Procedimiento para exponer una fuente como Atom y RSS

Windows Communication Foundation (WCF) le permite crear un servicio que expone una fuente de redifusión. En este tema se explica cómo crear un servicio de distribución que exponga una fuente de distribución mediante Atom 1.0 y RSS 2.0. Este servicio expone un punto de conexión que puede devolver cualquiera de los dos formatos de distribución. Para simplificar, el servicio usado en este ejemplo tiene host propio. En un entorno de producción un servicio de este tipo estaría hospedado en IIS o WAS. Para más información sobre las diferentes opciones de hospedaje de WCF, consulte Hospedaje.

Creación de un servicio de distribución básico

1. Defina un contrato de servicios utilizando una interfaz marcada con el atributo WebGetAttribute. Cada operación que se expone como una fuente de distribución devuelve un objeto SyndicationFeedFormatter. Observe los parámetros de WebGetAttribute. UriTemplate especifica la dirección URL usada para invocar esta operación de servicio. La cadena de este parámetro contiene literales y una variable entre llaves ({format}). Esta variable corresponde al parámetro format de la operación del servicio. Para obtener más información, vea UriTemplate. BodyStyle afecta a cómo se escriben los mensajes que esta operación de servicio envía y recibe. Bare especifica que los datos enviados a y desde esta operación de servicio no están ajustados por los elementos XML definidos por la infraestructura. Para obtener más información, vea WebMessageBodyStyle.

   [ServiceContract]
   [ServiceKnownType(typeof(Atom10FeedFormatter))]
   [ServiceKnownType(typeof(Rss20FeedFormatter))]
   public interface IBlog
   {
       [OperationContract]
       [WebGet(UriTemplate = "GetBlog?format={format}")]
       SyndicationFeedFormatter GetBlog(string format);
   }
   

   <ServiceContract()> _
   <ServiceKnownType(GetType(Atom10FeedFormatter))> _
   <ServiceKnownType(GetType(Rss20FeedFormatter))> _
   Public Interface IBlog
       <OperationContract()> _
       <WebGet(UriTemplate:="GetBlog?format={format}")> _
       Function GetBlog(ByVal format As String) As SyndicationFeedFormatter
   End Interface
   

   Nota

   Utilice el ServiceKnownTypeAttribute para especificar los tipos que devuelven las operaciones de servicio en esta interfaz.

2. Implemente el contrato de servicios.

   public class BlogService : IBlog
   {
       public SyndicationFeedFormatter GetBlog(string format)
       {
           SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
           feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
           feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
           feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
           SyndicationItem item1 = new SyndicationItem(
               "Item One",
               "This is the content for item one",
               new Uri("http://localhost/Content/One"),
               "ItemOneID",
               DateTime.Now);
   
           SyndicationItem item2 = new SyndicationItem(
               "Item Two",
               "This is the content for item two",
               new Uri("http://localhost/Content/Two"),
               "ItemTwoID",
               DateTime.Now);
   
           SyndicationItem item3 = new SyndicationItem(
               "Item Three",
               "This is the content for item three",
               new Uri("http://localhost/Content/three"),
               "ItemThreeID",
               DateTime.Now);
           List<SyndicationItem> items = new List<SyndicationItem>();
           items.Add(item1);
           items.Add(item2);
           items.Add(item3);
   
           feed.Items = items;
   
           if (format == "rss")
               return new Rss20FeedFormatter(feed);
           else if (format == "atom")
               return new Atom10FeedFormatter(feed);
           else return null;
       }
   }
   

   Public Class BlogService
       implements IBlog
   
       Public Function GetBlog(ByVal format As String) As SyndicationFeedFormatter Implements IBlog.GetBlog
           Dim feed As New SyndicationFeed("My Blog Feed", "This is a test feed", New Uri("http://SomeURI"))
           feed.Authors.Add(New SyndicationPerson("someone@microsoft.com"))
           feed.Categories.Add(New SyndicationCategory("How To Sample Code"))
           feed.Description = New TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF")
           Dim item1 As New SyndicationItem( _
               "Item One", _
               "This is the content for item one", _
               New Uri("http://localhost/Content/One"), _
               "ItemOneID", _
               DateTime.Now)
   
