WCF 第十三章 可编程站点 使用WebOperationContext

寄宿服务使用WebHttpinding绑定来读或者写HTTP上下文是很常见的。这可以使用WebOperationContext类实现。有很多理由来访问HTTP上下文。你可能想要读取自定义的认证信息头或授权信息头，控制缓存或者设置内容类型，例如。

  图片13.3 显示了一个在当前计算机上显示墙纸的网络应用程序。整个应用程序是使用一个WCF服务创建的而且可以使用网络浏览器访问。

图片13.3 墙纸网络应用程序

 

  图片13.12显示了WallpaperService服务的代码。有一个在一个HTML页上显示所有图片的Images操作。这个操作设置ContextType头以便于浏览器可以将输入理解成HTML。它也设置了Cache-Control头以便于额外的图片可以添加到应用程序中而不用浏览器缓存图像。最后，有一个将一个图像返回给浏览器的Image操作。这个操作设置ContextType和ETag头。

注意 从REST中获得.svc
WCF服务使用.svc扩展在IIS中寄宿。这和常见的REST URI 命名经验不同。例如，列表13.12中的服务使如下URI访问:http://localhost/Wallpaper/WallpaperService.svc/images  
你可以通过使用一个ASP.NET HttpModule(仅IIS 7.0)调用HttpContext.RewritePath去修改URI来移除.svc扩展名。这将允许URI采用下面格式: http://localhost/Wallpaper/WallpaperService/images

列表13.12 Wallpaper图片服务

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using System;

using System.Collections.Generic;

using System.Linq;

using System.Runtime.Serialization;

using System.ServiceModel;

using System.ServiceModel.Web;

using System.Text;

using System.ServiceModel.Activation;

using System.Web;

using System.IO;

using System.Web.UI;

 

namespace EssentialWCF.WallpaperImage

{

    // NOTE: You can use the "Rename" command on the "Refactor" menu to change the interface name "IService1" in both code and config file together.

    [ServiceContract]

    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Required)]

    public class WallpaperService

    {

        private static UriTemplate ImageUriTemplate =

            new UriTemplate("/image/{name}");

 

        private string ImagePath

        {

            get

            {

                return @"C:\Windows\Web\Wallpaper";

            }

        }

 

        private Image GetImage(string name, Uri baseUri)

        {

            return new Image(name, ImageUriTemplate.BindByPosition(baseUri, new string[] { name }));

        }

 

        private void PopulateListOfImages(List<Image> list, Uri baseUri)

        {

            HttpContext ctx = HttpContext.Current; ;

            DirectoryInfo d = new DirectoryInfo(ImagePath);

            FileInfo[] files = d.GetFiles("*.jpg");

 

            foreach (FileInfo f in files)

            {

                string fileName = f.Name.Split(new char[] { '.' })[0];

                string etag = fileName + "_" + f.LastWriteTime.ToString();

                list.Add(GetImage(fileName, baseUri));

            }

        }

 

        [OperationContract]

        [WebGet(UriTemplate = "/images")]

        public void Images()

        {

            WebOperationContext wctx = WebOperationContext.Current; ;

 

            wctx.OutgoingResponse.ContentType = "text/html";

            wctx.OutgoingResponse.Headers.Add("Cache-Control", "no-cache");

 

            Uri baseUri = wctx.IncomingRequest.UriTemplateMatch.BaseUri;

            List<Image> listOfImages = new List<Image>();

            PopulateListOfImages(listOfImages, baseUri);

 

            TextWriter sw = new StringWriter(); ;

            Html32TextWriter htmlWriter = new Html32TextWriter(sw);

 

            htmlWriter.WriteFullBeginTag("HTML");

            htmlWriter.WriteFullBeginTag("BODY");

            htmlWriter.WriteFullBeginTag("H1");

            htmlWriter.Write("wallpaper");

            htmlWriter.WriteEndTag("H1");

            htmlWriter.WriteFullBeginTag("TABLE");

            htmlWriter.WriteFullBeginTag("TR");

 

            int i = 0;

 

            Image image;

            while (i < listOfImages.Count)

            {

                image = listOfImages[i];

