Abp Vnext 动态(静态)API客户端源码解析-Toy模板网

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根据以往的经验，通过接口远程调用服务的原理大致如下：

服务端：根据接口定义方法的签名生成路由，并暴露Api。
客户端：根据接口定义方法的签名生成请求，通过HTTPClient调用。

这种经验可以用来理解ABP VNext自动API的方式，但如果不使用自动API并且控制器定义了路由的情况下，远程调用的路由地址就有可能跟服务端暴露的路由不一致，预料的结果应该会返回404，但是Abp vnext却能够正常工作。那么客户端在使用远程调用时，是如何知道实际调用方法的路由地址呢？下面我们来探究一下源码。

一.动态API客户端

下面是注册动态API客户端的源码，AddHttpClientProxies 方法传入两个参数：接口层程序集和远程服务名称。该方法主要是遍历所有继承 IRemoteService 接口的类型，并为它们注册动态代理。同时，将每个类型的实例与远程服务名称关联起来，以便在进行远程调用时能够根据类型获取到对应的远程配置。需要注意的是，如果配置不存在对应的远程服务名称，则采用默认配置。

context.Services.AddHttpClientProxies(
            typeof(IdentityApplicationContractsModule).Assembly,  //接口层程序集
            RemoteServiceName   //远程服务名称
        );
        
public static IServiceCollection AddHttpClientProxy(this IServiceCollection services, Type type, string remoteServiceConfigurationName = "Default", bool asDefaultService = true)
        {
            /*省略一些代码...*/
            Type type2 = typeof(DynamicHttpProxyInterceptor<>).MakeGenericType(type); //拦截器
            services.AddTransient(type2);
            Type interceptorAdapterType = typeof(AbpAsyncDeterminationInterceptor<>).MakeGenericType(type2);
            Type validationInterceptorAdapterType = typeof(AbpAsyncDeterminationInterceptor<>).MakeGenericType(typeof(ValidationInterceptor));
            if (asDefaultService)
            {
                //生成代理，依赖注入到容器
                services.AddTransient(type, (IServiceProvider serviceProvider) => ProxyGeneratorInstance.CreateInterfaceProxyWithoutTarget(type, (IInterceptor)serviceProvider.GetRequiredService(validationInterceptorAdapterType), (IInterceptor)serviceProvider.GetRequiredService(interceptorAdapterType)));
            }
                         
            services.AddTransient(typeof(IHttpClientProxy<>).MakeGenericType(type), delegate (IServiceProvider serviceProvider)
            {
                //生成代理，通过HttpClientProxy封装，依赖注入到容器
                object obj = ProxyGeneratorInstance.CreateInterfaceProxyWithoutTarget(type, (IInterceptor)serviceProvider.GetRequiredService(validationInterceptorAdapterType), (IInterceptor)serviceProvider.GetRequiredService(interceptorAdapterType));
                return Activator.CreateInstance(typeof(HttpClientProxy<>).MakeGenericType(type), obj);
            });
            return services;
        }

通过动态代理实例调用方法的时候，会先进入拦截器 DynamicHttpProxyInterceptor 的 InterceptAsync 方法。

 public override async Task InterceptAsync(IAbpMethodInvocation invocation)
    {
        var context = new ClientProxyRequestContext(     
            await GetActionApiDescriptionModel(invocation), //获取Api描述信息
            invocation.ArgumentsDictionary,
            typeof(TService));

        if (invocation.Method.ReturnType.GenericTypeArguments.IsNullOrEmpty())
        {
            await InterceptorClientProxy.CallRequestAsync(context);  
        }
        else
        {
            var returnType = invocation.Method.ReturnType.GenericTypeArguments[0];
            var result = (Task)CallRequestAsyncMethod
                .MakeGenericMethod(returnType)
                .Invoke(this, new object[] { context });

            invocation.ReturnValue = await GetResultAsync(result, returnType);  //调用CallRequestAsync泛型方法
        }
    }

