How to cache the authentication token

This article demonstrates how to cache the authentication token in order to improve the performance of your application.

Using ASP.NET

Import the Microsoft.Identity.Client NuGet package, which is used to acquire a token. For details, see Install Identity Client NuGet package.

Create a confidential client application property.

private IConfidentialClientApplication _confidentialClientApplication;
private IConfidentialClientApplication ConfidentialClientApplication
{
    get {
        if (_confidentialClientApplication == null) {
            _confidentialClientApplication = ConfidentialClientApplicationBuilder.Create(ClientId)
            .WithClientSecret(ClientSecret)
            .WithAuthority($"https://login.windows.net/{TenantId}")
            .Build();
        }

        return _confidentialClientApplication;
    }
}

Next, use the following code to acquire an AuthenticationResult, using the authentication values you got when you created the Immersive Reader resource.

public async Task<string> GetTokenAsync()
{
    const string resource = "https://cognitiveservices.azure.com/";

    var authResult = await ConfidentialClientApplication.AcquireTokenForClient(
        new[] { $"{resource}/.default" })
        .ExecuteAsync()
        .ConfigureAwait(false);

    return authResult.AccessToken;
}

The AuthenticationResult object has an AccessToken property, which is the actual token you use when launching the Immersive Reader using the SDK. It also has an ExpiresOn property that denotes when the token expires. Before launching the Immersive Reader, you can check whether the token is expired, and acquire a new token only if it expired.

Using Node.JS

Add the request npm package to your project. Use the following code to acquire a token, using the authentication values you got when you created the Immersive Reader resource.

router.get('/token', function(req, res) {
    request.post(
        {
            headers: { 'content-type': 'application/x-www-form-urlencoded' },
            url: `https://login.windows.net/${TENANT_ID}/oauth2/token`,
            form: {
                grant_type: 'client_credentials',
                client_id: CLIENT_ID,
                client_secret: CLIENT_SECRET,
                resource: 'https://cognitiveservices.azure.com/'
            }
        },
        function(err, resp, json) {
            const result = JSON.parse(json);
            return res.send({
                access_token: result.access_token,
                expires_on: result.expires_on
            });
        }
    );
});

The expires_on property is the date and time at which the token expires, expressed as the number of seconds since January 1, 1970 UTC. Use this value to determine whether your token is expired before attempting to acquire a new one.

async function getToken() {
    if (Date.now() / 1000 > CREDENTIALS.expires_on) {
        CREDENTIALS = await refreshCredentials();
    }
    return CREDENTIALS.access_token;
}

Next step