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IHttpClientFactory.CreateClientÊÇÈçºÎ½«HttpClient´´½¨³öÀ´µÄ?

• ÿ´ÎCreateClient³öÀ´µÄ¶¼ÊÇÒ»¸öеÄHttpClientʵÀý
• ÔÚCreateHandlerÖеÄ_activeHandlers½«Îª365betÌåÓýÔÚÏßÃÇ»º´æ365betÌåÓýÔÚÏßÃǵÄhandler, ĬÈÏÊÇ2·ÖÖÓ(¶¨ÒåÔÚHttpClientFactoryOptions.HandlerLifetime)
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• CreateHandlerEntry·½·¨ÔòÊÇÕæÕýµÄ´´½¨ÒÔ¼°ÅäÖÃ365betÌåÓýÔÚÏßÃǵÄhandlersµÄµØ·½.
  • ´ÓIConfiguration»ñµÃÒ»¸öHttpClientFactoryOptions¶ÔÏó
  • Ó¦ÓÃ IHttpMessageHandlerBuilderFilter
  • Ó¦ÓÃ HttpMessageHandlerBuilderActions

//Microsoft.Extensions.Http.DefaultHttpClientFactory
public HttpClient CreateClient(string name)
{
	HttpClient httpClient = new HttpClient(this.CreateHandler(name), disposeHandler: false);
	return httpClient;
}
public HttpMessageHandler CreateHandler(string name)
{
	ActiveHandlerTrackingEntry value = this._activeHandlers.GetOrAdd(name, this._entryFactory).Value; 
        //_entryFactory¿ÉÒÔÖ±½ÓÀí½âΪÊÇCreateHandlerEntry·½·¨.ËüÕæʵµÄÀàÐÍÊÇLazy<>(CreateHandlerEntry,LazyThreadSafetyMode.ExecutionAndPublication)µÄ, Ò²¾ÍÊDz¢·¢°²È«µÄµ÷ÓÃCreateHandlerEntry.
	return value.Handler;
}
internal ActiveHandlerTrackingEntry CreateHandlerEntry(string name)
{
        HttpClientFactoryOptions options = this._optionsMonitor.Get(name);
	HttpMessageHandlerBuilder requiredService = provider.GetRequiredService<HttpMessageHandlerBuilder>();
	requiredService.Name = name;
	Action<HttpMessageHandlerBuilder> action = Configure; // À©Õ¹µã¶þ HttpClientFactoryOptions.HttpMessageHandlerBuilderActions
	for (int num = this._filters.Length - 1; num >= 0; num--)
	{
		action = this._filters[num].Configure(action); //À©Õ¹µãÒ» _filters(¹¹Ô캯Êý´«ÈëµÄIEnumerable<IHttpMessageHandlerBuilderFilter> filters).
	}
	action(requiredService);
	LifetimeTrackingHttpMessageHandler handler = new LifetimeTrackingHttpMessageHandler(requiredService.Build());
	return new ActiveHandlerTrackingEntry(name, handler, serviceScope, options.HandlerLifetime);

	void Configure(HttpMessageHandlerBuilder b)
	{
		for (int i = 0; i < options.HttpMessageHandlerBuilderActions.Count; i++)
		{
			options.HttpMessageHandlerBuilderActions[i](b);
		}
	}
}

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class MyHttpClientHandlerFilter : IHttpMessageHandlerBuilderFilter
{
    public Action<HttpMessageHandlerBuilder> Configure(Action<HttpMessageHandlerBuilder> next)
    {
        void Configure(HttpMessageHandlerBuilder builder)
        {
            next(builder); //Ò»¿ªÊ¼¾Íµ÷ÓÃnext, ÕâÑù365betÌåÓýÔÚÏßÃǵÄÕû¸öHandlerBuilderµÄÖ´ÐÐ˳Ðò¾ÍÊÇÒÀ´Îcall _filters, ×îºócall options.HttpMessageHandlerBuilderActions(À©Õ¹µã¶þ).

            if (builder.Name.StartsWith("CallbackProviderSide-")) //365betÌåÓýÔÚÏßÃÇ¿ÉÒÔΪÕâÀàÒµÎñͳһ¼ÓÒ»¸öǰ׺×öÇø±ð, ÕâÑù¾Í²»»áÓ°ÏìÆäËûµÄHttpClient¶ÔÏóÁË.
            {
                //builder.PrimaryHandler= your custom handler. ²Î¿¼¹Ù·½ÎĵµµÄʵÏÖ.
            }
        }
        return Configure;
    }
}
//È»ºóÔÚDIÈÝÆ÷ÖÐ×¢Èë365betÌåÓýÔÚÏßÃǵÄfilter.
ServiceCollection.AddSingleton<IHttpMessageHandlerBuilderFilter,MyHttpClientHandlerFilter>();

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class MyHttpClientCustomConfigure : IPostConfigureOptions<HttpClientFactoryOptions>
{
    public void PostConfigure(string name, HttpClientFactoryOptions options)
    {
        if (name.StartsWith("CallbackProviderSide-")) //365betÌåÓýÔÚÏßÃÇ¿ÉÒÔΪÕâÀàÒµÎñͳһ¼ÓÒ»¸öǰ׺×öÇø±ð, ÕâÑù¾Í²»»áÓ°ÏìÆäËûµÄHttpClient¶ÔÏóÁË.
        {
            options.HttpMessageHandlerBuilderActions.Add(p =>
            {
                //p.PrimaryHandler= your custom handler. ²Î¿¼¹Ù·½ÎĵµµÄʵÏÖ.
            });
        }
    }
}

//È»ºóÔÚDIÈÝÆ÷ÖÐ×¢Èë365betÌåÓýÔÚÏßÃǵÄÕâ¸öÅäÖÃÀ©Õ¹Àà.
ServiceCollection.AddSingleton<Microsoft.Extensions.Options.IPostConfigureOptions<Microsoft.Extensions.Http.HttpClientFactoryOptions>, MyHttpClientCustomConfigure>();

ΪʲôÕâÀï×¢ÈëµÄÀàÐÍÊÇMicrosoft.Extensions.Options.IPostConfigureOptions<Microsoft.Extensions.Http.HttpClientFactoryOptions>, ÊÇÒòΪOptionsFactoryËüµÄ¹¹Ô캯ÊýÐèÒªµÄ¾ÍÊÇÕâ¸ö. ÖÁÓÚÓйØConfigurationϵͳµÄÀ©Õ¹ºÍÔ´´úÂëÔÚÕâÀï¾Í²»ÔÚÕâÀïÕ¹¿ªÁË.

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var factory = ServiceProvider.GetService<IHttpClientFactory>();
var httpClientForBaidu = factory.CreateClient("CallbackProviderSide-baidu");
var httpClientForCnblogs = factory.CreateClient("CallbackProviderSide-Cnblogs");

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ÁíÍâ,ÓйØIHttpClientFactory±³ºóµÄ¹ÊÊ¿ÉÒԲ鿴ÎÄÕÂExploring the code behind IHttpClientFactory in depth, ºÜÍêÕûµÄÁ÷³ÌͼÔÚÅäÉÏ´úÂë, °ÑËü½²½âµÄÇåÇå³þ³þ.