c# - 在不更改 URI 模板反序列化的情况下使用自定义 WCF 正文反序列化

Question

来自 this blog post ，我能够创建一个使用 JSON.NET 序列化的自定义 WCF IDispatchMessageFormatter。它工作得很好，但有一个警告:将它与 UriTemplate 一起使用不一定会按预期工作。

这是博客文章提供的实现:

class NewtonsoftJsonDispatchFormatter : IDispatchMessageFormatter
{
    private readonly OperationDescription od;
    private readonly ServiceEndpoint ep;
    private readonly Dictionary<string, int> parameterNames = new Dictionary<string, int>();

    public NewtonsoftJsonDispatchFormatter(OperationDescription od, ServiceEndpoint ep, bool isRequest)
    {
        this.od = od;
        this.ep = ep;
        if (isRequest)
        {
            int operationParameterCount = od.Messages[0].Body.Parts.Count;
            if (operationParameterCount > 1)
            {
                this.parameterNames = new Dictionary<string, int>();
                for (int i = 0; i < operationParameterCount; i++)
                {
                    this.parameterNames.Add(od.Messages[0].Body.Parts[i].Name, i);
                }
            }
        }
    }
    public void DeserializeRequest(Message message, object[] parameters)
    {
        if (message.IsEmpty) 
            return;

        object bodyFormatProperty;

        if (!message.Properties.TryGetValue(WebBodyFormatMessageProperty.Name, out bodyFormatProperty) ||
            (bodyFormatProperty as WebBodyFormatMessageProperty).Format != WebContentFormat.Raw)
        {
            throw new InvalidOperationException("Incoming messages must have a body format of Raw. Is a ContentTypeMapper set on the WebHttpBinding?");
        }

        XmlDictionaryReader bodyReader = message.GetReaderAtBodyContents();
        bodyReader.ReadStartElement("Binary");
        byte[] rawBody = bodyReader.ReadContentAsBase64();

        using (MemoryStream ms = new MemoryStream(rawBody))
        using (StreamReader sr = new StreamReader(ms))
        {
            if (parameters.Length == 1)
                parameters[0] = Helper.serializer.Deserialize(sr, od.Messages[0].Body.Parts[0].Type);
            else
            {
                // multiple parameter, needs to be wrapped
                using (Newtonsoft.Json.JsonReader reader = new Newtonsoft.Json.JsonTextReader(sr))
                {
                    reader.Read();
                    if (reader.TokenType != Newtonsoft.Json.JsonToken.StartObject)
                        throw new InvalidOperationException("Input needs to be wrapped in an object");
                    reader.Read();
                    while (reader.TokenType == Newtonsoft.Json.JsonToken.PropertyName)
                    {
                        string parameterName = reader.Value as string;
                        reader.Read();
                        if (this.parameterNames.ContainsKey(parameterName))
                        {
                            int parameterIndex = this.parameterNames[parameterName];
                            parameters[parameterIndex] = Helper.serializer.Deserialize(reader, this.od.Messages[0].Body.Parts[parameterIndex].Type);
                        }
                        else
                            reader.Skip();
                        reader.Read();
                    }
                }
            }
        }
    }

     public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result) { ... }
}

基本上，DeserializeMethod 签名中的object[] 参数 是该方法需要实例化的out 参数。

因此，这可以很好地处理这样的 REST 端点:

[WebInvoke(Method="POST", UriTemplate="foo/")]
public Foo MakeFoo(Foo foo) { ... }

或者像这样:

[WebInvoke(Method="POST", UriTemplate="FooBar/")]
public FooBar FooBar(Foo foo, Bar bar) { .. }

但它目前没有将 URI 模板参数映射到方法参数，例如像这样:

[WebGet(UriTemplate="Foo/{id}")]
public Foo GetFoo(string id) { ... }

Microsoft 在覆盖的 GetRequestDispatchFormatter 上写入:

This is an extensibility point that derived behaviors can use to supply their own implementation of IDispatchMessageFormatter that is called to deserialize the input parameters of the service operation from the request message. Parameters specified in the UriTemplate of the service operation must be deserialized from the To URI of the request message and other parameters must be deserialized from the body of the request message.

