深入淺出Blazor webassembly之HttpClient使用

===================================
參考
===================================

http://www.rzrgm.cn/deepthought/p/11303015.html

http://www.rzrgm.cn/willick/p/net-core-httpclient.html

技術(shù)譯民翻譯的博客 http://www.rzrgm.cn/ittranslator/p/making-http-requests-in-blazor-webassembly-apps.html

===================================
直接使用 HttpClient 的問(wèn)題
===================================

HttpClient 類所在庫(kù)為 System.Net.Http,

Blazor webassembly 默認(rèn)模版已經(jīng)自動(dòng)將HttpClient 注冊(cè)到DI 容器中了, 使用起來(lái)非常方便. Program.Main 函數(shù)注冊(cè)DI容器代碼:

builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });

直接使用 HttpClient 問(wèn)題有:

HttpClient 主要問(wèn)題是, 即使 Dispose 之后, 也不能即時(shí)關(guān)閉 socket 連接, 在 windows 下, 默認(rèn)需要等 240秒之后才能關(guān)閉 socket. 短時(shí)大量使用 HttpClient, 會(huì)將客戶端和服務(wù)器端 socket 連接消耗殆盡, 詳見(jiàn)參考文檔1的分析. 所以, 客戶端應(yīng)用程序一般使用單例模式使用 HttpClient 類. Blazor webassembly 也是如此.

如果使用單例模式, 如要為不同url 設(shè)置不同的 header, 就很不方便.
HttpClient 還會(huì)緩存 IP, 如果 DNS 之后有更新, HttpClient 仍會(huì)使用老的 IP

Net Core2.1 提供的 IHttpClientFactory 解決了直接使用HttpClient的所有問(wèn)題, IHttpClientFactory 提供了更優(yōu)雅 Http Client 功能.

===================================
IHttpClientFactory 簡(jiǎn)單方法生成 HttpClient
===================================

IHttpClientFactory 所在的類庫(kù)是 Microsoft.Extensions.Http , 將它加到blazor wasm 項(xiàng)目的依賴中,

Program.Main 函數(shù)必須使用 AddHttpClient 完成DI容器注冊(cè), 這樣DI容器就能為我們注入 IHttpClientFactory 實(shí)例.

builder.Services.AddHttpClient();

Razor 頁(yè)面使用 IHttpClientFactory 的實(shí)例生成 HttpClient 對(duì)象.

@page "/hello"
@inject IHttpClientFactory HttpClientFactory
<div>
    _statusCode: @_statusCode
</div>

@code{

    private string _statusCode = "";
    protected override async Task   OnInitializedAsync()
    {
        var httpClient = HttpClientFactory.CreateClient();

        //gorest.co.in 網(wǎng)站已經(jīng)開(kāi)啟 CORS 共享, 所以我們用它來(lái)測(cè)試, 而不是 https://www.baidu.com
        httpClient.BaseAddress=new Uri("https://gorest.co.in");
        var result = await httpClient.GetAsync("/public/v1/users");
        _statusCode = result.StatusCode.ToString();
    }
}

使用這個(gè)簡(jiǎn)單的方式, IHttpClientFactory 注入的實(shí)例未經(jīng)任何初始化, 比如未設(shè)置BaseAddress參數(shù), 需要在使用該實(shí)例時(shí)候, 進(jìn)行各種設(shè)置, 代碼復(fù)用性較差.

===================================
IHttpClientFactory 采用命名方式生成 HttpClient
===================================

命名方式在使用友好性方面比簡(jiǎn)單方式好很多.

注冊(cè)DI容器時(shí), AddHttpClient()傳入名稱, 同時(shí)還可以為將來(lái)的HttpClient對(duì)象設(shè)置各種參數(shù).

