ASP.NET Core中间件(Middleware)实现WCF SOAP服务端解析

ASP.NET Core中间件(Middleware)进阶学习实现SOAP 解析。

本篇将介绍实现ASP.NET Core SOAP服务端解析，而不是ASP.NET Core整个WCF host。

因为WCF中不仅仅只是有SOAP， 它还包含很多如消息安全性，生成WSDL，双工信道，非HTTP传输等。

ASP.NET Core 官方推荐大家使用RESTful Web API的解决方案提供网络服务。

SOAP 即 Simple Object AccessProtocol 也就是简单对象访问协议。

SOAP 呢，其指导理念是“唯一一个没有发明任何新技术的技术”，

是一种用于访问 Web 服务的协议。

因为 SOAP 基于XML 和 HTTP ，其通过XML 来实现消息描述，然后再通过 HTTP 实现消息传输。

SOAP 是用于在应用程序之间进行通信的一种通信协议。

因为是基于 XML 和HTTP 的，所以其独立于语言，独立于平台，并且因为 XML 的扩展性很好，所以基于 XML 的 SOAP 自然扩展性也不差。

通过 SOAP 可以非常方便的解决互联网中消息互联互通的需求，其和其他的 Web 服务协议构建起 SOA 应用的技术基础。

下面来正式开始 ASP.NET Core 实现SOAP 服务端解析。

新建项目

首先新建一个ASP.NET Core Web Application -》 SOAPService 然后再模板里选择 Web API。

然后我们再添加一个Class Library -》 CustomMiddleware

实现

下面我们来实现功能，首先在类库项目中添加以下引用

Install-Package Microsoft.AspNetCore.Http.Abstractions

Install-Package System.ServiceModel.Primitives

Install-Package System.Reflection.TypeExtensions

Install-Package System.ComponentModel

首先新建一个 ServiceDescription、ContractDescription和OperationDescription 类，这里需要注意的是ServiceDescription，ContractDescription和OperationDescription这里使用的是不能使用 System.ServiceModel.Description命名空间中的类型。它们是示例中简单的新类型。

ServiceDescription.cs

    public class ServiceDescription
    {
        public Type ServiceType { get; private set; }
        public IEnumerable<ContractDescription> Contracts { get; private set; }
        public IEnumerable<OperationDescription> Operations => Contracts.SelectMany(c => c.Operations);

        public ServiceDescription(Type serviceType)
        {
            ServiceType = serviceType;

            var contracts = new List<ContractDescription>();

            foreach (var contractType in ServiceType.GetInterfaces())
            {
                foreach (var serviceContract in contractType.GetTypeInfo().GetCustomAttributes<ServiceContractAttribute>())
                {
                    contracts.Add(new ContractDescription(this, contractType, serviceContract));
                }
            }

            Contracts = contracts;
        }
    }

ContractDescription.cs

    public class ContractDescription
    {
        public ServiceDescription Service { get; private set; }
        public string Name { get; private set; }
        public string Namespace { get; private set; }
        public Type ContractType { get; private set; }
        public IEnumerable<OperationDescription> Operations { get; private set; }

        public ContractDescription(ServiceDescription service, Type contractType, ServiceContractAttribute attribute)
        {
            Service = service;
            ContractType = contractType;
            Namespace = attribute.Namespace ?? "http://tempuri.org/"; // Namespace defaults to http://tempuri.org/
            Name = attribute.Name ?? ContractType.Name; // Name defaults to the type name

            var operations = new List<OperationDescription>();
            foreach (var operationMethodInfo in ContractType.GetTypeInfo().DeclaredMethods)
            {
                foreach (var operationContract in operationMethodInfo.GetCustomAttributes<OperationContractAttribute>())
                {
                    operations.Add(new OperationDescription(this, operationMethodInfo, operationContract));
                }
            }
            Operations = operations;
        }
    }

OperationDescription.cs

    public class OperationDescription
    {
        public ContractDescription Contract { get; private set; }
        public string SoapAction { get; private set; }
        public string ReplyAction { get; private set; }
        public string Name { get; private set; }
        public MethodInfo DispatchMethod { get; private set; }
        public bool IsOneWay { get; private set; }

        public OperationDescription(ContractDescription contract, MethodInfo operationMethod, OperationContractAttribute contractAttribute)
        {
            Contract = contract;
            Name = contractAttribute.Name ?? operationMethod.Name;
            SoapAction = contractAttribute.Action ?? $"{contract.Namespace.TrimEnd('/')}/{contract.Name}/{Name}";
            IsOneWay = contractAttribute.IsOneWay;
            ReplyAction = contractAttribute.ReplyAction;
            DispatchMethod = operationMethod;
        }
    }

