基于.net core 的微服务,网上很多介绍都是千篇一律基于类似webapi,通过http请求形式进行访问,但这并不符合大家使用习惯.如何像使用本地引用方式调用远程的服务,本文或许是一种参考.

1. 背景

           原项目基于传统三层模式组织代码逻辑,随着时间的推移,项目内各模块逻辑互相交织,互相依赖,维护起来较为困难.为此我们需要引入一种新的机制来尝试改变这个现状,在考察了 Java spring cloud/doubbo, c# wcf/webapi/asp.net core 等一些微服务框架后,我们最终选择了基于 .net core + Ocelot 微服务方式. 经过讨论大家最终期望的项目结果大致如下所示.

   
   
   

         但原项目团队成员已经习惯了基于接口服务的这种编码形式, 让大家将需要定义的接口全部以http 接口形式重写定义一遍, 同时客户端调用的时候, 需要将原来熟悉的形如 XXService.YYMethod(args1, args2) 直接使用通过 “.”出内部成员,替换为让其直接写 HttpClient.Post(“url/XX/YY”,”args1=11&args2=22”)的形式访问远程接口,确实是一件十分痛苦的事情.

2. 问题提出

        基于以上, 如何通过一种模式来简化这种调用形式, 继而使大家在调用的时候不需要关心该服务是在本地(本地类库依赖)还是远程, 只需要按照常规方式使用即可, 至于是直接使用本地服务还是通过http发送远程请求,这个都交给框架处理.为了方便叙述, 本文假定以销售订单和用户服务为例. 销售订单服务对外提供一个创建订单的接口.订单创建成功后, 调用用户服务更新用户积分.UML参考如下.
   

3. 问题转化

1. 在客户端,通过微服务对外公开的接口,生成接口代理, 即将接口需要的信息[接口名/方法名及该方法需要的参数]包装成http请求向远程服务发起请求.
2. 在微服务http接入段, 我们可以定义一个统一的入口,当服务端收到请求后,解析出接口名/方法名及参数信息,并创建对应的实现类,从而执行接口请求,并将返回值通过http返回给客户端.
3. 最后,客户端通过类似 AppRuntims.Instance.GetService<IOrderService>().SaveOrder(orderInfo) 形式访问远程服务创建订单.
4. 数据以json格式传输.

4. 解决方案及实现

1. 为了便于处理,我们定义了一个空接口IApiService,用来标识服务接口.

2. 远程服务客户端代理

   public class RemoteServiceProxy : IApiService
   {
       public string Address { get; set; }  //服务地址private ApiActionResult PostHttpRequest(string interfaceId, string methodId, params object[] p)
       {
           ApiActionResult apiRetult = null;
           using (var httpClient = new HttpClient())
           {
               var param = new ArrayList(); //包装参数
   
               foreach (var t in p)
               {
                   if (t == null)
                   {
                       param.Add(null);
                   }
                   else
                   {
                       var ns = t.GetType().Namespace;
                       param.Add(ns != null && ns.Equals("System") ? t : JsonConvert.SerializeObject(t));
                   }
               }
               var postContentStr = JsonConvert.SerializeObject(param);
               HttpContent httpContent = new StringContent(postContentStr);
               if (CurrentUserId != Guid.Empty)
               {
                   httpContent.Headers.Add("UserId", CurrentUserId.ToString());
               }
               httpContent.Headers.Add("EnterpriseId", EnterpriseId.ToString());
               httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
   
               var url = Address.TrimEnd('/') + $"/{interfaceId}/{methodId}";
               AppRuntimes.Instance.Loger.Debug($"httpRequest:{url},data:{postContentStr}");
   
               var response = httpClient.PostAsync(url, httpContent).Result; //提交请求
   
               if (!response.IsSuccessStatusCode)
               {
                   AppRuntimes.Instance.Loger.Error($"httpRequest error:{url},statuscode:{response.StatusCode}");
                   throw new ICVIPException("网络异常或服务响应失败");
               }
               var responseStr = response.Content.ReadAsStringAsync().Result;
               AppRuntimes.Instance.Loger.Debug($"httpRequest response:{responseStr}");
   
               apiRetult = JsonConvert.DeserializeObject<ApiActionResult>(responseStr);
           }
           if (!apiRetult.IsSuccess)
           {
               throw new BusinessException(apiRetult.Message ?? "服务请求失败");
           }
           return apiRetult;
       }
   
