yahoo OPEN api测试之weather feed -

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yahoo OPEN api测试之weather feed

昨天写了个google的feed api应用,突然对rss蛮感兴趣的,天生比较好奇,以前都是做windows程序感觉进入互联网领域,象是走进另外一扇大门,更加有趣,更加丰富多彩.先展示一下结果
 <img src="http://p.blog.csdn.net/images/p_blog_csdn_net/linkyou/EntryImages/20090227/Snap1.gif" alt="" width="370" height="547">
 调用feed api最主要要学习的知识是RSS读取的问题.
 .NET框架提供了<a href="http://msdn.microsoft.com/zh-cn/library/system.xml.serialization.xmlserializer.aspx" target="_blank">System.Xml.Serialization.XmlSerializer类型</a>，为将对象序列化为XML或将XML序列化为对象提供了很大支持。
 下面我们针对yahoo weather feed api,通过实例讲解一下如何读取RSS文件。
 首先通过yahoo weather feed api
 "http://xml.weather.yahoo.com/forecastrss?p=" & p & "&u=" & U
 可以得到如下RSS文件
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<rss version="2.0" xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#">
 <channel>
 <title>Yahoo! Weather - Hangzhou, CH</title>
 <link>http://us.rd.yahoo.com/dailynews/rss/weather/Hangzhou__CH/*http://weather.yahoo.com/forecast/CHXX0044_f.html</link>
 <description>Yahoo! Weather for Hangzhou, CH</description>
 <language>en-us</language>
 <lastBuildDate>Fri, 27 Feb 2009 12:30 pm CST</lastBuildDate>
 <ttl>60</ttl>
 <yweather:location city="Hangzhou" region="" country="CH" />
 <yweather:units temperature="F" distance="mi" pressure="in" speed="mph" />
 <yweather:wind chill="39" direction="20" speed="7" />
 <yweather:atmosphere humidity="81" visibility="1.86" pressure="30.27" rising="0" />
 <yweather:astronomy sunrise="6:28 am" sunset="5:57 pm" />
 <image>
 <title>Yahoo! Weather</title>
 <width>142</width>
 <height>18</height>
 <link>http://weather.yahoo.com</link>
 <url>http://l.yimg.com/a/i/us/nws/th/main_142b.gif</url>
 </image>
 <item>
 <title>Conditions for Hangzhou, CH at 12:30 pm CST</title>
 <geo:lat>30.23</geo:lat>
 <geo:long>120.17</geo:long>
 <link>http://us.rd.yahoo.com/dailynews/rss/weather/Hangzhou__CH/*http://weather.yahoo.com/forecast/CHXX0044_f.html</link>
 <pubDate>Fri, 27 Feb 2009 12:30 pm CST</pubDate>
 <yweather:condition text="Rain Shower" code="11" temp="43" date="Fri, 27 Feb 2009 12:30 pm CST" />
 <description>
 <![CDATA[
 <img src="http://l.yimg.com/a/i/us/we/52/11.gif"/>
 
 Current Conditions:
 
 Rain Shower, 43 F 
 
 Forecast:
 
 Fri - Rain. High: 42 Low: 39 
 Sat - Rain. High: 43 Low: 40 
 
 <a href="http://us.rd.yahoo.com/dailynews/rss/weather/Hangzhou__CH/*http://weather.yahoo.com/forecast/CHXX0044_f.html">Full Forecast at Yahoo! Weather</a>
 
 (provided by The Weather Channel) 
 ]]>
 </description>
 <yweather:forecast day="Fri" date="27 Feb 2009" low="39" high="42" text="Rain" code="12" />
 <yweather:forecast day="Sat" date="28 Feb 2009" low="40" high="43" text="Rain" code="12" />
 <guid isPermaLink="false">CHXX0044_2009_02_27_12_30_CST</guid>
 </item>
 </channel>
</rss>


</td>
</tr></tbody></table>

如上文所说.NET框架提供了<a href="http://msdn.microsoft.com/zh-cn/library/system.xml.serialization.xmlserializer.aspx" target="_blank">System.Xml.Serialization.XmlSerializer类型</a>，现在我们要做的就是如何利用xmlSerializer将XML序列化为对象。
 对于上面的XML文件为了便于对象序列化我们会做如下替换
 
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
 str = str.Replace("yweather:", "")
 str = str.Replace("geo:", "")
 'Dim str1 As String = """ : "

 Dim str1 = "isPermaLink=""false"""
 str = str.Replace(str1, "")
 str1 = " version=""2.0"" xmlns:yweather=""http://xml.weather.yahoo.com/ns/rss/1.0"" xmlns:geo=""http://www.w3.org/2003/01/geo/wgs84_pos#"""
 str = str.Replace(str1, "")
</td>
</tr></tbody></table>

