gRPC JSON转码

gRPC JSON 转码允许浏览器应用调用 gRPC 服务，就像它们是使用 JSON 的 RESTful API 一样。

• 浏览器应用不需要生成 gRPC 客户端或了解 gRPC 的任何信息。
• 通过使用 HTTP 元数据注释 .proto 文件，可从 gRPC 服务自动创建 RESTful API。
• 使应用可以同时支持 gRPC 和 JSON Web API，而无需重复为两者生成单独的服务。

OpenAPI与gRPC Server

OpenAPI（以前称为 Swagger）是一个与语言无关的规范，用于描述 API。 gRPC JSON 转码支持从转码 REST ful的 API 生成 OpenAPI。

实现Server端

通过VS新增GRPC Server，新增nuget包

  <ItemGroup>
    <PackageReference Include="Grpc.AspNetCore" Version="2.49.0" />
    <PackageReference Include="Microsoft.AspNetCore.Grpc.JsonTranscoding" Version="7.0.0" />
    <PackageReference Include="Microsoft.AspNetCore.Grpc.Swagger" Version="0.3.0" />
  </ItemGroup>

为api生成用于OpenAPI的注释XML文件，在Server.csproj文件中新增以下配置

<GenerateDocumentationFile>true</GenerateDocumentationFile>

Server的Program.cs中，开启JSON转码与Swagger

            var builder = WebApplication.CreateBuilder(args);

            // 开启JSON转码
            builder.Services.AddGrpc().AddJsonTranscoding();

            // 配置Swagger
            builder.Services.AddGrpcSwagger();
            builder.Services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1", new OpenApiInfo { Title = "gRPC transcoding", Version = "v1" });
                var filePath = Path.Combine(System.AppContext.BaseDirectory, "GrpcService4.xml");
                c.IncludeXmlComments(filePath);
                c.IncludeGrpcXmlComments(filePath, includeControllerXmlComments: true);
            });

            var app = builder.Build();

            //开启Swagger
            app.UseSwagger();
            app.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("/swagger/v1/swagger.json", "My API V1");
            });

            app.MapGrpcService<GreeterService>();
            app.MapGet("/", () => "Communication with gRPC endpoints must be made through a gRPC client. To learn how to create a client, visit: https://go.microsoft.com/fwlink/?linkid=2086909");

            app.Run();

下载GRPC JSON转码依赖的proto文件

https://github.com/dotnet/aspnetcore/blob/main/src/Grpc/JsonTranscoding/test/testassets/Sandbox/google/api/http.proto

https://github.com/dotnet/aspnetcore/blob/main/src/Grpc/JsonTranscoding/test/testassets/Sandbox/google/api/annotations.proto

并将文件放到项目的google/api/文件夹中。

修改greet.proto文件，通过option开启http选项，以一个get方法和一个post方法举例

syntax = "proto3";

import "google/api/annotations.proto";

option csharp_namespace = "GrpcService4";

package greet;

// The greeting service definition.
service Greeter {
  // Sends a greeting
  rpc SayHello (HelloRequest) returns (HelloReply){
     option (google.api.http) = {
      get: "/v1/greeter/{name}"
    };
  };

    // Sends a greeting
  rpc SayHelloPost (HelloRequestPost) returns (HelloReply){
     option (google.api.http) = {
      post: "/v1/greeter/post",
      body:"data"
    };
  };
}

// The request message containing the user's name.
message HelloRequest {
  string name = 1;
}

// The request message containing the user's name.
message HelloRequestPost {
  HelloRequestPostData data = 1;
}

message HelloRequestPostData{
    string name = 1;
    string gender = 2;
}

// The response message containing the greetings.
message HelloReply {
  string message = 1;
}

然后实现Server

using Grpc.Core;
using GrpcService4;

namespace GrpcService4.Services
{
    public class GreeterService : Greeter.GreeterBase
    {
        private readonly ILogger<GreeterService> _logger;
        public GreeterService(ILogger<GreeterService> logger)
        {
            _logger = logger;
        }

        public override Task<HelloReply> SayHello(HelloRequest request, ServerCallContext context)
        {
            return Task.FromResult(new HelloReply
            {
                Message = "Hello " + request.Name
            });
        }


        public override Task<HelloReply> SayHelloPost(HelloRequestPost request, ServerCallContext context)
        {
            return Task.FromResult(new HelloReply
            {
                Message = "Hello " + request.Data.Name
            });
        }
    }
}

至此server的json转码开启完成，运行服务，访问swagger，即可尝试http方式请求

在支持http方式的请求的情况下，同时支持grpc请求。

实现Client端

新增控制台项目，添加以下nuget

  <ItemGroup>
    <PackageReference Include="Google.Protobuf" Version="3.21.9" />
    <PackageReference Include="Grpc.Net.Client" Version="2.49.0" />
    <PackageReference Include="Microsoft.AspNetCore.Grpc.JsonTranscoding" Version="7.0.0" />
    <PackageReference Include="Grpc.Tools" Version="2.50.0">
      <PrivateAssets>all</PrivateAssets>
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
  </ItemGroup>

包含与server端相同的proto文件

  <ItemGroup>
    <Protobuf Include="Protos\greet.proto" GrpcServices="Client" />
  </ItemGroup>

尝试请求Server

        static async Task Main(string[] args)
        {
            using var channel = GrpcChannel.ForAddress("https://localhost:7167");
            var client = new Greeter.GreeterClient(channel);
            var reply = await client.SayHelloAsync(new HelloRequest { Name = "GreeterClient" });
            Console.WriteLine("Greeting: " + reply.Message);

            var replyPost = await client.SayHelloPostAsync(new HelloRequestPost { Data = new HelloRequestPostData { Name = "111" } });
            Console.WriteLine("Greeting: " + replyPost.Message);
            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        }   

source code:  https://github.com/cysnet/grpc-json-transcoding