太棒了。我更新了消息正文中参数的反序列化。但我不想覆盖 UriTemplate 中参数的反序列化。有什么方法可以使用现有代码将传入的 URI 请求映射到默认处理 UriTemplate 的参数？

看来我需要使用类似 UriTemplateDispatchFormatter 的东西但我不确定如何实现它，而且它是非公开的。

Answer 1

好吧，这可能是我不得不做的最荒谬的事情，但是复制 UriTemplateDispatchFormatter 的源代码，您可以简单地返回一个带有“inner"IDispatchFormatter 对应于我在此处提供的 IDispatchFormatter。不知道为什么这个类是内部的 >_>

下面的类定义:

class UriTemplateDispatchFormatter : IDispatchMessageFormatter
{
    internal Dictionary<int, string> pathMapping;
    internal Dictionary<int, KeyValuePair<string, Type>> queryMapping;
    Uri baseAddress;
    IDispatchMessageFormatter bodyFormatter;
    string operationName;
    QueryStringConverter qsc;
    int totalNumUTVars;
    UriTemplate uriTemplate;

    public UriTemplateDispatchFormatter(OperationDescription operationDescription, IDispatchMessageFormatter bodyFormatter, QueryStringConverter qsc, string contractName, Uri baseAddress)
    {
        this.bodyFormatter = bodyFormatter;
        this.qsc = qsc;
        this.baseAddress = baseAddress;
        this.operationName = operationDescription.Name;
        Populate(
            out this.pathMapping,
            out this.queryMapping,
            out this.totalNumUTVars,
            out this.uriTemplate,
            operationDescription,
            qsc,
            contractName);
    }

    public void DeserializeRequest(Message message, object[] parameters)
    {
        object[] bodyParameters = new object[parameters.Length - this.totalNumUTVars];

        if (bodyParameters.Length != 0)
        {
            this.bodyFormatter.DeserializeRequest(message, bodyParameters);
        }
        int j = 0;
        UriTemplateMatch utmr = null;
        string UTMRName = "UriTemplateMatchResults";
        if (message.Properties.ContainsKey(UTMRName))
        {
            utmr = message.Properties[UTMRName] as UriTemplateMatch;
        }
        else
        {
            if (message.Headers.To != null && message.Headers.To.IsAbsoluteUri)
            {
                utmr = this.uriTemplate.Match(this.baseAddress, message.Headers.To);
            }
        }
        NameValueCollection nvc = (utmr == null) ? new NameValueCollection() : utmr.BoundVariables;
        for (int i = 0; i < parameters.Length; ++i)
        {
            if (this.pathMapping.ContainsKey(i) && utmr != null)
            {
                parameters[i] = nvc[this.pathMapping[i]];
            }
            else if (this.queryMapping.ContainsKey(i) && utmr != null)
            {
                string queryVal = nvc[this.queryMapping[i].Key];
                parameters[i] = this.qsc.ConvertStringToValue(queryVal, this.queryMapping[i].Value);
            }
            else
            {
                parameters[i] = bodyParameters[j];
                ++j;
            }
        }
    }


    public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result)
    {
        throw new NotImplementedException();
    }

