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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 workDir = Environment.CurrentDirectory;\n",
    "var fullPath = System.IO.Path.GetFullPath(\"./Publish/HttpClientStudy.WebApp/HttpClientStudy.WebApp.exe\", workDir);\n",
    "fullPath.Display();\n",
    "var startMessage = AppUtility.RunWebApiExeFile(fullPath);\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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    "/*\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",
    "    var baseUrl = WebApiConfigManager.GetWebApiConfig().BaseUrl;\n",
    "\n",
    "    using(var client = new HttpClient())\n",
    "    {\n",
    "        //发送请求\n",
    "        var response = await client.GetAsync(baseUrl);\n",
    "        response.EnsureSuccessStatusCode();\n",
    "    }\n",
    "\n",
    "    //显示句柄\n",
    "    var displayValue = display($\"第 1 次请求，成功！\");\n",
    "\n",
    "    for(int i=0;i<10;i++)\n",
    "    {\n",
    "        using(var client = new HttpClient())\n",
    "        {\n",
    "            var response = await client.GetAsync(baseUrl);\n",
    "            response.EnsureSuccessStatusCode();\n",
    "            displayValue.Update($\"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": [
    "相比于直接new,实现了HttpClient的重用，`不推荐的`：\n",
    "\n",
    "缺点：\n",
    "  1. 不够灵活、优雅：特别是有多个系列的请求时；\n",
    "  \n",
    "优点：\n",
    "  1. 复用 HttpClient\n",
    "  2. 实现了HttpClient的重用，减少创建和销毁的开销"
   ]
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    "/*\n",
    "    静态类/属性\n",
    "*/\n",
    "\n",
    "public class HttpClientHelper\n",
    "{\n",
    "    public readonly static HttpClient StaticClient;\n",
    "\n",
    "    static HttpClientHelper()\n",
    "    {\n",
    "        SocketsHttpHandler handler = new SocketsHttpHandler()\n",
    "        {\n",
    "            PooledConnectionLifetime = TimeSpan.FromSeconds(30),\n",
    "        };\n",
    "\n",
    "        StaticClient = new HttpClient(handler);\n",
    "\n",
    "        //统一设置：请求头等\n",
    "\n",
    "        //统一错误处理\n",
    "\n",
    "        //当然这里也可以设置Pipline，不过这里就不演示了\n",
    "    } \n",
    "\n",
    "    public static async Task<HttpResponseMessage> GetAsync(string url)\n",
    "    {\n",
    "        return await StaticClient.GetAsync(url);\n",
    "    }\n",
    "\n",
    "    public static async Task<string> GetStringAsync(string url)\n",
    "    {\n",
    "        var response = await StaticClient.GetAsync(url);\n",
    "        response.EnsureSuccessStatusCode();\n",
    "        return await response.Content.ReadAsStringAsync();\n",
    "    }\n",
    "\n",
    "    public static async Task<HttpResponseMessage> PostAsync(string url, HttpContent content)\n",
    "    {\n",
    "        return await StaticClient.PostAsync(url, content);\n",
    "    }\n",
    "}\n",
    "\n",
    "{   //调用静态类\n",
    "    var baseUrl = WebApiConfigManager.GetWebApiConfig().BaseUrl;\n",
    "    var response = await HttpClientHelper.GetAsync(baseUrl+\"/api/Config/GetApiConfig\");\n",
    "    var content = await response.Content.ReadAsStringAsync();\n",
    "    Console.WriteLine(content);\n",
    "\n",
    "    var response2 = await HttpClientHelper.GetStringAsync(baseUrl+\"/api/Normal/GetAllAccounts\");\n",
    "    Console.WriteLine(response2);\n",
    "}"
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    "/*\n",
    "   单例实现1:\n",
    "   1. 私有构造函数，防止外部实例化\n",
    "   2. 使用静态只读变量存储类的实例，由.Net框架保证实例不变且线程安全\n",
    "   3. 密封类，拒绝继承，保证不被子类破坏\n",
    "*/\n",
    "\n",
    "// 使用Lazy<T>实现单例\n",
    "public sealed class HttpClientSingleton \n",
    "{\n",
    "    // 私有静态变量，用于存储类的实例\n",
    "    private  static  readonly  HttpClientSingleton  instance  =  new  HttpClientSingleton();\n",
    "    \n",
    "    //公共静态属性，用于获取类的实例\n",
    "    public  static  HttpClientSingleton  Instance\n",
    "    {\n",
    "        get\n",
    "        {\n",
    "            return  instance;\n",
    "        }\n",
    "    }\n",
    "\n",
    "    private  readonly  HttpClient  Client;\n",
    "\n",
    "    //私有构造函数，防止外部实例化\n",
    "    private HttpClientSingleton() \n",
    "    {\n",
    "        SocketsHttpHandler handler = new SocketsHttpHandler()\n",
    "        {\n",