先通过 GetActionApiDescriptionModel 方法获取到Api描述信息，将其封装进远程调用的上下文。接着调用 CallRequestAsync 方法真正进行远程请求。如果是泛型，则调用 CallRequestAsync 的泛型方法。让我们先来看看 GetActionApiDescriptionModel 方法是如何获取到Api描述信息的。

    protected virtual async Task<ActionApiDescriptionModel> GetActionApiDescriptionModel(IAbpMethodInvocation invocation)
    {
        var clientConfig = ClientOptions.HttpClientProxies.GetOrDefault(typeof(TService)) ??      //获取远程服务名称
                           throw new AbpException($"Could not get DynamicHttpClientProxyConfig for {typeof(TService).FullName}.");
        var remoteServiceConfig = await RemoteServiceConfigurationProvider.GetConfigurationOrDefaultAsync(clientConfig.RemoteServiceName);//获取远程服务端点配置
        var client = HttpClientFactory.Create(clientConfig.RemoteServiceName); //创建HttpClient

        return await ApiDescriptionFinder.FindActionAsync(   
            client,
            remoteServiceConfig.BaseUrl,  //远程服务地址
            typeof(TService),       
            invocation.Method
        );
    }

远程服务端点配置例如：

 "RemoteServices": {
    "Default": {
      "BaseUrl": "http://localhost:44388"
    },
   "XXXDemo"：{
     "BaseUrl": "http://localhost:44345"
     }

  },

根据接口类型获取到远程服务名称，再根据名称获取到服务端点配置。ApiDescriptionFinder 是 IApiDescriptionFinder 的实例，默认实现是 ApiDescriptionFinder。

public async Task<ActionApiDescriptionModel> FindActionAsync(
        HttpClient client,
        string baseUrl,
        Type serviceType,
        MethodInfo method)
    {
        var apiDescription = await GetApiDescriptionAsync(client, baseUrl); //获取Api描述信息并缓存结果

        //TODO: Cache finding?

        var methodParameters = method.GetParameters().ToArray();

        foreach (var module in apiDescription.Modules.Values)
        {
            foreach (var controller in module.Controllers.Values)
            {
                if (!controller.Implements(serviceType))  //不继承接口跳过，所以写控制器为什么需要要继承服务接口的作用之一便在于此
                {
                    continue;
                }

                foreach (var action in controller.Actions.Values)
                {
                    if (action.Name == method.Name && action.ParametersOnMethod.Count == methodParameters.Length) //签名是否匹配
                    {
                        /*省略部分代码 */
                    }
                }
            }
        }

        throw new AbpException($"Could not found remote action for method: {method} on the URL: {baseUrl}");
    }

    public virtual async Task<ApplicationApiDescriptionModel> GetApiDescriptionAsync(HttpClient client, string baseUrl)
    {
        return await Cache.GetAsync(baseUrl, () => GetApiDescriptionFromServerAsync(client, baseUrl)); //缓存结果
    }

   protected virtual async Task<ApplicationApiDescriptionModel> GetApiDescriptionFromServerAsync(
        HttpClient client,
        string baseUrl)
    {
        //构造请求信息
        var requestMessage = new HttpRequestMessage(
            HttpMethod.Get,
            baseUrl.EnsureEndsWith('/') + "api/abp/api-definition"
        );

        AddHeaders(requestMessage); //添加请求头

        var response = await client.SendAsync(   //发送请求并获取响应结果
            requestMessage,
            CancellationTokenProvider.Token
        );

        if (!response.IsSuccessStatusCode)
        {
            throw new AbpException("Remote service returns error! StatusCode = " + response.StatusCode);
        }

        var content = await response.Content.ReadAsStringAsync();

        var result = JsonSerializer.Deserialize<ApplicationApiDescriptionModel>(content, DeserializeOptions);

        return result;
    }

GetApiDescriptionAsync 方法包装了缓存，GetApiDescriptionFromServerAsync 才是真正去获取Api描述信息的方法，它传递了两个参数，一个是httpclient（作用无需多说），另一个是baseurl即远程服务端点地址。通过Get请求方式调用远程服务的 "api/abp/api-definition" 接口，获取到该服务所有API描述信息，然后根据远程调用服务类型跟方法签名找到对应的API描述信息。API描述信息包含了端点的实际路由，支持版本号，是否允许匿名访问等信息。到此API描述信息已经获取到，回过头来看看 CallRequestAsync 方法的实现。

public virtual async Task<T> CallRequestAsync<T>(ClientProxyRequestContext requestContext)
    {
        return await base.RequestAsync<T>(requestContext);
    }

    public virtual async Task<HttpContent> CallRequestAsync(ClientProxyRequestContext requestContext)
    {
        return await base.RequestAsync(requestContext);
    }

  protected virtual async Task<HttpContent> RequestAsync(ClientProxyRequestContext requestContext)
    {
        //获取远程服务名称
        var clientConfig = ClientOptions.Value.HttpClientProxies.GetOrDefault(requestContext.ServiceType) ?? throw new AbpException($"Could not get HttpClientProxyConfig for {requestContext.ServiceType.FullName}.");
        
