.NET6之MiniAPI(二十二)：HttpClient

说明：本篇不是说明HttpClient怎么使用，而以分享在asp.net core mini api框架下，HttpClient的引入和使用方式。

我们在业务开发中，免不了调用三方的服务，这时就会用到HttpClient，在早期的asp.net core框架中，一般是通过new HttpClient来实现对三方的请求，现在，可以通过HttPClientFactory来实现，这样的好处是可以池化连接，节省资源。

基础使用方法很简单：

var builder = WebApplication.CreateBuilder(args);builder.Services.AddHttpClient();var app = builder.Build();app.MapGet("/test", async (IHttpClientFactory clientFactory) => {     var client = clientFactory.CreateClient();     var content = await client.GetStringAsync("https://www.google.com"); });app.Run();

当项目中有多个三方服务请求，为了区分各个三方服务，可以采用命名方式

var builder = WebApplication.CreateBuilder(args);builder.Services.AddHttpClient("Google", httpClient =>{    httpClient.BaseAddress = new Uri("https://www.google.com/");});builder.Services.AddHttpClient("BaiDu", httpClient =>{    httpClient.BaseAddress = new Uri("https://www.baidu.com/");});var app = builder.Build();app.MapGet("/testgoogle", async (IHttpClientFactory clientFactory) => {     var googleClient = clientFactory.CreateClient("Google");     return await googleCclient.GetStringAsync("search?q=桂素伟"); });app.MapGet("/testbaidu", async (IHttpClientFactory clientFactory) =>{    var baiduClient = clientFactory.CreateClient("BaiDu");    return await lient .GetStringAsync("s?wd=桂素伟");});app.Run();

还可以项目中每个服务的请求各自封装，各用各的HttpClient:

var builder = WebApplication.CreateBuilder(args);builder.Services.AddHttpClient<IGoogleService, GoogleService>();builder.Services.AddHttpClient<IBaiDuService, BaiDuService>(httpClient =>{    httpClient.BaseAddress = new Uri("https://www.baidu.com/");});var app = builder.Build();app.MapGet("/testgoogle", async (IGoogleService google) => {     return await google.GetContentAsync(); });app.MapGet("/testbaidu", async (IBaiDuService baidu) =>{    return await baidu.GetContentAsync();});app.Run();interface IGoogleService{    Task<string> GetContentAsync();}class GoogleService : IGoogleService{    private readonly HttpClient _httpClient;    public GoogleService(HttpClient httpClient)    {        _httpClient = httpClient;        _httpClient.BaseAddress = new Uri("https://www.google.com/");    }    public async Task<string> GetContentAsync()    {        return await _httpClient.GetStringAsync("search?q=桂素伟");    }}interface IBaiDuService{    Task<string> GetContentAsync();}class BaiDuService : IBaiDuService{    private readonly HttpClient _httpClient;    public BaiDuService(HttpClient httpClient)    {        _httpClient = httpClient;    }    public async Task<string> GetContentAsync()    {        return await _httpClient.GetStringAsync("s?wd=桂素伟");    }}