Gör så här: Exponera ett flöde som både Atom och RSS

Artikel
03/02/2024

Med Windows Communication Foundation (WCF) kan du skapa en tjänst som exponerar ett syndikeringsflöde. I det här avsnittet beskrivs hur du skapar en syndikeringstjänst som exponerar ett syndikeringsflöde med både Atom 1.0 och RSS 2.0. Den här tjänsten exponerar en slutpunkt som kan returnera antingen syndikeringsformat. För enkelhetens skull är tjänsten som används i det här exemplet egen värd. I en produktionsmiljö finns en tjänst av den här typen under IIS eller WAS. Mer information om de olika WCF-värdalternativen finns i Värd.

Skapa en grundläggande syndikeringstjänst

Definiera ett tjänstkontrakt med hjälp av ett gränssnitt som markerats med attributet WebGetAttribute . Varje åtgärd som exponeras som en syndikeringsfeed returnerar ett SyndicationFeedFormatter objekt. Observera parametrarna WebGetAttributeför . UriTemplate anger den URL som används för att anropa den här tjänståtgärden. Strängen för den här parametern innehåller literaler och en variabel i klammerparenteser ({format}). Den här variabeln motsvarar tjänståtgärdens format parameter. Mer information finns i UriTemplate. BodyStyle påverkar hur meddelanden som den här tjänståtgärden skickar och tar emot skrivs. Bare anger att de data som skickas till och från den här tjänståtgärden inte omsluts av infrastrukturdefinierade XML-element. Mer information finns i 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
```
Kommentar

ServiceKnownTypeAttribute Använd för att ange vilka typer som returneras av tjänståtgärderna i det här gränssnittet.

Implementera tjänstkontraktet.

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

Skapa ett SyndicationFeed objekt och lägg till en författare, kategori och beskrivning.

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")

Skapa flera SyndicationItem objekt.

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)

Lägg till objekten i SyndicationItem feeden.

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

Använd formatparametern för att returnera det begärda formatet.

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

Värd för tjänsten

Skapa ett WebServiceHost objekt. Klassen WebServiceHost lägger automatiskt till en slutpunkt på tjänstens basadress såvida inte en anges i kod eller konfiguration. I det här exemplet anges inga slutpunkter så att standardslutpunkten exponeras.

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)

Öppna tjänstvärden, läs in feeden från tjänsten, visa feeden och vänta tills användaren trycker på RETUR.

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()

Så här anropar du GetBlog med en HTTP GET

Öppna en webbläsare, ange följande URL och tryck på Retur: http://localhost:8000/BlogService/GetBlog.

URL:en innehåller basadressen för tjänsten (http://localhost:8000/BlogService), slutpunktens relativa adress och den tjänståtgärd som ska anropas.

Anropa GetBlog() från kod

Skapa en XmlReader med basadressen och den metod som du anropar.

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

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

Anropa den statiska Load(XmlReader) metoden och skicka in den XmlReader du nyss skapade.
```
SyndicationFeed feed = SyndicationFeed.Load(reader);
```
```
Dim feed As SyndicationFeed = SyndicationFeed.Load(atomReader)
```
Detta anropar tjänståtgärden och fyller i en ny SyndicationFeed med formateren som returneras från tjänståtgärden.

Få åtkomst till feedobjektet.

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

Exempel

Följande är den fullständiga kodlistan för det här exemplet.

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();
            }
        }
    }
}

Kompilera koden

När du kompilerar föregående kod refererar du till System.ServiceModel.dll och System.ServiceModel.Web.dll.

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