           Dim item2 As New SyndicationItem( _
               "Item Two", _
               "This is the content for item two", _
               New Uri("http://localhost/Content/Two"), _
               "ItemTwoID", _
               DateTime.Now)
   
           Dim item3 As New SyndicationItem( _
               "Item Three", _
               "This is the content for item three", _
               New Uri("http://localhost/Content/three"), _
               "ItemThreeID", _
               DateTime.Now)
           Dim items As New List(Of SyndicationItem)()
           items.Add(item1)
           items.Add(item2)
           items.Add(item3)
   
           feed.Items = items
   
           If (format = "rss") Then
               Return New Rss20FeedFormatter(feed)
           Else
               Return New Atom10FeedFormatter(feed)
           End If
       End Function
   End Class
   

3. Cree un objeto SyndicationFeed y agregue un autor, categoría y descripción.

   SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
   feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
   feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
   feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
   

   Dim feed As New SyndicationFeed("My Blog Feed", "This is a test feed", New Uri("http://SomeURI"))
   feed.Authors.Add(New SyndicationPerson("someone@microsoft.com"))
   feed.Categories.Add(New SyndicationCategory("How To Sample Code"))
   feed.Description = New TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF")
   

4. Cree varios objetos SyndicationItem.

   SyndicationItem item1 = new SyndicationItem(
       "Item One",
       "This is the content for item one",
       new Uri("http://localhost/Content/One"),
       "ItemOneID",
       DateTime.Now);
   
   SyndicationItem item2 = new SyndicationItem(
       "Item Two",
       "This is the content for item two",
       new Uri("http://localhost/Content/Two"),
       "ItemTwoID",
       DateTime.Now);
   
   SyndicationItem item3 = new SyndicationItem(
       "Item Three",
       "This is the content for item three",
       new Uri("http://localhost/Content/three"),
       "ItemThreeID",
       DateTime.Now);
   

   Dim item1 As New SyndicationItem( _
       "Item One", _
       "This is the content for item one", _
       New Uri("http://localhost/Content/One"), _
       "ItemOneID", _
       DateTime.Now)
   
   Dim item2 As New SyndicationItem( _
       "Item Two", _
       "This is the content for item two", _
       New Uri("http://localhost/Content/Two"), _
       "ItemTwoID", _
       DateTime.Now)
   
   Dim item3 As New SyndicationItem( _
       "Item Three", _
       "This is the content for item three", _
       New Uri("http://localhost/Content/three"), _
       "ItemThreeID", _
       DateTime.Now)
   

5. Agregue los objetos SyndicationItem a la fuente.

   List<SyndicationItem> items = new List<SyndicationItem>();
   items.Add(item1);
   items.Add(item2);
   items.Add(item3);
   
   feed.Items = items;
   

   Dim items As New List(Of SyndicationItem)()
   items.Add(item1)
   items.Add(item2)
   items.Add(item3)
   
   feed.Items = items
   

6. Utilice el parámetro format para devolver el formato solicitado.

   if (format == "rss")
       return new Rss20FeedFormatter(feed);
   else if (format == "atom")
       return new Atom10FeedFormatter(feed);
   else return null;
   

   If (format = "rss") Then
       Return New Rss20FeedFormatter(feed)
   Else
       Return New Atom10FeedFormatter(feed)
   End If
   

Para hospedar el servicio

1. Crear un objeto WebServiceHost. La clase WebServiceHost agrega automáticamente un punto de conexión en la dirección base del servicio, salvo que se especifique uno en el código o en la configuración. En este ejemplo, no se especifica ningún punto de conexión, por lo que se expone el predeterminado.