使用時(shí), 先獲取注入的 IHttpClientFactory HttpClient實(shí)例, 然后CreateClient()傳入命名值即可得到經(jīng)過(guò)預(yù)設(shè)的HttpClient對(duì)象對(duì)象 , 不需要再進(jìn)行參數(shù)設(shè)置.

builder.Services.AddHttpClient(name: "gorest", c =>
    {
        c.BaseAddress = new Uri("https://gorest.co.in");
    }
);

@page "/hello"
@inject IHttpClientFactory HttpClientFactory
<div>
    _statusCode: @_statusCode
</div>

@code{

    private string _statusCode = "";
    protected override async Task   OnInitializedAsync()
    {
        var httpClient = HttpClientFactory.CreateClient(name: "gorest");  
        var result = await httpClient.GetAsync("/public/v1/users");
        _statusCode = result.StatusCode.ToString();
    }
}

===================================
IHttpClientFactory 采用類型化方式生成 HttpClient
===================================

類型化方式比命名方式更進(jìn)一步, 注冊(cè)DI容器時(shí), AddHttpClient()傳入一個(gè)泛型類型, 將HttpClient的各種設(shè)置轉(zhuǎn)移到泛型類中

這樣的好處時(shí), AddHttpClient() 方法更簡(jiǎn)單, 代碼內(nèi)聚性更好.

包裝了 HttpClient 的泛型類:

  public class GorestHttpService
    {
        private readonly HttpClient _httpClient;
        public GorestHttpService(HttpClient httpClient)
        {
            _httpClient = httpClient;
            _httpClient.BaseAddress = new Uri("https://gorest.co.in"); 
        }

        public  async Task<string> GetStatusCodeAsync()
        {
            var result = await _httpClient.GetAsync("/public/v1/users");
            return result.StatusCode.ToString();
        }
       
    }

Program.Main 函數(shù) AddHttpClient 完成DI容器注冊(cè)

builder.Services.AddHttpClient<GorestHttpService>();

Razor 代碼:

@page "/hello"
@inject GorestHttpService gorestHttpService
<div>
    _statusCode: @_statusCode
</div>

@code{

    private string _statusCode = "";
    protected override async Task   OnInitializedAsync()
    {
        var result = await gorestHttpService.GetStatusCodeAsync();
        _statusCode = result;
    }
}

===================================
為 HttpClient 增加 Header
===================================

如需要增加 Bearer Header, 可以通過(guò)為 httpClient.DefaultRequestHeaders.Authorization 屬性賦值.

public class GorestHttpService
{
    private readonly HttpClient _httpClient;
    public GorestHttpService(HttpClient httpClient)
    {
        _httpClient = httpClient;
        _httpClient.BaseAddress = new Uri("https://gorest.co.in");
        string token = "changeMe";  
        _httpClient.DefaultRequestHeaders.Authorization= new AuthenticationHeaderValue("Bearer", token);
    }

    public  async Task<string> GetStatusCodeAsync()
    {
        var result = await _httpClient.GetAsync("/public/v1/users");
        return result.StatusCode.ToString();
    }
   
}

Jwt token 使用 Bearer head, Basic 驗(yàn)證使用:

client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", "base64 user:pwd")

或者加Header 文本:

HttpClient.DefaultRequestHeaders.Add("Authorization", "Bearer <token>");

HttpClient.DefaultRequestHeaders.Add("Authorization", "Basic "+"base64 user:pwd")

===================================
開(kāi)放的 Rest api 服務(wù)
===================================

示例中使用了 GoRest 網(wǎng)站, 它是 Online REST API for Testing and Prototyping https://gorest.co.in/

一些簡(jiǎn)單的api網(wǎng)站 https://mixedanalytics.com/blog/list-actually-free-open-no-auth-needed-apis/

posted @ 2021-10-18 22:24 harrychinese 閱讀(2383) 評(píng)論(0) 收藏舉報(bào)

刷新頁(yè)面返回頂部

harrychinese

深入淺出Blazor webassembly之HttpClient使用

公告