HttpRequestTransformer

Contains the following DelegatingHandler implementations:

• HttpRequestPipelineHandler - used to inspect or modify outgoing HTTP requests prior to sending, and/or to inspect or modify received HTTP response messages. An example use case includes a backchannel HTTP client in a server-side app where you need to attach the authorization token for the calling user to an outgoing request.
• GZipCompressor - compresses the content of outgoing HTTP requests using GZip compression.
• BrotliCompressor - compresses the content of outgoing HTTP requests using Brotli compression (.NET Standard 2.1 and later).

In addition, the HttpClientFactory class can be used to simplify creation of HttpClient instances in applications that do not use dependency injection.

Getting Started

Add the Jaahas.HttpRequestTransformer NuGet package to your project.

Example: Adding a Header to Outgoing Requests

In this example, we'll attach a bearer token to outgoing requests made by a backchannel client in an ASP.NET Core application. First, add an HttpRequestPipelineHandler to the request pipeline for your HttpClient:

public void ConfigureServices(IServiceCollection services) {
    services
        .AddHttpClient("Test", options => {
            options.BaseAddress = new Uri("https://some-remote-site.com");
        })
        .AddHttpMessageHandler(() => new Jaahas.Http.HttpRequestPipelineHandler(AddBearerTokenToRequest));
}

Next, implement the function that will retrieve the access token for a given ClaimsPrincipal:

private static Task AddBearerTokenToRequest(HttpRequestMessage request, CancellationToken cancellationToken) {
    var principal = request.GetStateProperty<ClaimsPrincipal>();
    if (principal?.Identity?.IsAuthenticated ?? false) {
        string token;

        // Plug in your own logic here to get the actual token for the principal...

        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
    }
    return Task.CompletedTask;
}

Finally, in your code that will use the client, add a ClaimsPrincipal to the outgoing request's properties prior to sending:

[ApiController]
[Authorize]
public class MyController : ControllerBase {

    private readonly HttpClient _httpClient;


    public MyController(IHttpClientFactory factory) {
        _httpClient = factory.CreateClient("Test");
    }


    public async Task<IActionResult> GetDataFromRemoteSite(CancellationToken cancellationToken) {
        var request = new HttpRequestMessage(HttpMethod.Get, "/api/data").AddStateProperty(User);
        var response = await _httpClient.SendAsync(request, cancellationToken);

        // Process the response and return the result to the caller.
    } 

}

Example: Logging Detailed Response Information

In this example, we'll create an HTTP handler that will write detailed information about an HTTP request and response to the console:

public void ConfigureServices(IServiceCollection services) {
    services
        .AddHttpClient("Test", options => {
            options.BaseAddress = new Uri("https://some-remote-site.com");
        })
        .AddHttpMessageHandler(() => new Jaahas.Http.HttpRequestPipelineHandler(LogResponseDetails));
}


private static Task LogResponseDetails(HttpResponseMessage response, CancellationToken cancellationToken) {
    // Method and endpoint.
    Console.WriteLine($"{response.RequestMessage.Method} {response.RequestMessage.RequestUri}");
    Console.WriteLine();

    // Request headers.
    foreach (var item in response.RequestMessage.Headers) {
        Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
    }
    if (response.RequestMessage.Content != null) {
        foreach (var item in response.RequestMessage.Content.Headers) {
            Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
        }
    }
    Console.WriteLine();

    // Response summary.
    Console.WriteLine($"HTTP/{response.Version.Major}.{response.Version.Minor} {(int) response.StatusCode} {response.ReasonPhrase}");
    Console.WriteLine();

    // Response headers.
    foreach (var item in response.Headers) {
        Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
    }
    if (response.Content != null) {
        foreach (var item in response.Content.Headers) {
            Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
        }
    }

    return Task.CompletedTask;
}

Example: Logging Detailed Response Information with Timing Information

In this example, we extend the previous example to include information about how long an HTTP request took. Rather than specifying a delegate to invoke before sending a request or after receiving a response, we specify a delegate that can invoke the inner handlers in the request pipeline, and then perform additional work once the response has been received:

public void ConfigureServices(IServiceCollection services) {
    services
        .AddHttpClient("Test", options => {
            options.BaseAddress = new Uri("https://some-remote-site.com");
        })
        .AddHttpMessageHandler(() => new Jaahas.Http.HttpRequestPipelineHandler(LogResponseDetailsWithTiming));
}


private static async Task LogResponseDetailsWithTiming(
    HttpRequestMessage request, 
    HttpMessageHandlerDelegate next, 
    CancellationToken cancellationToken
) {
    // Start the stopwatch.
    var stopwatch = System.Diagnostics.Stopwatch.StartNew();

    // Invoke the inner handlers.
    var response = await next(request, cancellationToken).ConfigureAwait(false);

    // Measure the elapsed time.
    var elapsed = stopwatch.ElapsedMilliseconds;

    // Method and endpoint.
    Console.WriteLine($"{response.RequestMessage.Method} {response.RequestMessage.RequestUri}");
    Console.WriteLine();

    // Request headers.
    foreach (var item in response.RequestMessage.Headers) {
        Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
    }
    if (response.RequestMessage.Content != null) {
        foreach (var item in response.RequestMessage.Content.Headers) {
            Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
        }
    }
    Console.WriteLine();

    // Response summary and elapsed time.
    Console.WriteLine($"HTTP/{response.Version.Major}.{response.Version.Minor} {(int) response.StatusCode} {response.ReasonPhrase}");
    Console.WriteLine($"{elapsed} ms");
    Console.WriteLine();

    // Response headers.
    foreach (var item in response.Headers) {
        Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
    }
    if (response.Content != null) {
        foreach (var item in response.Content.Headers) {
            Console.WriteLine($"{item.Key}: {string.Join(", ", item.Value)}");
        }
    }
}

Example: Add GZip Compression to Outgoing HTTP Content

The following example shows how to add GZip compression to all outgoing HTTP requests sent by an HttpClient:

public void ConfigureServices(IServiceCollection services) {
    services
        .AddHttpClient("Test", options => {
            options.BaseAddress = new Uri("https://some-remote-site.com");
        })
        .AddHttpMessageHandler(() => new Jaahas.Http.GZipCompressor());
}

It is also possible to specify a callback that decides on a case-by-case basis if an outgoing request should be compressed:

public void ConfigureServices(IServiceCollection services) {
    services
        .AddHttpClient("Test", options => {
            options.BaseAddress = new Uri("https://some-remote-site.com");
        })
        .AddHttpMessageHandler(() => new Jaahas.Http.GZipCompressor(req => req.RequestUri.LocalPath.Contains("/api/upload")));
}