   Uri address = new Uri("http://localhost:8000/BlogService/");
   WebServiceHost svcHost = new WebServiceHost(typeof(BlogService), address);
   

   Dim address As New Uri("http://localhost:8000/BlogService/")
   Dim svcHost As New WebServiceHost(GetType(BlogService), address)
   

2. Abra el host de servicio, cargue la fuente desde el servicio, muestre la fuente y espere a que el usuario presione Entrar.

   svcHost.Open();
   Console.WriteLine("Service is running");
   
   Console.WriteLine("Loading feed in Atom 1.0 format.");
   XmlReader atomReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
   SyndicationFeed atomFeed = SyndicationFeed.Load(atomReader);
   Console.WriteLine(atomFeed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in atomFeed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
   }
   
   Console.WriteLine("Loading feed in RSS 2.0 format.");
   XmlReader rssReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss");
   SyndicationFeed rssFeed = SyndicationFeed.Load(rssReader);
   Console.WriteLine(rssFeed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in rssFeed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       // Notice we are using item.Summary here instead of item.Content. This is because
       // of the differences between Atom 1.0 and RSS 2.0 specs.
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Summary).Text);
   }
   
   Console.WriteLine("Press <ENTER> to quit...");
   Console.ReadLine();
   svcHost.Close();
   

   svcHost.Open()
   Console.WriteLine("Service is running")
   
   Console.WriteLine("Loading feed in Atom 1.0 format.")
   Dim atomReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom")
   Dim atomFeed As SyndicationFeed = SyndicationFeed.Load(atomReader)
   Console.WriteLine(atomFeed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In atomFeed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", CType(item.Content, TextSyndicationContent).Text)
   Next
   
   Console.WriteLine("Loading feed in RSS 2.0 format.")
   Dim rssReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss")
   Dim rssFeed As SyndicationFeed = SyndicationFeed.Load(rssReader)
   Console.WriteLine(rssFeed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In rssFeed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", CType(item.Content, TextSyndicationContent).Text)
   Next
   
   
   Console.WriteLine("Press <ENTER> to quit...")
   Console.ReadLine()
   svcHost.Close()
   

Llamar a GetBlog mediante HTTP GET

1. Abra un explorador, escriba la siguiente dirección URL y presione Entrar: http://localhost:8000/BlogService/GetBlog.

   La URL contiene la dirección base del servicio (http://localhost:8000/BlogService), la dirección relativa del punto de conexión y la operación del servicio que se va a llamar.

Llamar a GetBlog() mediante código

1. Cree un XmlReader con la dirección base y el método al que está llamando.

   XmlReader reader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
   

   Dim atomReader As XmlReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom")
   

2. Llame al método estático Load(XmlReader), pasando el XmlReader que acaba de crear.

   SyndicationFeed feed = SyndicationFeed.Load(reader);
   

   Dim feed As SyndicationFeed = SyndicationFeed.Load(atomReader)
   

   Esto invoca la operación de servicio y rellena una nueva SyndicationFeed con el formateador devuelto desde la operación del servicio.

3. Obtenga acceso al objeto de fuente.

   Console.WriteLine(feed.Title.Text);
   Console.WriteLine("Items:");
   foreach (SyndicationItem item in feed.Items)
   {
       Console.WriteLine("Title: {0}", item.Title.Text);
       Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
   }
   

   Console.WriteLine(feed.Title.Text)
   Console.WriteLine("Items:")
   For Each item As SyndicationItem In feed.Items
       Console.WriteLine("Title: {0}", item.Title.Text)
       Console.WriteLine("Content: {0}", (CType(item.Content, TextSyndicationContent).Text))
   Next
   

Ejemplo

A continuación, se muestra una lista de código completa para este ejemplo.