 

                htmlWriter.WriteFullBeginTag("TD");

                htmlWriter.Write(image.Name);

                htmlWriter.WriteBreak();

                htmlWriter.WriteBeginTag("IMG");

                htmlWriter.WriteAttribute("SRC", image.Uri);

                htmlWriter.WriteAttribute("STYLE", "width:150px;height:150px");

                htmlWriter.WriteEndTag("IMG");

                htmlWriter.WriteEndTag("TD");

 

                if (((i + 1) % 5) == 0)

                {

                    htmlWriter.WriteEndTag("TR");

                    htmlWriter.WriteFullBeginTag("TR");

                }

                i++;

            }

            htmlWriter.WriteEndTag("TR");

            htmlWriter.WriteEndTag("TABLE");

            htmlWriter.WriteEndTag("BODY");

            htmlWriter.WriteEndTag("HTML");

 

            HttpContext ctx = HttpContext.Current;

            ctx.Response.Write(sw.ToString());

        }

 

        [OperationContract]

        [WebGet(UriTemplate = "/image/{name}")]

        public void GetImage(string name)

        {

            WebOperationContext wctx = WebOperationContext.Current;

            wctx.OutgoingResponse.ContentType = "image/jpeg";

 

            HttpContext ctx = HttpContext.Current;

 

            string fileName = null;

            byte[] fileBytes = null;

            try

            {

                fileName = string.Format(@"{0}\{1}.jpg", ImagePath, name);

                if (File.Exists(fileName))

                {

                    using(FileStream fs = File.OpenRead(fileName))

                    {

                        fileBytes = new byte[fs.Length];

                        fs.Read(fileBytes, 0, Convert.ToInt32(fs.Length));

                    }

                }

                else

                {

                    wctx.OutgoingResponse.StatusCode = System.Net.HttpStatusCode.NotFound;

                }

            }

            catch

            {

                wctx.OutgoingResponse.StatusCode = System.Net.HttpStatusCode.NotFound;

            }

 

            FileInfo fi = new FileInfo(fileName);

            wctx.OutgoingResponse.ETag = fileName + "_" + fi.LastWriteTime.ToString();

            ctx.Response.OutputStream.Write(fileBytes, 0, fileBytes.Length);

        }

    }

    // Use a data contract as illustrated in the sample below to add composite types to service operations.

    [DataContract]

    public class Image

    {

        string name;

        string uri;

 

        public Image()

        {

        }

 

        public Image(string name, string uri)

        {

            this.name = name;

            this.uri = uri;

        }

 

        public Image(string name, Uri uri)

        {

            this.name = name;

            this.uri = uri.ToString();

        }

 

        [DataMember]

        public string Name

        {

            get { return this.name; }

            set { this.name = value; }

        }

 

        [DataMember]

        public string Uri

        {

            get { return this.uri; }

            set { this.uri = value; }

        }

    }

}

 

  下面列表13.13中的配置用来寄宿WallpaperService服务。服务使用WebHttpBinding绑定和WebHttpBehavior终结点行为来寄宿。

列表13.13 Wallpaper图像服务配置

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<system.serviceModel>

      <serviceHostingEnvironment aspNetCompatibilityEnabled="true"/>

      <services>

          <service name="EssentialWCF.WallpaperImage.WallpaperService"

             behaviorConfiguration="MetadataBehavior">

              <endpoint address=""

                behaviorConfiguration="WebBehavior"

                binding="webHttpBinding"

                contract="EssentialWCF.WallpaperImage.WallpaperService"/>

              <endpoint address="mex"

                binding="mexHttpBinding"

                contract="IMetadataExchange"/>

          </service>

      </services>

      <behaviors>

          <endpointBehaviors>

              <behavior name="WebBehavior">

                  <webHttp/>

              </behavior>

          </endpointBehaviors>

          <serviceBehaviors>

              <behavior name="MetadataBehavior">

                  <serviceMetadata httpGetEnabled="true" httpGetUrl=""/>

                  <serviceDebug includeExceptionDetailInFaults="true"/>

              </behavior>

          </serviceBehaviors>

      </behaviors>

  </system.serviceModel>

  列表13.14 显示了用来在IIS中寄宿WallpaperService的.svc文件。

列表13.14 WallpaperService.svc

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<%@ ServiceHost Language="C#" Debug="true"

Service="EssentialWCF.WallpaperImage.WallpaperService"

CodeBehind="~/App_Code/WallpaperImageService.cs" %>