        //获取远程服务端点配置
        var remoteServiceConfig = await RemoteServiceConfigurationProvider.GetConfigurationOrDefaultAsync(clientConfig.RemoteServiceName);

        var client = HttpClientFactory.Create(clientConfig.RemoteServiceName); 
        var apiVersion = await GetApiVersionInfoAsync(requestContext); //获取API版本
        var url = remoteServiceConfig.BaseUrl.EnsureEndsWith('/') + await GetUrlWithParametersAsync(requestContext, apiVersion);  //拼接完整的url
        var requestMessage = new HttpRequestMessage(requestContext.Action.GetHttpMethod(), url) //构造HTTP请求信息
        {
            Content = await ClientProxyRequestPayloadBuilder.BuildContentAsync(requestContext.Action, requestContext.Arguments, JsonSerializer, apiVersion)
        };

        AddHeaders(requestContext.Arguments, requestContext.Action, requestMessage, apiVersion); //添加请求头

        if (requestContext.Action.AllowAnonymous != true) //是否需要认证
        {
            await ClientAuthenticator.Authenticate(       //认证
                new RemoteServiceHttpClientAuthenticateContext(
                    client,
                    requestMessage,
                    remoteServiceConfig,
                    clientConfig.RemoteServiceName
                )
            );
        }

        HttpResponseMessage response;
        try
        {
            response = await client.SendAsync(   //发送请求
                requestMessage,
                HttpCompletionOption.ResponseHeadersRead /*this will buffer only the headers, the content will be used as a stream*/,
                GetCancellationToken(requestContext.Arguments)
            );
        }
        return response.Content;
    }

GetUrlWithParametersAsync 方法是根据API描述信息跟调用参数值拼接出完整的路由地址，比如user/{id}/?name=xxxxx，接着构造出HTTP请求信息，添加请求头，如果需要身份认证，则调用 ClientAuthenticator.Authenticate 方法，ClientAuthenticator 是 IRemoteServiceHttpClientAuthenticator 的实例，它的实现有多种，有【Volo.Abp.Http.Client.IdentityModel】模块的 IdentityModelRemoteServiceHttpClientAuthenticator 类，它是使用OAuth 2.0协议直接调用接口获取访问令牌。有【Volo.Abp.Http.Client.IdentityModel.Web】模块的 HttpContextIdentityModelRemoteServiceHttpClientAuthenticator 类，它是从当前请求上下文获取到当前登录用户的访问令牌。

 public override async Task Authenticate(RemoteServiceHttpClientAuthenticateContext context)
    {
        if (context.RemoteService.GetUseCurrentAccessToken() != false)
        {
            var accessToken = await GetAccessTokenFromHttpContextOrNullAsync(); //获取当前登录用户Token
            if (accessToken != null)
            {
                context.Request.SetBearerToken(accessToken);
                return;
            }
        }

        await base.Authenticate(context);
    }

如果远程调用需要传递当前登录用户令牌则可以引用【Volo.Abp.Http.Client.IdentityModel.Web】模块

[DependsOn(typeof(AbpHttpClientIdentityModelWebModule))]

端点配置例如：

  "RemoteServices": {
    "AbpMvcClient": {
      "BaseUrl": "http://localhost:44388",
      "UseCurrentAccessToken": "true"
    }
  }

AddHeaders 方法，请求头添加租户等信息

 protected virtual void AddHeaders(
        IReadOnlyDictionary<string, object> argumentsDictionary,
        ActionApiDescriptionModel action,
        HttpRequestMessage requestMessage,
        ApiVersionInfo apiVersion)
    {
        /*省略代码/*
        //TenantId
        if (CurrentTenant.Id.HasValue)
        {
            //TODO: Use AbpAspNetCoreMultiTenancyOptions to get the key
            requestMessage.Headers.Add(TenantResolverConsts.DefaultTenantKey, CurrentTenant.Id.Value.ToString());
        }
        /*省略代码/*
    }

要点

1.控制器要继承服务接口

2.如果采用内部网关， api/abp/api-definition 将会转发到某一个服务，所以就需要将所有微服务的Api层引用到该服务上（或者在内部网关），这样才能通过 api/abp/api-definition 接口获取到对应服务的API描述信息。否则就不能直接通过内部网关调用，需要配置不同的远程服务名称指向相应的服务上才能获取到API描述信息。