添加完成后下面来新建一个中间件 SOAPMiddleware ，对于新建中间件可以参考我之前的文章：http://www.cnblogs.com/linezero/p/5529767.html

SOAPMiddleware.cs 代码如下：

    public class SOAPMiddleware
    {
        private readonly RequestDelegate _next;
        private readonly Type _serviceType;
        private readonly string _endpointPath;
        private readonly MessageEncoder _messageEncoder;
        private readonly ServiceDescription _service;
        private IServiceProvider serviceProvider;

        public SOAPMiddleware(RequestDelegate next, Type serviceType, string path, MessageEncoder encoder,IServiceProvider _serviceProvider)
        {
            _next = next;
            _serviceType = serviceType;
            _endpointPath = path;
            _messageEncoder = encoder;
            _service = new ServiceDescription(serviceType);
            serviceProvider = _serviceProvider;
        }

        public async Task Invoke(HttpContext httpContext)
        {
            if (httpContext.Request.Path.Equals(_endpointPath, StringComparison.Ordinal))
            {
                Message responseMessage;

                //读取Request请求信息
                var requestMessage = _messageEncoder.ReadMessage(httpContext.Request.Body, 0x10000, httpContext.Request.ContentType);
                var soapAction = httpContext.Request.Headers["SOAPAction"].ToString().Trim('"');
                if (!string.IsNullOrEmpty(soapAction))
                {
                    requestMessage.Headers.Action = soapAction;
                }
                //获取操作
                var operation = _service.Operations.Where(o => o.SoapAction.Equals(requestMessage.Headers.Action, StringComparison.Ordinal)).FirstOrDefault();
                if (operation == null)
                {
                    throw new InvalidOperationException($"No operation found for specified action: {requestMessage.Headers.Action}");
                }
                //获取注入的服务
                var serviceInstance = serviceProvider.GetService(_service.ServiceType);

                //获取操作的参数信息
                var arguments = GetRequestArguments(requestMessage, operation);

                // 执行操作方法
                var responseObject = operation.DispatchMethod.Invoke(serviceInstance, arguments.ToArray());

                var resultName = operation.DispatchMethod.ReturnParameter.GetCustomAttribute<MessageParameterAttribute>()?.Name ?? operation.Name + "Result";
                var bodyWriter = new ServiceBodyWriter(operation.Contract.Namespace, operation.Name + "Response", resultName, responseObject);
                responseMessage = Message.CreateMessage(_messageEncoder.MessageVersion, operation.ReplyAction, bodyWriter);

                httpContext.Response.ContentType = httpContext.Request.ContentType;
                httpContext.Response.Headers["SOAPAction"] = responseMessage.Headers.Action;

                _messageEncoder.WriteMessage(responseMessage, httpContext.Response.Body);
            }
            else
            {
                await _next(httpContext);
            }
        }

        private object[] GetRequestArguments(Message requestMessage, OperationDescription operation)
        {
            var parameters = operation.DispatchMethod.GetParameters();
            var arguments = new List<object>();

            // 反序列化请求包和对象
            using (var xmlReader = requestMessage.GetReaderAtBodyContents())
            {
                // 查找的操作数据的元素
                xmlReader.ReadStartElement(operation.Name, operation.Contract.Namespace);

                for (int i = 0; i < parameters.Length; i++)
                {
                    var parameterName = parameters[i].GetCustomAttribute<MessageParameterAttribute>()?.Name ?? parameters[i].Name;
                    xmlReader.MoveToStartElement(parameterName, operation.Contract.Namespace);
                    if (xmlReader.IsStartElement(parameterName, operation.Contract.Namespace))
                    {
                        var serializer = new DataContractSerializer(parameters[i].ParameterType, parameterName, operation.Contract.Namespace);
                        arguments.Add(serializer.ReadObject(xmlReader, verifyObjectName: true));
                    }
                }
            }

            return arguments.ToArray();
        }
    }

    public static class SOAPMiddlewareExtensions
    {
        public static IApplicationBuilder UseSOAPMiddleware<T>(this IApplicationBuilder builder, string path, MessageEncoder encoder)
        {
            return builder.UseMiddleware<SOAPMiddleware>(typeof(T), path, encoder);
        }
        public static IApplicationBuilder UseSOAPMiddleware<T>(this IApplicationBuilder builder, string path, Binding binding)
        {
            var encoder = binding.CreateBindingElements().Find<MessageEncodingBindingElement>()?.CreateMessageEncoderFactory().Encoder;
            return builder.UseMiddleware<SOAPMiddleware>(typeof(T), path, encoder);
        }
    }

