ASP.NET Core 2.1 HTTPClientFactory使用的3种方法

1、直接使用HttpClientFactory

1）在Startup.cs中ConpService方法中注册HttpClient，代码如下，

services.AddHttpClient();

2）在API controller(控制器)中调用代码

public >ValuesController : Controller
{
  private readonly IHttpClientFactory _httpClientFactory;

  public ValuesController(IHttpClientFactory httpClientFactory)
  {
    _httpClientFactory = httpClientFactory;
  }

  [HttpGet]
  public async Task<ActionResult> Get()
  {
    var client = _httpClientFactory.CreateClient();
    client.BaseAddress = new Uri("http://api.github.com");
    string result = await client.GetStringAsync("/");
    return Ok(result);
  }
}

2、通过HttpClient名字调用HttpClientFactory

如果需要进行多个请求并且较复杂，则可以使用这种方式，很方便。

1）将HttpClient请求命名，代码如下，

services.AddHttpClient();
services.AddHttpClient("github", c =>
{
  c.BaseAddress = new Uri("https://api.github.com/");
  c.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");
  c.DefaultRequestHeaders.Add("User-Agent", "HttpClientFactory-Sample");
});

2）在API controller(控制器)中调用命名的HttpClient

public >ValuesController : Controller
{
  private readonly IHttpClientFactory _httpClientFactory;

  public ValuesController(IHttpClientFactory httpClientFactory)
  {
    _httpClientFactory = httpClientFactory;
  }

  [HttpGet]
  public async Task<ActionResult> Get()
  {
    var client = _httpClientFactory.CreateClient("github");
    string result = await client.GetStringAsync("/");
    return Ok(result);
  }
}

3、使用自定义类执行HttpClientFactory请求

1）自定义HttpClientFactory请求类

public >GitHubClient
{
  public HttpClient Client { get; private set; }
 
  public GitHubClient(HttpClient httpClient)
  {
    httpClient.BaseAddress = new Uri("https://api.github.com/");
    httpClient.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");
    httpClient.DefaultRequestHeaders.Add("User-Agent", "HttpClientFactory-Sample");
    Client = httpClient;
  }
}

2）在Startup.cs中ConpService方法中注册GitHubClient，代码如下，

services.AddHttpClient<GitHubClient>();

3）在API controller(控制器)中调用代码

public >ValuesController : Controller
{
  private readonly GitHubClient _gitHubClient;;

  public ValuesController(GitHubClient gitHubClient)
  {
    _gitHubClient = gitHubClient;
  }

  [HttpGet]
  public async Task<ActionResult> Get()
  {
    string result = await _gitHubClient.client.GetStringAsync("/");
    return Ok(result);
  }
}

4、完全封装HttpClient可以使用下面方法

1）自定义HttpClientFactory请求类

public interface IGitHubClient
{
  Task<string> GetData();
}

public >GitHubClient : IGitHubClient
{
  private readonly HttpClient _client;

  public GitHubClient(HttpClient httpClient)
  {
    httpClient.BaseAddress = new Uri("https://api.github.com/");
    httpClient.DefaultRequestHeaders.Add("Accept", "application/vnd.github.v3+json");
    httpClient.DefaultRequestHeaders.Add("User-Agent", "HttpClientFactory-Sample");
    _client = httpClient;
  }

  public async Task<string> GetData()
  {
    return await _client.GetStringAsync("/");
  }
}

2）在Startup.cs中ConpService方法中注册GitHubClient，代码如下，

services.AddHttpClient<IGitHubClient, GitHubClient>();

3）在API controller(控制器)中调用代码

public >ValuesController : Controller
{
  private readonly IGitHubClient _gitHubClient;;
  
  public ValuesController(IGitHubClient gitHubClient)
  {
    _gitHubClient = gitHubClient;
  }
  
  [HttpGet]
  public async Task<ActionResult> Get()
  {
    string result = await _gitHubClient.GetData();
    return Ok(result);
  }
}

注意：三种方法都必须在Startup.cs中ConpService方法中注册HttpClient