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   "source": [
    "# HttpClient 初始化与生命周期管理"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "HttpClient 旨在实例化一次，并在应用程序的整个生命周期内重复使用。\n",
    "\n",
    "为实现复用，HttpClient类库默认使用连接池和请求管道，可以手动管理(连接池、配置管道、使用Polly); 结合IoC容器、工厂模式(提供了IHttpClientFactory类库)、复原库Polly,可以更加方便、完善的使用,这也是推荐的方法。"
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    "//全局设置，行运行一次，为后续准备\n",
    "#r \"nuget:System.Net.Http.Json\"\n",
    "#r \"nuget:Microsoft.Extensions.DependencyInjection\"\n",
    "#r \"./Publish/HttpClientStudy.Core/HttpClientStudy.Core.dll\"\n",
    "\n",
    "global using System.Net.Http;\n",
    "global using System.Net.Http.Headers;\n",
    "global using HttpClientStudy.Config;\n",
    "global using HttpClientStudy.Core;\n",
    "global using HttpClientStudy.Core.Utilities;\n",
    "\n",
    "//启动已发布的WebApi项目\n",
    "Console.WriteLine(\"启动WebApi项目\");\n",
    "var startMessage = DotnetCommondUtility.ExecuteCommand(\"exec\",\"./Publish/HttpClientStudy.WebApp/HttpClientStudy.WebApp.dll\");\n",
    "Console.WriteLine(startMessage);\n"
   ]
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   "source": [
    "## 1、手动管理：直接实例化-强烈不推荐"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "下面这种每次使用都实例化的用法是最常见、最`不推荐的`：\n",
    "\n",
    "因为HttpClient刚推出时不成熟及微软官方文档的示例代码是这种用法，再加上这种是最简单方便的使用方法，就造成很多人使用这种用法。\n",
    "这种方法有如下缺点：\n",
    "+ 1. 每次使用都实例化，造成性能开销大、容易内存泄露；\n",
    "+ 2. 并发量大、请求频繁时：网络端口会被耗尽 `Using包HttpClient,也只是在应用进程中释放了HttpClient实例，但http请求/响应是跨操作系统和网络的，而系统及网络问题在进程之上，不是进程所能处理的。`\n",
    "  \n",
    "优点：\n",
    "+ 1. 使用简单，好学易用；\n",
    "+ 2. 并发量小且请求不频繁时，问题不大；"
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   "source": [
    "/*\n",
    "    每次请求都实例化：并发量大、请求频繁进会耗尽套接字端口\n",
    "*/\n",
    "{ \n",
    "    using(var client = new HttpClient())\n",
    "    {\n",
    "        //发送请求\n",
    "        var response = await client.GetAsync(\"http://localhost\");\n",
    "        response.EnsureSuccessStatusCode();\n",
    "    }\n",
    "\n",
    "    //显示句柄\n",
    "    var displayValue = display($\"第 1 次请求，成功！\");\n",
    "\n",
    "    for(int i=0;i<10;i++)\n",
    "    {\n",
    "        using(var client = new HttpClient())\n",
    "        {\n",
    "            var response = await client.GetAsync(\"http://localhost\");\n",
    "            response.EnsureSuccessStatusCode();\n",
    "            displayValue.Update($\"第 {i+1} 次/ 共 10 次请求，成功！\");\n",
    "        }\n",
    "    }\n",
    "}"
   ]
  },
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   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 2、手动管理：静态类或单例"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 3、手动管理：多工具类(每类请求对应一种工具类或单例类)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 4、手动管理：可复原(Polly)请求"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 5、IoC容器管理：类型化的客户端"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 6、客户端工厂管理：IHttpClientFactory(需要结合IoC)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## 7、综合管理：工厂 + 类型化客户端 ＋ 请求管道 + Polly(默认使用 连接池和IoC容器)"
   ]
  }
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