       //有返回值的方法代理
       public T Invoke<T>(string interfaceId, string methodId, params object[] param)
       {
           T rs = default(T);
   
           var apiRetult = PostHttpRequest(interfaceId, methodId, param);
   
           try
           {
               if (typeof(T).Namespace == "System")
               {
                   rs = (T)TypeConvertUtil.BasicTypeConvert(typeof(T), apiRetult.Data);
               }
               else
               {
                   rs = JsonConvert.DeserializeObject<T>(Convert.ToString(apiRetult.Data));
               }
           }
           catch (Exception ex)
           {
               AppRuntimes.Instance.Loger.Error("数据转化失败", ex);
               throw;
           }
           return rs;
       }
   
       //没有返回值的代理
       public void InvokeWithoutReturn(string interfaceId, string methodId, params object[] param)
       {
           PostHttpRequest(interfaceId, methodId, param);
       }
   }

3. 远程服务端http接入段统一入口

   [Route("api/svc/{interfaceId}/{methodId}"), Produces("application/json")]
   public async Task<ApiActionResult> Process(string interfaceId, string methodId)
   {
       Stopwatch stopwatch = new Stopwatch();
       stopwatch.Start();
       ApiActionResult result = null;
       string reqParam = string.Empty;
       try
       {
           using (var reader = new StreamReader(Request.Body, Encoding.UTF8))
           {
               reqParam = await reader.ReadToEndAsync();
           }
           AppRuntimes.Instance.Loger.Debug($"recive client request:api/svc/{interfaceId}/{methodId},data:{reqParam}");
   
           ArrayList param = null;
           if (!string.IsNullOrWhiteSpace(reqParam))
           {
              //解析参数
               param = JsonConvert.DeserializeObject<ArrayList>(reqParam);
           } 
           //转交本地服务处理中心处理
           var data = LocalServiceExector.Exec(interfaceId, methodId, param);
           result = ApiActionResult.Success(data);
       }
       catch  BusinessException ex) //业务异常
       {
           result = ApiActionResult.Error(ex.Message);
       }
       catch (Exception ex)
       {
           //业务异常
           if (ex.InnerException is BusinessException)
           {
               result = ApiActionResult.Error(ex.InnerException.Message);
           }
           else
           {
               AppRuntimes.Instance.Loger.Error($"调用服务发生异常{interfaceId}-{methodId},data:{reqParam}", ex);
               result = ApiActionResult.Fail("服务发生异常");
           }
       }
       finally
       {
           stopwatch.Stop();
           AppRuntimes.Instance.Loger.Debug($"process client request end:api/svc/{interfaceId}/{methodId},耗时[ {stopwatch.ElapsedMilliseconds} ]毫秒");
       }
       //result.Message = AppRuntimes.Instance.GetCfgVal("ServerName") + " " + result.Message;
       result.Message = result.Message;
       return result;
   }

4. 本地服务中心通过接口名和方法名,找出具体的实现类的方法,并使用传递的参数执行,ps:因为涉及到反射获取具体的方法,暂不支持相同参数个数的方法重载.仅支持不同参数个数的方法重载.

   public static object Exec( string interfaceId, string methodId, ArrayList param)
   {

     //通过接口名,方法名以及方法参数个数寻找本地实现类的具体
   var svcMethodInfo = GetInstanceAndMethod(interfaceId, methodId, param.Count);
   var currentMethodParameters = new ArrayList();
   for (var i = 0; i < svcMethodInfo.Paramters.Length; i++)
   {
   var tempParamter = svcMethodInfo.Paramters[i];

   if (param[i] == null)
   {
   currentMethodParameters.Add(null);
   }
   else
   {
   if (!tempParamter.ParameterType.Namespace.Equals(“System“)

   || tempParamter.ParameterType.Name == “Byte[]“)
   {
   currentMethodParameters.Add(JsonConvert.DeserializeObject(Convert.ToString(param[i]),

