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

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

  <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

<%@ ServiceHost Language="C#" Debug="true" 
Service="EssentialWCF.WallpaperImage.WallpaperService" 
CodeBehind="~/App_Code/WallpaperImageService.cs" %>