Dapr 客戶端搭配 WebApiClientCore 玩耍服務呼叫

使用Dapr 客戶端處理服務呼叫，需要遵循的他的模式，通常程式碼是這個樣子的：

var client = DaprClient.CreateInvokeHttpClient(appId: "routing");

var response = await client.GetAsJsonAsync($"/accounts/{17}", cancellationToken);

var account = await response.Content.ReadFromJsonAsync<Account>(cancellationToken: cancellationToken);

我更希望是這樣子呼叫:

public interface IBank

{
[HttpGet("/accounts/{accountId}")]
Task<Account> GetUser(string accountId, CancellationToken cancellationToken = default);

[HttpPost("/deposit")]
Task<Account> Deposit([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);

[HttpPost("/withdraw")]
[RawReturn(Enable =true, EnsureSuccessStatusCode = false)]
Task<HttpResponseMessage> Withdraw([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);

}

var account = await bankClient.GetUser("17", cancellationToken);

我們可以用 Refit，RestEase 或者是 WebApiClientCore 來達到這樣的效果， 那麼在Dapr 裡面使用這些庫如何做到呢， 在Dapr的客戶端庫裡面有一個Handler 的官方實現：InvocationHandler。 搭配這個InvocationHandler 就可以和這幾個庫，在本文中，我們重點介紹Dapr Client 如何搭配 WebApiClientCore。

public interface IBank
{
[HttpGet("/accounts/{accountId}")]
Task<Account> GetUser(string accountId, CancellationToken cancellationToken = default);

[HttpPost("/deposit")]
Task<Account> Deposit([JsonContent] Transaction transaction, CancellationToken cancellationToken = default);

public class WebapiClientExample : Example
{
public override string DisplayName => "WebapiClient";

private IBank bankClient;

public WebapiClientExample(IBank bank)
       {
           bankClient = bank;
       }

public override async Task RunAsync(CancellationToken cancellationToken)
{
var options = new JsonSerializerOptions(JsonSerializerDefaults.Web);

// Scenario 1: Check if the account already exists.
           Account? account = null;
           try
           {
               account = await bankClient.GetUser("17", cancellationToken);
           }
           catch (ApiException ex)
           {
               // Account does not exist.
           }

Console.WriteLine($"Scenario 1: account '17' {(account is null ? "does not exist" : "already exists")}");

// Scenario 2: Deposit some money
           var transaction = new Transaction()
           {
               Amount = 100m,
               Id = "17",
           };

// read updated balance
account = await bankClient.Deposit(transaction, cancellationToken);
Console.WriteLine($"Scenario 2: account '17' has '{account?.Balance}' money");

// Scenario 3: Handle a validation error without exceptions
           transaction = new Transaction()
           {
               Amount = 1_000_000m,
               Id = "17",
           };
           HttpResponseMessage response = null;

response = await bankClient.Withdraw(transaction, cancellationToken);
           if (response.StatusCode != HttpStatusCode.BadRequest)
           {
               // We don't actually expect this example to succeed - we expect a 400
               Console.WriteLine("Something went wrong :(");
               return;
           }
           var problem = await response.Content.ReadFromJsonAsync<ProblemDetails>(cancellationToken: cancellationToken);
           Console.WriteLine($"Scenario 3: got the following errors:");
           foreach (var kvp in problem!.Errors)
           {
               Console.WriteLine($"{kvp.Key}: {string.Join(", ", kvp.Value)}");
           }
       }
   }

var services = new ServiceCollection();
services.AddTransient<Example, WebapiClientExample>();
services.AddLogging();

services
                 .AddScoped<InvocationHandler>()
                 .AddHttpApi<WebapiClientExample.IBank>(o => o.HttpHost = new Uri("http://bank"))
                 .AddHttpMessageHandler<InvocationHandler>();
            var serviceprovider = services.BuildServiceProvider();

程式碼的核心部分就在於上面紅色的部分，我們把InvocationHandler 加入到AddHttpApi ，就可以和 dapr 一起玩耍了。

Dapr 客戶端 搭配 WebApiClientCore 玩耍服務呼叫