    "            PooledConnectionLifetime = TimeSpan.FromSeconds(30),\n",
    "        };\n",
    "\n",
    "        Client = new HttpClient(handler);\n",
    "\n",
    "        //统一设置：请求头等\n",
    "\n",
    "        //统一错误处理\n",
    "\n",
    "        //可以使用IoC容器来管理\n",
    "\n",
    "        //当然这里也可以设置Pipline，不过这里就不演示了\n",
    "        Console.WriteLine(\"HttpClientSingleton 初始化一次\");\n",
    "    }\n",
    "\n",
    "    public async Task<HttpResponseMessage> GetAsync(string url)\n",
    "    {\n",
    "        return await Client.GetAsync(url);\n",
    "    }\n",
    "\n",
    "    public async Task<string> GetStringAsync(string url)\n",
    "    {\n",
    "        var response = await Client.GetAsync(url);\n",
    "        response.EnsureSuccessStatusCode();\n",
    "        return await response.Content.ReadAsStringAsync();\n",
    "    }\n",
    "}\n",
    "\n",
    "{ //调用示例\n",
    "\n",
    "    var baseUrl = WebApiConfigManager.GetWebApiConfig().BaseUrl;\n",
    "    var response = await HttpClientSingleton.Instance.GetAsync(baseUrl+\"/api/Config/GetApiConfig\");\n",
    "    var content = await response.Content.ReadAsStringAsync();\n",
    "    Console.WriteLine(content);\n",
    "\n",
    "    var response2 = await HttpClientSingleton.Instance.GetStringAsync(baseUrl+\"/api/Normal/GetAllAccounts\");\n",
    "    Console.WriteLine(response2);\n",
    "}"
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    "/*\n",
    "   单例实现2:\n",
    "   1. 私有构造函数，防止外部实例化\n",
    "   2. 使用Lazy<T>, 延迟实例化, 由.Net 框架保证线程安全\n",
    "   3. 密封类，拒绝继承，保证不被子类破坏\n",
    "*/\n",
    "\n",
    "// 由于静态初始化器是由 .NET  运行时在后台处理的，因此它是线程安全的，不需要额外的锁定机制。\n",
    "public sealed class HttpClientSingleton2\n",
    "{\n",
    "    private  static  readonly  Lazy<HttpClient>  _httpClientLazy  =  new  Lazy<HttpClient>(()  =>\n",
    "    {\n",
    "         SocketsHttpHandler handler = new SocketsHttpHandler()\n",
    "        {\n",
    "            PooledConnectionLifetime = TimeSpan.FromSeconds(30)\n",
    "        };\n",
    "\n",
    "        var  client  =  new  HttpClient(handler)\n",
    "        {\n",
    "            //  可以在这里配置HttpClient的实例，例如设置超时时间、基地址等\n",
    "            //Timeout  =  TimeSpan.FromSeconds(30),\n",
    "            //BaseAddress  =  new  Uri(\"https://api.example.com/\"),\n",
    "        };\n",
    "\n",
    "\n",
    "        //统一设置：请求头等\n",
    "\n",
    "        //统一错误处理\n",
    "\n",
    "        //可以使用IoC容器来管理\n",
    "\n",
    "        //当然这里也可以设置Pipline，不过这里就不演示了\n",
    "        Console.WriteLine(\"HttpClientSingleton2 初始化一次\");\n",
    "\n",
    "        return  client;\n",
    "    });\n",
    "\n",
    "    public  static  HttpClient  Instance  =>  _httpClientLazy.Value;\n",
    "\n",
    "    //  私有构造函数，防止外部实例化\n",
    "    private  HttpClientSingleton2()  {  }  \n",
    "\n",
    "    public async Task<HttpResponseMessage> GetAsync(string url)\n",
    "    {\n",
    "        return await _httpClientLazy.Value.GetAsync(url);\n",
    "    }\n",
    "\n",
    "    public async Task<string> GetStringAsync(string url)\n",
    "    {\n",
    "        var response = await _httpClientLazy.Value.GetAsync(url);\n",
    "        response.EnsureSuccessStatusCode();\n",
    "        return await response.Content.ReadAsStringAsync();\n",
    "    }\n",
    "}\n",
    "\n",
    "{ //调用示例\n",
    "\n",
    "    var baseUrl = WebApiConfigManager.GetWebApiConfig().BaseUrl;\n",
    "    var response = await HttpClientSingleton2.Instance.GetAsync(baseUrl+\"/api/Config/GetApiConfig\");\n",
    "    var content = await response.Content.ReadAsStringAsync();\n",
    "    Console.WriteLine(content);\n",
    "\n",
    "    var response2 = await HttpClientSingleton2.Instance.GetStringAsync(baseUrl+\"/api/Normal/GetAllAccounts\");\n",
    "    Console.WriteLine(response2);\n",
    "}"
   ]
  },
  {
   "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": [
    "把不同类别的请求分成不同的工具类，业务类直接封装成工具类的方法。类似类型化的客户端。 简单使用的话，`比较推荐`\n",
    "\n",
    "优点:\n",
    "  1. 复用HttpClient\n",
    "  2. 可以灵活的进行统一配置\n",
    "  3. 不同类别不同工具类，方便定制\n",
    "  4. 业务直接封装成工具类方法，调用方便、快捷\n",
    "\n",
    "缺点：\n",
    "  1. 工具类比较多，需要手动维护\n",
    "  2. 工具类方法比较多且和业务直接相关，需要手动维护\n"
   ]
  },
  {
   "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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