    private static void Populate(out Dictionary<int, string> pathMapping,
    out Dictionary<int, KeyValuePair<string, Type>> queryMapping,
    out int totalNumUTVars,
    out UriTemplate uriTemplate,
    OperationDescription operationDescription,
    QueryStringConverter qsc,
    string contractName)
    {
        pathMapping = new Dictionary<int, string>();
        queryMapping = new Dictionary<int, KeyValuePair<string, Type>>();
        string utString = GetUTStringOrDefault(operationDescription);
        uriTemplate = new UriTemplate(utString);
        List<string> neededPathVars = new List<string>(uriTemplate.PathSegmentVariableNames);
        List<string> neededQueryVars = new List<string>(uriTemplate.QueryValueVariableNames);
        Dictionary<string, byte> alreadyGotVars = new Dictionary<string, byte>(StringComparer.OrdinalIgnoreCase);
        totalNumUTVars = neededPathVars.Count + neededQueryVars.Count;
        for (int i = 0; i < operationDescription.Messages[0].Body.Parts.Count; ++i)
        {
            MessagePartDescription mpd = operationDescription.Messages[0].Body.Parts[i];
            string parameterName = XmlConvert.DecodeName(mpd.Name);
            if (alreadyGotVars.ContainsKey(parameterName))
            {
                throw new InvalidOperationException();
            }
            List<string> neededPathCopy = new List<string>(neededPathVars);
            foreach (string pathVar in neededPathCopy)
            {
                if (string.Compare(parameterName, pathVar, StringComparison.OrdinalIgnoreCase) == 0)
                {
                    if (mpd.Type != typeof(string))
                    {
                        throw new InvalidOperationException();
                    }
                    pathMapping.Add(i, parameterName);
                    alreadyGotVars.Add(parameterName, 0);
                    neededPathVars.Remove(pathVar);
                }
            }
            List<string> neededQueryCopy = new List<string>(neededQueryVars);
            foreach (string queryVar in neededQueryCopy)
            {
                if (string.Compare(parameterName, queryVar, StringComparison.OrdinalIgnoreCase) == 0)
                {
                    if (!qsc.CanConvert(mpd.Type))
                    {
                        throw new InvalidOperationException();
                    }
                    queryMapping.Add(i, new KeyValuePair<string, Type>(parameterName, mpd.Type));
                    alreadyGotVars.Add(parameterName, 0);
                    neededQueryVars.Remove(queryVar);
                }
            }
        }
        if (neededPathVars.Count != 0)
        {
            throw new InvalidOperationException();
        }
        if (neededQueryVars.Count != 0)
        {
            throw new InvalidOperationException();
        }
    }
    private static string GetUTStringOrDefault(OperationDescription operationDescription)
    {
        string utString = GetWebUriTemplate(operationDescription);
        if (utString == null && GetWebMethod(operationDescription) == "GET")
        {
            utString = MakeDefaultGetUTString(operationDescription);
        }
        if (utString == null)
        {
            utString = operationDescription.Name;
        }
        return utString;
    }
    private static string MakeDefaultGetUTString(OperationDescription od)
    {
        StringBuilder sb = new StringBuilder(XmlConvert.DecodeName(od.Name));
        //sb.Append("/*"); // note: not + "/*", see 8988 and 9653
        if (!IsUntypedMessage(od.Messages[0]))
        {
            sb.Append("?");
            foreach (MessagePartDescription mpd in od.Messages[0].Body.Parts)
            {
                string parameterName = XmlConvert.DecodeName(mpd.Name);
                sb.Append(parameterName);
                sb.Append("={");
                sb.Append(parameterName);
                sb.Append("}&");
            }
            sb.Remove(sb.Length - 1, 1);
        }
        return sb.ToString();
    }
    private static bool IsUntypedMessage(MessageDescription message)
    {

        if (message == null)
        {
            return false;
        }
        return (message.Body.ReturnValue != null && message.Body.Parts.Count == 0 && message.Body.ReturnValue.Type == typeof(Message)) ||
            (message.Body.ReturnValue == null && message.Body.Parts.Count == 1 && message.Body.Parts[0].Type == typeof(Message));
    }
    private static void EnsureOk(WebGetAttribute wga, WebInvokeAttribute wia, OperationDescription od)
    {
        if (wga != null && wia != null)
        {
            throw new InvalidOperationException();
        }
    }
    private static string GetWebUriTemplate(OperationDescription od)
    {
        // return exactly what is on the attribute
        WebGetAttribute wga = od.Behaviors.Find<WebGetAttribute>();
        WebInvokeAttribute wia = od.Behaviors.Find<WebInvokeAttribute>();
        EnsureOk(wga, wia, od);
        if (wga != null)
        {
            return wga.UriTemplate;
        }
        else if (wia != null)
        {
            return wia.UriTemplate;
        }
        else
        {
            return null;
        }
    }
    private static string GetWebMethod(OperationDescription od)
    {
        WebGetAttribute wga = od.Behaviors.Find<WebGetAttribute>();
        WebInvokeAttribute wia = od.Behaviors.Find<WebInvokeAttribute>();
        EnsureOk(wga, wia, od);
        if (wga != null)
        {
            return "GET";
        }
        else if (wia != null)
        {
            return wia.Method ?? "POST";
        }
        else
        {
            return "POST";
        }
    }

}

以及以下行为:

class NewtonsoftJsonBehavior : WebHttpBehavior
{
    protected override IDispatchMessageFormatter GetRequestDispatchFormatter(OperationDescription operationDescription, ServiceEndpoint endpoint)
    {
        return new UriTemplateDispatchFormatter(
            operationDescription,
            new NewtonsoftJsonDispatchFormatter(operationDescription, endpoint, true),
            GetQueryStringConverter(operationDescription),
            endpoint.Contract.Name,
            endpoint.Address.Uri);
    }

    protected override IDispatchMessageFormatter GetReplyDispatchFormatter(OperationDescription od, ServiceEndpoint ep)
    {
        return new NewtonsoftJsonDispatchFormatter(od, ep, false);
    }

}

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