.
            // For production purposes you may want to use
            //  a library to handle the query string.
            function getQueryStringParameter(paramToRetrieve) {
                var params =
                    document.URL.split("?")[1].split("&");
                var strParams = "";
                for (var i = 0; i < params.length; i = i + 1) {
                    var singleParam = params[i].split("=");
                    if (singleParam[0] == paramToRetrieve)
                        return singleParam[1];
                }
            }
        </script>
    </head>
    <body>
        
    </body>
    </html>
    
    
    
    Important noteImportant

    In a production SharePoint Add-in, you must provide the authorization logic and return the appropriate value in the originAuthorityValidator object in settings.

To create a content page

  1. Right-click the web application project in Solution Explorer and add a new Web Form by choosing Add > New Item > Web > Web Form. Name the form Content.aspx..

  2. Copy the following code and paste it in the Page_Load method in the code-behind file. The code performs the following tasks:

    • Sets the output content-type to text/plain.

    • Writes the content to the output buffer.

    • Ends the connection.

    string content;
    content = "Just some text.";
    Response.ContentType="text/plain";
    Response.Write(content);
    Response.End();
    
    

To create a SharePoint webpage that uses the cross-domain library

  1. Right-click the SharePoint Add-in project, and choose Add > New Item > Office/SharePoint > Module.

  2. Name the module Pages, and then choose Add.

  3. Right-click the Pages folder and choose Add > New Item> Office/SharePoint > Page.

  4. Name the page Home.aspx and then choose Add.

  5. Open the Home.aspx page if it isn't opened automatically.

  6. Copy the following code and paste it in the PlaceHolderMain content tag.

    <!-- The page dynamically loads the cross-domain library's
        js file, rescript acts as the placeholder. -->
    <script 
        type="text/javascript"
        id="rescript"
        src="../_layouts/15/SP.RequestExecutor.js">
    </script>
        Data from the remote domain: <span id="TextData"></span>
    
        <!-- Main script to retrieve the host web's title -->
        <script type="text/javascript">
        (function () {
            var executor;
            var hostweburl;
            var remotedomain;
    
            remotedomain = "<your_remote_add-in_domain>";
    
            //Get the URI decoded host web URL.
            hostweburl =
                decodeURIComponent(
                    getQueryStringParameter("SPHostUrl")
            );
    
            // Initialize the RequestExecutor with the custom proxy URL.
            executor = new SP.RequestExecutor(remotedomain);
            executor.iFrameSourceUrl = "Proxy.aspx?SPHostUrl=" + hostweburl;
    
            // Issue the call against the remote endpoint.
            // The response formats the data in plain text.
            // The functions successHandler and errorHandler attend the
            //      sucess and error events respectively.
            executor.executeAsync(
                {
                    url:
                        remotedomain + "Content.aspx",
                    method: "GET",
                    headers: { "Accept": "text/plain" },
                    success: successHandler,
                    error: errorHandler
                }
            );
        })();
    
        // Function to handle the success event.
        // Prints the data to the placeholder.
        function successHandler(data) {
            document.getElementById("TextData").innerText =
                data.body;
        }
    
        // Function to handle the error event.
        // Prints the error message to the page.
        function errorHandler(data, errorCode, errorMessage) {
            document.getElementById("TextData").innerText =
                "Could not complete cross-domain call: " + errorMessage;
        }
    
        // Function to retrieve a query string value.
        // For production purposes you may want to use
        //  a library to handle the query string.
        function getQueryStringParameter(paramToRetrieve) {
            var params =
                document.URL.split("?")[1].split("&");
            var strParams = "";
            for (var i = 0; i < params.length; i = i + 1) {
                var singleParam = params[i].split("=");
                if (singleParam[0] == paramToRetrieve)
                    return singleParam[1];
            }
        }
        </script>
    
    
  7. In the preceding code that you pasted, find the line remotedomain = "<your_remote_add-in_domain>";, and replace the placeholder <your_remote_add-in_domain> with the "localhost" URL that your web application uses when you are running the add-in with F5 in Visual Studio. To find this value, select the web application project in Solution Explorer. The URL property will be in the Properties pane. Use the entire value, including the protocol, the port, and the closing slash; for example "http://localhost:45072".

  8. Save and close the file.

  9. Open the appmanifest.xml file, and set the Start page value to ProxyPageApp/Pages/Home.aspx.

To build and run the solution

  1. Make sure that the SharePoint Add-in project is set as the startup project.

  2. Press the F5 key.

    Note Note

    When you press F5, Visual Studio builds the solution, deploys the add-in, and opens the permissions page for the add-in.

  3. Choose the Trust It button.

    The Home page will open and it should look like the following. It may take a few seconds for the phrase "Just some text" to appear because it is being fetched from the remote domain's Content.aspx page.

    Data from the remote service in a SharePoint webpage

    SharePoint page with data from a remote service
Table 2. Troubleshooting the solution

Problem

Solution

Visual Studio does not open the browser after you press the F5 key.

Set the SharePoint Add-in project as the startup project.

Unhandled exception SP is undefined.

Make sure that you can access the SP.RequestExecutor.js file in a browser window.

This article demonstrated how to access remote data by using a custom proxy page for the cross-domain library in SharePoint. As a next step, you can learn about other data access options available in SharePoint Add-ins. To learn more, see the following:

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