如何使用 ASP.NET Core 依赖注入将 HttpMessageHandler 注入到 HttpClient 对象中？

Question

不使用 ASP.NET Core 的 DI，您可以使用其构造函数将包含 cookie 容器的 ClientHandler 放入 HttpClient 对象中，类似于以下内容：

        var cookieContainer = new CookieContainer();
        var handler = new HttpClientHandler() { CookieContainer = cookieContainer };

        var client = new HttpClient(handler)
            {
                BaseAddress = new Uri(uri),
                Timeout = TimeSpan.FromMinutes(5)
            };

但是当你尝试使用 DI 时，你没有机会调用 HttpClient 的构造函数并将处理程序传入。我尝试了下一行代码：

        services.AddHttpClient<HttpClient>(client =>
            {
                client.BaseAddress = new Uri(uri);
                client.Timeout = TimeSpan.FromSeconds(5);
            });

但实际上，当您获取实例时，它没有 cookie 容器。

Answer 1

您可以通过添加命名客户端（具有其他配置选项）来实现此目的。我们将简单地创建一个带有 cookie 容器的新 HttpClientHandler：

services.AddHttpClient("myServiceClient")
    .ConfigureHttpClient(client =>
    {
        client.BaseAddress = new Uri(uri);
        client.Timeout = TimeSpan.FromSeconds(5);
    })
    .ConfigurePrimaryHttpMessageHandler(
        () => new HttpClientHandler() { CookieContainer = new CookieContainer() }
    );

然后你可以像这样解析客户端：

public class MyService(IHttpClientFactory clientFactory)
{
    // "myServiceClient" should probably be replaced in both places with a 
    // constant (const) string value to avoid magic strings
    var httpClient = clientFactory.CreateClient("myServiceClient");
}

还可以通过向AddHttpClient 提供通用参数来将HttpClient 绑定到服务：

services.AddHttpClient<MyService>("myServiceClient") // or services.AddHttpClient<MyServiceInterface, MyServiceImplementation>("myServiceClient")
    .ConfigureHttpClient(client =>
    {
        client.BaseAddress = new Uri(uri);
        client.Timeout = TimeSpan.FromSeconds(5);
    })
    .ConfigurePrimaryHttpMessageHandler(
        () => new HttpClientHandler() { CookieContainer = new CookieContainer() }
    );

然后您可以在您的服务中简单地接受HttpClient：

public class MyService
{
    public MyService(HttpClient httpClient)
    {
    }
}