接着我们需要按照xml的格式，将所有的节点定义为对象，并将节点的属性定义为对象的属性。
 如该RSS中需要先定义rss对象
 
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
Imports Microsoft.VisualBasic
Imports System.Xml.Serialization
Partial Class YahooWeatherForecast

 <XmlRoot("rss")> _
 Public Class rssClass
 Private _channel As channelClass

 <XmlElement()> _
 Public Property channel() As channelClass
 Get
 Return _channel
 End Get
 Set(ByVal value As channelClass)
 _channel = value
 End Set
 End Property
 End Class
End Class
</td>
</tr></tbody></table>
在该对象中包含chanelClass，保持和xml的文件相同的结构
接下来我们需要定义chanelClass,代码如下:
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
Imports Microsoft.VisualBasic
Imports System.Xml.Serialization
Partial Class YahooWeatherForecast
 Partial Class rssClass
 Partial Class channelClass
 Private _title As String
 ''' <summary>
 ''' The title of the feed, which includes the location city. For example "Yahoo! Weather - Sunnyvale, CA" 
 ''' </summary>
 <XmlElement()> _
 Public Property title() As String
 Get
 Return _title
 End Get
 Set(ByVal value As String)
 _title = value
 End Set
 End Property


 Private _link As String
 ''' <summary>
 ''' The URL for the Yahoo! Weather page of the forecast for this location. For example http://us.rd.yahoo.com/dailynews/rss/weather/ Sunnyvale__CA/ *http://xml.weather.yahoo.com/ forecast/94089_f.html
 ''' </summary>
 <XmlElement()> _
 Public Property link() As String
 Get
 Return _link
 End Get
 Set(ByVal value As String)
 _link = value
 End Set
 End Property

 Private _language As String
 ''' <summary>
 ''' The language of the weather forecast, for example, en-us for US English. 
 ''' </summary>
 <XmlElement()> _
 Public Property language() As String
 Get
 Return _language
 End Get
 Set(ByVal value As String)
 _language = value
 End Set
 End Property

 Private _description As String
 ''' <summary>
 ''' The overall description of the feed including the location, for example "Yahoo! Weather for Sunnyvale, CA" 
 ''' </summary>
 <XmlElement()> _
 Public Property description() As String
 Get
 Return _description
 End Get
 Set(ByVal value As String)
 _description = value
 End Set
 End Property

 Private _lastBuildDate As String
 ''' <summary>
 ''' The last time the feed was updated. The format is in the date format defined by RFC822 Section 5, for example Mon, 256 Sep 17:25:18 -0700.
 ''' </summary>
 <XmlElement()> _
 Public Property lastBuildDate() As String
 Get
 Return _lastBuildDate
 End Get
 Set(ByVal value As String)
 _lastBuildDate = value
 End Set
 End Property

 Private _ttl As String
 ''' <summary>
 ''' Time to Live; how long in minutes this feed should be cached. 
 ''' </summary>
 <XmlElement()> _
 Public Property ttl() As String
 Get
 Return _ttl
 End Get
 Set(ByVal value As String)
 _ttl = value
 End Set
 End Property

 Private _location As locationClass
 ''' <summary>
 ''' The location of this forecast.
 ''' </summary>
 <XmlElement()> _
 Public Property location() As locationClass
 Get
 Return _location
 End Get
 Set(ByVal value As locationClass)
 _location = value
 End Set
 End Property

 Private _units As unitsClass
 ''' <summary>
 ''' Units for various aspects of the forecast.
 ''' </summary>
 <XmlElement()> _
 Public Property units() As unitsClass
 Get
 Return _units
 End Get
 Set(ByVal value As unitsClass)
 _units = value
 End Set
 End Property

 Private _wind As windClass
 ''' <summary>
 ''' Forecast information about wind.
 ''' </summary>
 <XmlElement()> _
 Public Property wind() As windClass
 Get
 Return _wind
 End Get
 Set(ByVal value As windClass)
 _wind = value
 End Set
 End Property

 Private _atmosphere As atmosphereClass
 ''' <summary>
 ''' Forecast information about current atmospheric pressure, humidity, and visibility.
 ''' </summary>
 <XmlElement()> _
 Public Property atmosphere() As atmosphereClass
 Get
 Return _atmosphere
 End Get
 Set(ByVal value As atmosphereClass)
 _atmosphere = value
 End Set
 End Property