   tempParamter.ParameterType));
   }
   else
   {
   currentMethodParameters.Add(TypeConvertUtil.BasicTypeConvert(tempParamter.ParameterType,

   param[i]));
   }
   }
   }  //执行
   return svcMethodInfo.Invoke(currentMethodParameters.ToArray());
   }

   private static InstanceMethodInfo GetInstanceAndMethod(string interfaceId, string methodId, int paramCount)
   {
   var methodKey = $“{interfaceId}_{methodId}_{paramCount}“;
   if (methodCache.ContainsKey(methodKey))
   {
   return methodCache[methodKey];
   }
   InstanceMethodInfo temp = null;

   var svcType = ServiceFactory.GetSvcType(interfaceId, true);
   if (svcType == null)
   {
   throw new ICVIPException($“找不到API接口的服务实现:{interfaceId}“);
   }
   var methods = svcType.GetMethods().Where(t => t.Name == methodId).ToList();
   if (methods.IsNullEmpty())
   {
   throw new ICVIPException($“在API接口[{interfaceId}]的服务实现中[{svcType.FullName}]找不到指定的方法:{methodId}“);
   }
   var method = methods.FirstOrDefault(t => t.GetParameters().Length == paramCount);
   if (method == null)
   {
   throw new BusinessException($“在API接口中[{interfaceId}]的服务实现[{svcType.FullName}]中,方法[{methodId}]参数个数不匹配“);
   }
   var paramtersTypes = method.GetParameters();

   object instance = null;
   try
   {
   instance = Activator.CreateInstance(svcType);
   }
   catch (Exception ex)
   {
   throw new BusinessException($“在实例化服务[{svcType}]发生异常,请确认其是否包含一个无参的构造函数“, ex);
   }
   temp = new InstanceMethodInfo()
   {
   Instance = instance,
   InstanceType = svcType,
   Key = methodKey,
   Method = method,
   Paramters = paramtersTypes
   };
   if (!methodCache.ContainsKey(methodKey))
   {
   lock (_syncAddMethodCacheLocker)
   {
   if (!methodCache.ContainsKey(methodKey))
   {
   methodCache.Add(methodKey, temp);
   }
   }
   }
   return temp;
   }

5. 服务配置,指示具体的服务的远程地址,当未配置的服务默认为本地服务.

   [
     {
       "ServiceId": "XZL.Api.IOrderService",
       "Address": "http://localhost:8801/api/svc"
     },
     {
       "ServiceId": "XZL.Api.IUserService",
       "Address": "http://localhost:8802/api/svc"
     } 
   ]

6. AppRuntime.Instance.GetService<TService>()的实现.

   private static List<(string typeName, Type svcType)> svcTypeDic;
   private static ConcurrentDictionary<string, Object> svcInstance = new ConcurrentDictionary<string, object>();
    
   public static TService GetService<TService>()
    {
        var serviceId = typeof(TService).FullName;
   
        //读取服务配置
        var serviceInfo = ServiceConfonfig.Instance.GetServiceInfo(serviceId);
        if (serviceInfo == null)
        {
            return (TService)Activator.CreateInstance(GetSvcType(serviceId));
        }
        else
        { 
            var rs = GetService<TService>(serviceId + (serviceInfo.IsRemote ? "|Remote" : ""), serviceInfo.IsSingle);
            if (rs != null && rs is RemoteServiceProxy)
            {
                var temp = rs as RemoteServiceProxy;
                temp.Address = serviceInfo.Address;     //指定服务地址
            }
            return rs;
        }
    }
   public static TService GetService<TService>(string interfaceId, bool isSingle)
   {
       //服务非单例模式
       if (!isSingle)
       {
           return (TService)Activator.CreateInstance(GetSvcType(interfaceId));
       }
   
       object obj = null;
       if (svcInstance.TryGetValue(interfaceId, out obj) && obj != null)
       {
           return (TService)obj;
       }
       var svcType = GetSvcType(interfaceId);
   
       if (svcType == null)
       {
           throw new ICVIPException($"系统中未找到[{interfaceId}]的代理类");
       }
       obj = Activator.CreateInstance(svcType);
   
