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[英]How to configure web proxy for HttpClient created directly via HttpClientFactory?
[英]Having dynamic proxy with HttpClientFactory implementation
我有Asp.Net Core WebApi
。 我正在根据HttpClientFactory 模式发出 Http 请求。 这是我的示例代码:
public void ConfigureServices(IServiceCollection services)
{
...
services.AddHttpClient<IMyInterface, MyService>();
...
}
public class MyService: IMyInterface
{
private readonly HttpClient _client;
public MyService(HttpClient client)
{
_client = client;
}
public async Task CallHttpEndpoint()
{
var request = new HttpRequestMessage(HttpMethod.Get, "www.customUrl.com");
var response = await _client.SendAsync(request);
...
}
}
我想通过动态代理实现发送请求。 这基本上意味着我可能需要为每个请求更改代理。 至于现在我发现了 2 个 approuces,其中没有一个对我来说似乎很好:
1.有一个像这样的静态代理:
public void ConfigureServices(IServiceCollection services)
{
...
services.AddHttpClient<IMyInterface, MyService>().ConfigurePrimaryHttpMessageHandler(() =>
{
return new HttpClientHandler
{
Proxy = new WebProxy("http://127.0.0.1:8888"),
UseProxy = true
};
});
...
}
但是在这种方法中,每个服务只能有一个代理。
2.为每个请求处理HttpClient
:
HttpClientHandler handler = new HttpClientHandler()
{
Proxy = new WebProxy("http://127.0.0.1:8888"),
UseProxy = true,
};
using(var client = new HttpClient(handler))
{
var request = new HttpRequestMessage(HttpMethod.Get, "www.customUrl.com");
var response = await client.SendAsync(request);
...
}
但是这样我违反了 HttpClientFactory 模式,它可能会导致应用程序性能出现问题,如下 文所述
有没有第三种方法可以在不重新创建HttpClient
情况下动态更改代理?
在实例化后,无法更改HttpClientHandler
的任何属性或将新版本的HttpClientHandler
分配给现有的HttpClient
。 因此,不可能为特定的HttpClient
设置动态代理:您只能指定一个代理。
实现此目的的正确方法是使用命名客户端,并为每个代理端点定义一个客户端。 然后,您需要注入IHttpClientFactory
并选择要使用的代理之一,请求实现该代理的命名客户端。
services.AddHttpClient("MyServiceProxy1").ConfigurePrimaryHttpMessageHandler(() =>
{
return new HttpClientHandler
{
Proxy = new WebProxy("http://127.0.0.1:8888"),
UseProxy = true
};
});
services.AddHttpClient("MyServiceProxy2").ConfigurePrimaryHttpMessageHandler(() =>
{
return new HttpClientHandler
{
Proxy = new WebProxy("http://127.0.0.1:8889"),
UseProxy = true
};
});
...
然后:
public class MyService : IMyInterface
{
private readonly HttpClient _client;
public MyService(IHttpClientFactory httpClientFactory)
{
_client = httpClientFactory.CreateClient("MyServiceProxy1");
}
public async Task CallHttpEndpoint()
{
var request = new HttpRequestMessage(HttpMethod.Get, "www.customUrl.com");
var response = await _client.SendAsync(request);
...
}
}
我可以通过从 HttpClientHandler 继承来做到这一点:
public class ProxyHttpHandler : HttpClientHandler
{
private int currentProxyIndex = 0;
private ProxyOptions proxyOptions;
public ProxyHttpHandler(IOptions<ProxyOptions> options)
{
proxyOptions = options != null ? options.Value : throw new ArgumentNullException(nameof(options));
UseProxy = true;
}
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var proxy = proxyOptions.Proxies[currentProxyIndex];
var proxyResolver = new WebProxy(proxy.Host, proxy.Port)
{
Credentials = proxy.Credentials
};
Proxy = proxyResolver;
currentProxyIndex++;
if(currentProxyIndex >= proxyOptions.Proxies.Count)
currentProxyIndex = 0;
return base.SendAsync(request, cancellationToken);
}
}
然后我在 IoC 中注册我的ProxyHttpHandler
和ProxyOptions
:
public IForksCoreConfigurationBuilder ConfigureProxy(Action<ProxyOptions> options)
{
Services.AddOptions<ProxyOptions>().Configure(options);
Services.AddTransient<ProxyHttpHandler>();
Services.AddHttpClient<IService, MyService>()
.ConfigurePrimaryHttpMessageHandler<ProxyHttpHandler>();
return this;
}
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