依赖注入:HttpClient还是HttpClientFactory? [英] Dependency injection: HttpClient or HttpClientFactory?

问题描述

在任何地方，我都能看到三种在DI中创建客户端(基本，命名，类型)的主要方法，但是我找不到注入IHttpClientFactory或HttpClient的方法(两者都可行).

Everywhere I can see three main approaches to create clients (basic, named, typed) in DI, but I have found nowhere if to inject IHttpClientFactory or HttpClient (both possible).

问题1 :请注入IHttpClientFactory或HttpClient有什么区别?

Q1: What is the difference between injecting IHttpClientFactory or HttpClient please?

第二季度:而且如果注入了IHttpClientFactory，我应该为每个呼叫使用factory.CreateClient()吗?

Q2: And if IHttpClientFactory is injected, should I use factory.CreateClient() for each call?

推荐答案

摘要

• HttpClient只能注入已键入的客户端
• 其他用途，您需要IHttpClientFactory
• 在两种情况下，HttpClientMessageHandler的生存期都由框架管理，因此您不必担心(错误地)处置HttpClients.

Summary

• HttpClient can only be injected inside Typed clients
• for other usages, you need IHttpClientFactory
• In both scenarios, the lifetime of HttpClientMessageHandler is managed by the framework, so you are not worried about (incorrectly) disposing the HttpClients.

要直接注入HttpClient，您需要注册将接收客户端的特定 Typed 服务:

In order to directly inject HttpClient, you need to register a specific Typed service that will receive the client:

services.AddHttpClient<GithubClient>(c => c.BaseAddress = new System.Uri("https://api.github.com"));

现在，我们可以将其注入键入 GithubClient

Now we can inject that inside the typed GithubClient

public class GithubClient
{
    public GithubClient(HttpClient client)
    {
        // client.BaseAddress is "https://api.github.com"
    }
}

您不能将HttpClient插入到AnotherClient内，因为它没有在AnotherClient

You can't inject the HttpClient inside AnotherClient, because it is not typed to AnotherClient

public class AnotherClient
{
    public AnotherClient(HttpClient client)
    {
        // InvalidOperationException, can't resolve HttpClient 
    }
}

但是，您可以:
1.注入IHttpClientFactory并调用CreateClient().此客户端会将BaseAddress设置为null.
2.或将AnotherClient配置为其他类型的客户端，例如，使用不同的BaseAdress.

You can, however:
1. Inject the IHttpClientFactory and call CreateClient(). This client will have BaseAddress set to null.
2. Or configure AnotherClient as a different typed client with, for example, a different BaseAdress.

根据您的评论，您正在注册命名客户端.仍然可以通过IHttpClientFactory.CreateClient()方法进行解析，但是您需要传递客户端的名称"

Based on your comment, you are registering a Named client. It is still resolved from the IHttpClientFactory.CreateClient() method, but you need to pass the 'name' of the client

注册

services.AddHttpClient("githubClient", c => c.BaseAddress = new System.Uri("https://api.github.com"));

用法

// note that we inject IHttpClientFactory
public HomeController(IHttpClientFactory factory)
{
    this.defaultClient = factory.CreateClient(); // BaseAddress: null
    this.namedClient = factory.CreateClient("githubClient"); // BaseAddress: "https://api.github.com"
}

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