       svcInstance.TryAdd(interfaceId, obj);
       return (TService)obj;
   }
   
   //获取服务的实现类
   public static Type GetSvcType(string interfaceId, bool? isLocal = null)
   {
       if (!_loaded)
       {
           LoadServiceType();
       }
       Type rs = null;
       var tempKey = interfaceId;
   
       var temp = svcTypeDic.Where(x => x.typeName == tempKey).ToList();
   
       if (temp == null || temp.Count == 0)
       {
           return rs;
       }
   
       if (isLocal.HasValue)
       {
           if (isLocal.Value)
           {
               rs = temp.FirstOrDefault(t => !typeof(RemoteServiceProxy).IsAssignableFrom(t.svcType)).svcType;
           }
           else
           {
               rs = temp.FirstOrDefault(t => typeof(RemoteServiceProxy).IsAssignableFrom(t.svcType)).svcType;
           }
       }
       else
       {
           rs = temp[0].svcType;
       }
       return rs;
   }

7. 为了性能影响,我们在程序启动的时候可以将当前所有的ApiService类型缓存.

   public static void LoadServiceType()
    {
        if (_loaded)
        {
            return;
        }
        lock (_sync)
        {
            if (_loaded)
            {
                return;
            } 
            try
            {
                svcTypeDic = new List<(string typeName, Type svcType)>();
                var path = AppDomain.CurrentDomain.RelativeSearchPath ?? AppDomain.CurrentDomain.BaseDirectory;
                var dir = new DirectoryInfo(path);
                var files = dir.GetFiles("XZL*.dll");
                foreach (var file in files)
                { 
                    var types = LoadAssemblyFromFile(file);
                    svcTypeDic.AddRange(types);
                } 
                _loaded = true;
            }
            catch
            {
                _loaded = false;
            }
        }
    }
   
   //加载指定文件中的ApiService实现
   private static List<(string typeName, Type svcType)> LoadAssemblyFromFile(FileInfo file)
   {
       var lst = new List<(string typeName, Type svcType)>();
       if (file.Extension != ".dll" && file.Extension != ".exe")
       {
           return lst;
       }
       try
       {
           var types = Assembly.Load(file.Name.Substring(0, file.Name.Length - 4))
                           .GetTypes()
                           .Where(c => c.IsClass && !c.IsAbstract && c.IsPublic);
           foreach (Type type in types)
           {
              //客户端代理基类
               if (type == typeof(RemoteServiceProxy))
               {
                   continue;
               }
   
               if (!typeof(IApiService).IsAssignableFrom(type))
               {
                   continue;
               }
   
              //绑定现类
               lst.Add((type.FullName, type));
   
               foreach (var interfaceType in type.GetInterfaces())
               {
                   if (!typeof(IApiService).IsAssignableFrom(interfaceType))
                   {
                       continue;
                   } 
       //绑定接口与实际实现类
                   lst.Add((interfaceType.FullName, type));  
               }
           }
       }
       catch
       {
       }
   
       return lst;
   }

8. 具体api远程服务代理示例

   public class UserServiceProxy : RemoteServiceProxy, IUserService
       {
           private string serviceId = typeof(IUserService).FullName;
   
           public void IncreaseScore(int userId,int score)
           {
               return InvokeWithoutReturn(serviceId, nameof(IncreaseScore), userId,score);
           }
          public UserInfo GetUserById(int userId)
           {
               return Invoke<UserInfo >(serviceId, nameof(GetUserById),  userId);
           }
   }

5. 结语

   经过以上改造后, 我们便可很方便的通过形如 AppRuntime.Instance.GetService<TService>().MethodXX()无感的访问远程服务, 服务是部署在远程还是在本地以dll依赖形式存在,这个便对调用者透明了.无缝的对接上了大家固有习惯.
   PS: 但是此番改造后, 遗留下来了另外一个问题: 客户端调用远程服务,需要手动创建一个服务代理( 从 RemoteServiceProxy 继承),虽然每个代理很方便写,只是文中提到的简单两句话,但终究显得繁琐, 是否有一种方式能够根据远程api接口动态的生成这个客户端代理呢? 答案是肯定的,因本文较长了,留在下篇再续.