Using HTTP Headers

While you can always just take in HttpContext as an argument to your HTTP endpoint method to read request headers, there's some value in having your endpoint methods be pure functions to maximize the testability of your application code. Since reading header values and parsing those values into specific .NET types is such a common use case, Wolverine has some middleware you can opt into to read the header values and pass them into your endpoint methods using the [Wolverine.Http.FromHeader] attribute as shown from this sample code from the Wolverine testing code:

// As of Wolverine 2.6, you can utilize header data in middleware
public static void Before([FromHeader(Name = "x-day")] string? day)
{
    Debug.WriteLine($"Day header is {day}");
    Day = day; // This is for testing
}

[WolverineGet("/headers/simple")]
public string Get(
    // Find the request header with the supplied name and pass
    // it as the "name" parameter to this method at runtime
    [FromHeader(Name = "x-wolverine")]
    string name)
{
    return name;
}

[WolverineGet("/headers/int")]
public string Get(
    // Find the request header with the supplied name and pass
    // it as the "name" parameter to this method at runtime
    // If the attribute does not exist, Wolverine will pass
    // in the default value for the parameter type, in this case
    // 0
    [FromHeader(Name = "x-wolverine")] int number
)
{
    return (number * 2).ToString();
}

[WolverineGet("/headers/accepts")]
// In this case, push the string value for the "accepts" header
// right into the parameter based on the parameter name
public string GetETag([FromHeader] string accepts)
{
    return accepts;
}

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