 Private _astronomy As astronomyClass
 ''' <summary>
 ''' Forecast information about current astronomical conditions.
 ''' </summary>
 <XmlElement()> _
 Public Property astronomy() As astronomyClass
 Get
 Return _astronomy
 End Get
 Set(ByVal value As astronomyClass)
 _astronomy = value
 End Set
 End Property
 Private _image As imageClass
 ''' <summary>
 ''' The image used to identify this feed
 ''' </summary>
 <XmlElement()> _
 Public Property image() As imageClass
 Get
 Return _image
 End Get
 Set(ByVal value As imageClass)
 _image = value
 End Set
 End Property
 Private _item As itemClass
 ''' <summary>
 ''' The local weather conditions and forecast for a specific location.
 ''' </summary>
 <XmlElement()> _
 Public Property item() As itemClass
 Get
 Return _item
 End Get
 Set(ByVal value As itemClass)
 _item = value
 End Set
 End Property
 End Class
 End Class
End Class

</td>
</tr></tbody></table>
在chanel中声明了他包含哪些子节点，同样我们也需要为这些子节点申明对象。
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
Imports Microsoft.VisualBasic
Imports System.Xml.Serialization
Partial Class YahooWeatherForecast
 Partial Class rssClass
 Partial Class channelClass
 Public Class atmosphereClass
 Private _humidity As Integer
 ''' <summary>
 ''' humidity, in percent 
 ''' </summary>
 <XmlAttribute()> _
 Public Property humidity() As Integer
 Get
 Return _humidity
 End Get
 Set(ByVal value As Integer)
 _humidity = value
 End Set
 End Property
 Private _visibility As Double
 ''' <summary>
 ''' in the units specified by the distance attribute of the units element (mi or km). Note that the visibility is specified as the actual value * 100. For example, a visibility of 16.5 miles will be specified as 1650. A visibility of 14 kilometers will appear as 1400. 
 ''' </summary>
 <XmlAttribute()> _
 Public Property visibility() As Double
 Get
 Return _visibility
 End Get
 Set(ByVal value As Double)
 _visibility = value
 End Set
 End Property

 Private _pressure As Double
 ''' <summary>
 ''' barometric pressure, in the units specified by the pressure attribute of the units element (in or mb).
 ''' </summary>
 <XmlAttribute()> _
 Public Property pressure() As Double
 Get
 Return _pressure
 End Get
 Set(ByVal value As Double)
 _pressure = value
 End Set
 End Property


 Private _rising As Integer
 ''' <summary>
 ''' state of the barometric pressure, steady = 0, rising = 1, falling = 2
 ''' </summary>
 <XmlAttribute()> _
 Public Property rising() As Integer
 Get
 Return _rising
 End Get
 Set(ByVal value As Integer)
 _rising = value
 End Set
 End Property
 End Class
 End Class
 End Class
End Class
</td>
</tr></tbody></table>
在申明完对象之后，我们就可以将xml文件转换为相应的对象。
代码如下：
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
 Dim doc As New System.Xml.XmlDocument()
 Dim str As String = "http://xml.weather.yahoo.com/forecastrss?p=" & p & "&u=" & U
 Dim c As rssClass
 'Load data 
 doc.Load(str)
 str = doc.OuterXml


 'XmlSerializer could not Serialize XML with this Elements so i just replace them with Null String!
 str = str.Replace("yweather:", "")
 str = str.Replace("geo:", "")
 'Dim str1 As String = """ : "

 Dim str1 = "isPermaLink=""false"""
 str = str.Replace(str1, "")
 str1 = " version=""2.0"" xmlns:yweather=""http://xml.weather.yahoo.com/ns/rss/1.0"" xmlns:geo=""http://www.w3.org/2003/01/geo/wgs84_pos#"""
 str = str.Replace(str1, "")
 Dim memoryStream As New IO.MemoryStream()
 Dim d As New IO.StringReader(str)

 Dim xs As New XmlSerializer(GetType(rssClass))

 c = CType(xs.Deserialize(d), rssClass)

 rss = c

</td>
</tr></tbody></table>
最后用户可以根据自己的需要将对象中的属性取出，使用于相关的应用中。类似如下代码
<table class="MsoTableGrid" style="border-collapse: collapse;" border="1" cellspacing="0" cellpadding="0"><tbody><tr style="">
<td style="padding-right: 5.4pt; padding-left: 5.4pt; padding-bottom: 0cm; width: 426.1pt; padding-top: 0cm; background-color: transparent; border: black 1pt solid;" width="568" valign="top">
 Dim t As New YahooWeatherLib.YahooWeatherForecast("CHXX0044", "f")
 Label1.Text = t.rss.channel.item.forecast.high
 Label2.Text = t.rss.channel.item.forecast.low
 Label5.Text = t.rss.channel.item.title
</td>
</tr></tbody></table>

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