using System;
using System.Xml;
using System.Collections.Generic;
using System.ServiceModel;
using System.ServiceModel.Description;
using System.ServiceModel.Syndication;
using System.ServiceModel.Web;
namespace Service
{
    [ServiceContract]
    [ServiceKnownType(typeof(Atom10FeedFormatter))]
    [ServiceKnownType(typeof(Rss20FeedFormatter))]
    public interface IBlog
    {
        [OperationContract]
        [WebGet(UriTemplate = "GetBlog?format={format}")]
        SyndicationFeedFormatter GetBlog(string format);
    }

    public class BlogService : IBlog
    {
        public SyndicationFeedFormatter GetBlog(string format)
        {
            SyndicationFeed feed = new SyndicationFeed("My Blog Feed", "This is a test feed", new Uri("http://SomeURI"));
            feed.Authors.Add(new SyndicationPerson("someone@microsoft.com"));
            feed.Categories.Add(new SyndicationCategory("How To Sample Code"));
            feed.Description = new TextSyndicationContent("This is a sample that demonstrates how to expose a feed through RSS and Atom with WCF");
            SyndicationItem item1 = new SyndicationItem(
                "Item One",
                "This is the content for item one",
                new Uri("http://localhost/Content/One"),
                "ItemOneID",
                DateTime.Now);

            SyndicationItem item2 = new SyndicationItem(
                "Item Two",
                "This is the content for item two",
                new Uri("http://localhost/Content/Two"),
                "ItemTwoID",
                DateTime.Now);

            SyndicationItem item3 = new SyndicationItem(
                "Item Three",
                "This is the content for item three",
                new Uri("http://localhost/Content/three"),
                "ItemThreeID",
                DateTime.Now);
            List<SyndicationItem> items = new List<SyndicationItem>();
            items.Add(item1);
            items.Add(item2);
            items.Add(item3);

            feed.Items = items;

            if (format == "rss")
                return new Rss20FeedFormatter(feed);
            else if (format == "atom")
                return new Atom10FeedFormatter(feed);
            else return null;
        }
    }

    public class Host
    {
        static void Main(string[] args)
        {
            Uri address = new Uri("http://localhost:8000/BlogService/");
            WebServiceHost svcHost = new WebServiceHost(typeof(BlogService), address);
            try
            {
                svcHost.Open();
                Console.WriteLine("Service is running");

                Console.WriteLine("Loading feed in Atom 1.0 format.");
                XmlReader atomReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=atom");
                SyndicationFeed atomFeed = SyndicationFeed.Load(atomReader);
                Console.WriteLine(atomFeed.Title.Text);
                Console.WriteLine("Items:");
                foreach (SyndicationItem item in atomFeed.Items)
                {
                    Console.WriteLine("Title: {0}", item.Title.Text);
                    Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Content).Text);
                }

                Console.WriteLine("Loading feed in RSS 2.0 format.");
                XmlReader rssReader = XmlReader.Create("http://localhost:8000/BlogService/GetBlog?format=rss");
                SyndicationFeed rssFeed = SyndicationFeed.Load(rssReader);
                Console.WriteLine(rssFeed.Title.Text);
                Console.WriteLine("Items:");
                foreach (SyndicationItem item in rssFeed.Items)
                {
                    Console.WriteLine("Title: {0}", item.Title.Text);
                    // Notice we are using item.Summary here instead of item.Content. This is because
                    // of the differences between Atom 1.0 and RSS 2.0 specs.
                    Console.WriteLine("Content: {0}", ((TextSyndicationContent)item.Summary).Text);
                }

                Console.WriteLine("Press <ENTER> to quit...");
                Console.ReadLine();
                svcHost.Close();
            }
            catch (CommunicationException ce)
            {
                Console.WriteLine("An exception occurred: {0}", ce.Message);
                svcHost.Abort();
            }
        }
    }
}

Compilar el código

Al compilar el código anterior, haga referencia a System.ServiceModel.dll y System.ServiceModel.Web.dll.

Consulte también

• WebHttpBinding
• WebGetAttribute