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HOW TO: Pass Custom Headers When Using the JavaScript DocumentViewer
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Tuesday, January 8, 2019 4:01:21 PM(UTC)
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If you're using the DocumentViewer within your company's application, you may wish to add HTTP authorization for downloading internal documents. Below are the few steps you'll need to get started.
Step 1: Provide the header within the clientOur JavaScript SDK allows the developer to customize the requests made to the Documents Service in any way they'd like. You'll simply need to hook into the
DocumentFactory.prepareAjax event. Below are the code snippets from the full sample project, which showcases how to add the basic authorization header:
Code:
// Setup the prepareAjax event
lt.Document.DocumentFactory.prepareAjax.add(prepareAjaxCallback);
// Callback definition
function prepareAjaxCallback(sender, args) {
// Only modify the loadFromUri method
if (args.sourceClass.toLowerCase() != "documentfactory" ||
args.sourceMethod.toLowerCase() != "loadfromuri")
return;
// Ensure the headers object exists
if (!args.settings.headers)
args.settings.headers = {};
// Add the authorization header
var myUsername = "username";
var myPassword = "password";
args.settings.headers["Authorization"] = "Basic " + btoa(myUsername + ":" + myPassword);
}
Note: A request made by the DocumentViewer for loading an image does not fire this event by default. To fire the prepareAjax event for requests made to the service, simply set the
DocumentViewer.useAjaxImageLoading property to true.
Below is a download link for the complete client-side demo for this:
Step 2: Pass-through the header within the Documents ServiceBy default, our Documents Service uses a blank
WebClient for the LoadFromUri requests. However, you can provide a custom one by modifying the
LoadDocumentOptions object used within the FactoryController.cs file:
Project Location: LEADTOOLS 20\Examples\JS\Documents\DocumentViewer\Services\DocumentsService
File Location: Controllers\FactoryController.cs
Line Number: 101 - 105
Code:
var loadOptions = new LoadDocumentOptions();
loadOptions.Cache = cache;
loadOptions.UseCache = cache != null;
loadOptions.CachePolicy = ServiceHelper.CreatePolicy();
// EDIT: Updated WebClient
loadOptions.WebClient = new WebClient();
// Pass-through various headers
string[] passthroughHeaders = new string[] { "Authorization" };
foreach (string header in passthroughHeaders)
if (Request.Headers.Contains(header))
if (Request.Headers.TryGetValues(header, out IEnumerable<string> values))
foreach (string value in values)
loadOptions.WebClient.Headers.Add(header, value);
else
loadOptions.WebClient.Headers.Add(header);
As you can see from the
passthroughHeaders variable in the snippet above, this can be easily extended to pass any header you'd like.
Optional step 3: Testing the authorization headerBy default, this authorization header is not required. Below is the modification I made to the Documents Service for testing purposes.
Project Location: LEADTOOLS 20\Examples\JS\Documents\DocumentViewer\Services\DocumentsService
File Location: Controllers\TestController.cs
Line Number: 28
Code:
// EDIT: Added test endpoint
[HttpGet]
public HttpResponseMessage AuthorizedImage()
{
// Configure expected username/password
string expectedUsername = "username";
string expectedPassword = "password";
// Validate authentication header
HttpResponseMessage response = new HttpResponseMessage
{
Content = new StringContent("Unknown error"),
StatusCode = HttpStatusCode.InternalServerError
};
try
{
// Ensure header is present
var authHeader = Request.Headers.Authorization;
if (authHeader == null)
throw new NullReferenceException("No authorization header present");
// Validate scheme
if (!authHeader.Scheme.Equals("basic", StringComparison.CurrentCultureIgnoreCase))
throw new ArgumentException("Not using basic authorization");
// Validate parameter
string decoded = System.Text.Encoding.Default.GetString(
Convert.FromBase64String(authHeader.Parameter)
);
var match = new System.Text.RegularExpressions.Regex("^([^:]*):(.*)$").Match(decoded);
if (match == null || !match.Success)
throw new ArgumentException("Parameter not formatted properly");
// Validate some username and password
if (!match.Groups[1].Value.Equals(expectedUsername))
throw new ArgumentException("Invalid username");
if (!match.Groups[2].Value.Equals(expectedPassword))
throw new ArgumentException("Invalid password");
}
catch (Exception ex)
{
response.Content = new StringContent(
$"Authorization header not configured properly: {ex.Message}"
);
response.StatusCode = HttpStatusCode.Unauthorized;
return response;
}
// Validated successfully
response.StatusCode = HttpStatusCode.OK;
// Populate with data
response.Content = new ByteArrayContent(
System.IO.File.ReadAllBytes(@"C:\Users\Public\Documents\LEADTOOLS Images\cannon.jpg")
);
return response;
}
Anthony Northrup
Developer Support Engineer
LEAD Technologies, Inc.
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HOW TO: Pass Custom Headers When Using the JavaScript DocumentViewer
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