WCF REST 服务流式传输 JSON 对象

Posted 2023-05-07

【中文标题】WCF REST 服务流式传输 JSON 对象

【英文标题】：WCF REST service streaming JSON objects

【发布时间】：2021-06-16 16:25:19

【问题描述】：

我需要一个 Windows 服务，其中 REST API 将一堆 JSON 对象转储到一个流中（内容类型：application/stream+json）。

示例响应（不是对象数组）：

 id: 1, name: "name 1" 
 id: 2, name: "name 2" 
 id: 3, name: "name 3" 
 id: 4, name: "name 4" 

可以在 WCF REST 中执行此操作吗？或者我应该尝试其他方法？

【问题讨论】：

docs.microsoft.com/en-us/dotnet/framework/wcf/feature-details/…

【参考方案1】：

几天后，我找到了解决方案。首先，我修改了 App.config 文件并将绑定配置添加到允许流式响应的端点。接下来，服务合约的操作必须有返回流。然后在服务合同的实施中，我将传出响应内容类型设置为“application/stream+json”，使用 DataContractJsonSerializer 序列化所有对象并写入 MemoryStream。最后，我将 MemoryStream 的位置设置为零，然后返回该流。

示例代码如下。

App.config：

<system.serviceModel>
  <serviceHostingEnvironment aspNetCompatibilityEnabled="true" />
  <services>
    <service name="WinService.WcfService">
      <endpoint address="" binding="webHttpBinding" bindingConfiguration="webHttpBindingStreamedResponse" contract="WinService.IWcfService" behaviorConfiguration="webHttp" />
      <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" />
    </service>
  </services>
  <bindings>
    <webHttpBinding>
      <binding name="webHttpBindingStreamedResponse" transferMode="StreamedResponse" maxReceivedMessageSize="67108864"/>
    </webHttpBinding>
  </bindings>
  <behaviors>
    <serviceBehaviors>
      <behavior>
        <!-- To avoid disclosing metadata information, 
        set the values below to false before deployment -->
        <serviceMetadata httpGetEnabled="True" httpsGetEnabled="True" />
        <!-- To receive exception details in faults for debugging purposes, 
        set the value below to true.  Set to false before deployment 
        to avoid disclosing exception information -->
        <serviceDebug includeExceptionDetailInFaults="True" />
      </behavior>
    </serviceBehaviors>
    <endpointBehaviors>
      <behavior name="webHttp">
        <webHttp />
      </behavior>
    </endpointBehaviors>
  </behaviors>
</system.serviceModel>

服务合同：

[ServiceContract]
public interface IWcfService

  [OperationContract]
  [WebGet(UriTemplate = "/stream/param", ResponseFormat = WebMessageFormat.Json)]
  Stream GetJsonStreamedObjects(string param);

ServiceContract的实现：

[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class WcfService : IWcfService

  public Stream GetJsonStreamedObjects(string param)
  
    var stream = new MemoryStream();
    var serializer = new DataContractJsonSerializer(typeof(JsonObjectDataContract));

    WebOperationContext.Current.OutgoingResponse.ContentType = "application/stream+json";

    foreach (JsonObjectDataContract jsonObjectDataContract in Repository.GetJsonObjectDataContracts(param))
    
      serializer.WriteObject(stream, jsonObjectDataContract);
    
    stream.Position = 0;
    return stream;