这里对于输出的消息做了一个封装，以输出具有正确的元素名称的消息的主体。

添加一个 ServiceBodyWriter 类。

    public class ServiceBodyWriter : BodyWriter
    {
        string ServiceNamespace;
        string EnvelopeName;
        string ResultName;
        object Result;

        public ServiceBodyWriter(string serviceNamespace, string envelopeName, string resultName, object result) : base(isBuffered: true)
        {
            ServiceNamespace = serviceNamespace;
            EnvelopeName = envelopeName;
            ResultName = resultName;
            Result = result;
        }

        protected override void OnWriteBodyContents(XmlDictionaryWriter writer)
        {
            writer.WriteStartElement(EnvelopeName, ServiceNamespace);
            var serializer = new DataContractSerializer(Result.GetType(), ResultName, ServiceNamespace);
            serializer.WriteObject(writer, Result);
            writer.WriteEndElement();
        }
    }

这里对于中间件整个就完成了。

服务端

在服务端使用，这里你也可以新建一个Web 项目。

因为刚刚我们已经新建好了一个Web API项目，我们就直接拿来使用。

首先添加 CustomMiddleware 引用

在 SOAPService 中添加一个 CalculatorService 类

    public class CalculatorService : ICalculatorService
    {
        public double Add(double x, double y) => x + y;
        public double Divide(double x, double y) => x / y;
        public double Multiply(double x, double y) => x * y;
        public double Subtract(double x, double y) => x - y;
        public string Get(string str) => $"{str} Hello World!";
    }

    [ServiceContract]
    public interface ICalculatorService
    {
        [OperationContract]
        double Add(double x, double y);
        [OperationContract]
        double Subtract(double x, double y);
        [OperationContract]
        double Multiply(double x, double y);
        [OperationContract]
        double Divide(double x, double y);
        [OperationContract]
        string Get(string str);
    }

这里我为了方便将接口契约也放在CalculatorService 中，你也可以新建一个接口。

然后在 Startup.cs  的 ConfigureServices 中注入 CalculatorService

        public void ConfigureServices(IServiceCollection services)
        {
            // Add framework services.
            services.AddMvc();
            services.AddScoped<CalculatorService>();
        }

在Configure 方法中加入中间件

        public void Configure(IApplicationBuilder app, IHostingEnvironment env, ILoggerFactory loggerFactory)
        {
            loggerFactory.AddConsole(Configuration.GetSection("Logging"));
            loggerFactory.AddDebug();
            //加入一个/CalculatorService.svc 地址，绑定Http
            app.UseSOAPMiddleware<CalculatorService>("/CalculatorService.svc", new BasicHttpBinding());

            app.UseMvc();
        }

这样就完成了服务端编写。

客户端

新建一个 Console Application -》SOAPClient

添加如下引用：

Install-Package System.ServiceModel.Primitives

Install-Package System.Private.ServiceModel

Install-Package System.ServiceModel.Http

Program代码如下：

    public class Program
    {
        public static void Main(string[] args)
        {
            Random numGen = new Random();
            double x = numGen.NextDouble() * 20;
            double y = numGen.NextDouble() * 20;

            var serviceAddress = "http://localhost:5000/CalculatorService.svc";

            var client = new CalculatorServiceClient(new BasicHttpBinding(), new EndpointAddress(serviceAddress));
            Console.WriteLine($"{x} + {y} == {client.Add(x, y)}");
            Console.WriteLine($"{x} - {y} == {client.Subtract(x, y)}");
            Console.WriteLine($"{x} * {y} == {client.Multiply(x, y)}");
            Console.WriteLine($"{x} / {y} == {client.Divide(x, y)}");
            client.Get("Client");
        }
    }
    class CalculatorServiceClient : ClientBase<ICalculatorService>
    {
        public CalculatorServiceClient(Binding binding, EndpointAddress remoteAddress) : base(binding, remoteAddress) { }
        public double Add(double x, double y) => Channel.Add(x, y);
        public double Subtract(double x, double y) => Channel.Subtract(x, y);
        public double Multiply(double x, double y) => Channel.Multiply(x, y);
        public double Divide(double x, double y) => Channel.Divide(x, y);

        public void Get(string str)
        {
            Console.WriteLine(Channel.Get(str));
        }
    }

    [ServiceContract]
    public interface ICalculatorService
    {
        [OperationContract]
        double Add(double x, double y);
        [OperationContract]
        double Subtract(double x, double y);
        [OperationContract]
        double Multiply(double x, double y);
        [OperationContract]
        double Divide(double x, double y);
        [OperationContract]
        string Get(string str);
    }

编写好以后，分别对应到目录使用dotnet run执行程序。

成功建立了连接，也有返回。也就实现SOAP 的解析。

示例代码GitHub：https://github.com/linezero/Blog/tree/master/SOAPService

参考文档：https://blogs.msdn.microsoft.com/dotnet/2016/09/19/custom-asp-net-core-middleware-example/

如果你觉得本文对你有帮助，请点击“推荐”，谢谢。