企业级工作流解决方案（四）--微服务消息处理模型之消息传输通道

　　消息传输通道我这里只定义了3种，即：localInvoker，HttpInvoker，TcpInvoker，根据实际的情况，还可以进行扩展，比如消息队列，不过这都是后话了，先重点描述一下这3种方式。

LocalInvoker

　　本地调用直接构造请求参数，直接调用服务端的JsonRpcProcessor服务处理执行服务处理过程，这个不多说。

HttpInvoker

　　即执行http请求处理过程，由于.net framework和.net core的运行机制有所不同，处理方式也有所不同，但最终都落到服务端的JsonRpcProcessor身上进行处理，.net framework是通过增加IHttpAsyncHandler处理类处理调用请求，需要在web.config中增加处理handlers，

<add name="jsonrpc" type="CK.Sprite.JsonRpcFramework.JsonRpcHandler, CK.Sprite.JsonRpcFramework" verb="*" path="/json.rpc"/>

，实现类代码如下：

public class JsonRpcHandler : IHttpAsyncHandler
    {
        public IAsyncResult BeginProcessRequest(HttpContext context, AsyncCallback cb, object extraData)
        {
            context.Response.ContentType = "application/json";

            var async = new JsonRpcStateAsync(cb, context);
            async.JsonRpc = GetJsonRpcString(context.Request);
            JsonRpcProcessor.Process(async,context.Request);
            return async;
        }

        private static string GetJsonRpcString(System.Web.HttpRequest request)
        {
            string json = string.Empty;
            if (request.RequestType == "GET")
            {
                json = request.Params["jsonrpc"] ?? string.Empty;
            }
            else if (request.RequestType == "POST")
            {
                if (request.ContentType == "application/x-www-form-urlencoded")
                {
                    json = request.Params["jsonrpc"] ?? string.Empty;
                }
                else
                {
                    json = new StreamReader(request.InputStream).ReadToEnd();
                }
            }
            return json;
        }
    }

　　.net core这边的做法是增加RpcHttpRouter类，实现IRouter接口，并在StartUp的Configure方法中，增加处理Router，最终处理还是落到JsonRpcProcessor身上进行处理，代码如下：

public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            app.UseAbp(); //Initializes ABP framework. Should be called first.
            // ......
            app.Map("/json.rpc", rpcApp =>
            {
                rpcApp.UseJsonRpc();
            });
        }
public static IApplicationBuilder UseJsonRpc(this IApplicationBuilder app)
        {
            if (app == null)
            {
                throw new ArgumentNullException(nameof(app));
            }
            var router = new RpcHttpRouter();
            return app.UseRouter(router);
        }
public class RpcHttpRouter : IRouter
    {
        public VirtualPathData GetVirtualPath(VirtualPathContext context)
        {
            return null;
        }

        /// <summary>
        /// Takes a route/http contexts and attempts to parse, invoke, respond to an Rpc request
        /// </summary>
        /// <param name="context">Route context</param>
        /// <returns>Task for async routing</returns>
        public async Task RouteAsync(RouteContext context)
        {
            try
            {
                string jsonString = await GetJsonRpcString(context);

                string responseJson = await JsonRpcProcessor.Process(jsonString);

                if (string.IsNullOrEmpty(responseJson))
                {
                    //No response required, but status code must be 204
                    context.HttpContext.Response.StatusCode = 204;
                    context.MarkAsHandled();
                    return;
                }

                context.HttpContext.Response.ContentType = "application/json";
                await context.HttpContext.Response.WriteAsync(responseJson);

                context.MarkAsHandled();

            }
            catch (Exception ex)
            {
                context.MarkAsHandled();
            }
        }

        private async Task<string> GetJsonRpcString(RouteContext context)
        {
            string jsonString;
            if (context.HttpContext.Request.Body == null)
            {
                jsonString = null;
            }
            else
            {
                using (StreamReader streamReader = new StreamReader(context.HttpContext.Request.Body, Encoding.UTF8,
                    detectEncodingFromByteOrderMarks: true,
                    bufferSize: 1024,
                    leaveOpen: true))
                {
                    try
                    {
                        jsonString = await streamReader.ReadToEndAsync();
                    }
                    catch (TaskCanceledException ex)
                    {
                        throw new CPlatformException("Cancelled while reading the request.", ex);
                    }
                    jsonString = jsonString.Trim();
                }

            }

            return jsonString;
        }
    }

    public static class RouteContextExtensions
    {
        public static void MarkAsHandled(this RouteContext context)
        {
            context.Handler = c => Task.FromResult(0);
        }
    }

TcpInvoker

　　Tcp方式的调用后续文章会继续进行分解，也是微服务核心价值的地方。