二.静态API客户端

静态API客户端跟动态API客户端不一样，静态API客户端是通过abp cli工具提前生成好调用类跟API描述文件，在生成的时候同样遵守动态API客户端获取API描述信息的规则（注意要点1,2）

生成后ClientProxies目录包含调用类跟 *generate-proxy.json 文件，*generate-proxy.json 文件包含了API描述信息。

生成的调用类如下：

[Dependency(ReplaceServices = true)]
[ExposeServices(typeof(IIdentityRoleAppService), typeof(IdentityRoleClientProxy))]
public partial class IdentityRoleClientProxy : ClientProxyBase<IIdentityRoleAppService>, IIdentityRoleAppService
{
    public virtual async Task<ListResultDto<IdentityRoleDto>> GetAllListAsync()
    {
        return await RequestAsync<ListResultDto<IdentityRoleDto>>(nameof(GetAllListAsync));
    }
}

protected virtual async Task RequestAsync(string methodName, ClientProxyRequestTypeValue arguments = null)
{
    await RequestAsync(BuildHttpProxyClientProxyContext(methodName, arguments));
}

  protected virtual ClientProxyRequestContext BuildHttpProxyClientProxyContext(string methodName, ClientProxyRequestTypeValue arguments = null)
    {
        if (arguments == null)
        {
            arguments = new ClientProxyRequestTypeValue();
        }

        var methodUniqueName = $"{typeof(TService).FullName}.{methodName}.{string.Join("-", arguments.Values.Select(x => TypeHelper.GetFullNameHandlingNullableAndGenerics(x.Key)))}"; 
        var action = ClientProxyApiDescriptionFinder.FindAction(methodUniqueName); //获取调用方法的API描述信息
        if (action == null)
        {
            throw new AbpException($"The API description of the {typeof(TService).FullName}.{methodName} method was not found!");
        }

        var actionArguments = action.Parameters.GroupBy(x => x.NameOnMethod).ToList();
        if (action.SupportedVersions.Any()) 
        {   
            //TODO: make names configurable
            actionArguments.RemoveAll(x => x.Key == "api-version" || x.Key == "apiVersion");
        }

        return new ClientProxyRequestContext(   //封装未远程调用上下文
            action,
                actionArguments
                .Select((x, i) => new KeyValuePair<string, object>(x.Key, arguments.Values[i].Value))
                .ToDictionary(x => x.Key, x => x.Value),
            typeof(TService));
    }

ClientProxyApiDescriptionFinder 是 IClientProxyApiDescriptionFinder 的实例。默认实现是 ClientProxyApiDescriptionFinder 。

该实例初始化时调用 GetApplicationApiDescriptionModel 方法从虚拟文件系统中读取所有的 *generate-proxy.json 文件获取到API描述信息。

 private ApplicationApiDescriptionModel GetApplicationApiDescriptionModel()
    {
        var applicationApiDescription = ApplicationApiDescriptionModel.Create();
        var fileInfoList = new List<IFileInfo>();
        GetGenerateProxyFileInfos(fileInfoList);

        foreach (var fileInfo in fileInfoList)
        {
            using (var streamReader = new StreamReader(fileInfo.CreateReadStream()))
            {
                var content = streamReader.ReadToEnd();

                var subApplicationApiDescription = JsonSerializer.Deserialize<ApplicationApiDescriptionModel>(content);

                foreach (var module in subApplicationApiDescription.Modules)
                {
                    if (!applicationApiDescription.Modules.ContainsKey(module.Key))
                    {
                        applicationApiDescription.AddModule(module.Value);
                    }
                }
            }
        }

        return applicationApiDescription;
    }

    private void GetGenerateProxyFileInfos(List<IFileInfo> fileInfoList, string path = "")
    {
        foreach (var directoryContent in VirtualFileProvider.GetDirectoryContents(path))
        {
            if (directoryContent.IsDirectory)
            {
                GetGenerateProxyFileInfos(fileInfoList, directoryContent.PhysicalPath);
            }
            else
            {
                if (directoryContent.Name.EndsWith("generate-proxy.json"))
                {
                    fileInfoList.Add(VirtualFileProvider.GetFileInfo(directoryContent.GetVirtualOrPhysicalPathOrNull()));
                }
            }
        }
    }

后面 RequestAsync 方法就跟动态API客户端一样了。