设计方针(2)

    

　　通过因特网产生许多服务请求可能影响客户应用程序的性能。当设计你的XML Web服务时，通过创建把有关信息集中在一起的方法可以有效利用服务请求。例如，假定你有一个XML Web服务，用来检索一本书的信息。我们可以创建一个在一条服务请求中返回所有的信息的方法，来代替单独的检索书名、作者和出版社的方法。一次传送大块的信息比多次传送小块的信息更有效率。

　　下面的代码示例解释如何把有关信息组织到单个XML Web服务方法中。

[C#] ＜%@ WebService Language=\"C#\" Class=\"DataService\" %＞ using System; using System.Data; using System.Data.SqlClient; using System.Web.Services; public class DataService { [WebMethod] public DataSet GetTitleAuthors() { SqlConnection myConnection = new SqlConnection(\"Persist Security Info=False;Integrated Security=SSPI;server=localhost;database=pubs\"); SqlDataAdapter myCommand1 = new SqlDataAdapter (\"select * from Authors\", myConnection); SqlDataAdapter myCommand2 = new SqlDataAdapter(\"select * from Titles\", myConnection); DataSet ds = new DataSet(); myCommand1.Fill(ds, \"Authors\"); myCommand2.Fill(ds, \"Titles\"); return ds; } } [Visual Basic] ＜%@ WebService Language=\"VB\" Class=\"DataService\" %＞ Imports System Imports System.Data Imports System.Data.SqlClient Imports System.Web.Services Public Class DataService ＜WebMethod＞ _ Public Function GetTitleAuthors() As DataSet Dim myConnection As New SqlConnection(\"Persist Security Info=False;Integrated Security=SSPI;server=localhost;database=pubs\") Dim myCommand1 As New SqlDataAdapter(\"select * from Authors\", myConnection) Dim myCommand2 As New SqlDataAdapter(\"select * from Titles\", myConnection) Dim ds As New DataSet() myCommand1.Fill(ds, \"Authors\") myCommand2.Fill(ds, \"Titles\") Return ds End Function End Class

　　当设计你的XML Web服务时，请确保使用标准的面向对象编程操作。使用封装来隐藏实现细节。对于更复杂的XML Web服务，你可以使用继承和多态性来再次使用代码并简化你的设计。

　　下面的代码示例显示如何使用继承来创建一个执行数学计算的XML Web服务。

[C#] ＜%@ WebService Language=\"C#\" Class=\"Add\" %＞ using System; using System.Web.Services; abstract public class MathService : WebService { 　[WebMethod] 　abstract public float CalculateTotal(float a, float b); } public class Add : MathService { 　[WebMethod] 　override public float CalculateTotal(float a, float b) 　{ 　　return a + b; 　} } public class Subtract : MathService { 　[WebMethod] 　override public float CalculateTotal(float a, float b) 　{ 　　return a - b; 　} } public class Multiply : MathService { 　[WebMethod] 　override public float CalculateTotal(float a, float b) 　{ 　　return a * b; 　} } public class Divide : MathService { 　[WebMethod] 　override public float CalculateTotal(float a, float b) 　{ 　　if (b==0) 　　　return -1; 　　else 　　　return a / b; 　} } [Visual Basic] ＜%@ WebService Language=\"VB\" Class=\"Add\" %＞ Imports System Imports System.Web.Services MustInherit Public Class MathService : Inherits WebService ＜WebMethod＞ _ Public MustOverride Function CalculateTotal(a As Single, _ b As Single) As Single End Class Public Class Add : Inherits MathService ＜WebMethod＞ Public Overrides Function CalculateTotal(a As Single, b As Single) As Single Return a + b End Function End Class Public Class Subtract : Inherits MathService ＜WebMethod＞ Public Overrides Function CalculateTotal(a As Single, b As Single) As Single Return a - b End Function End Class Public Class Multiply : Inherits MathService ＜WebMethod＞ Public Overrides Function CalculateTotal(a As Single, b As Single) As Single Return a * b End Function End Class Public Class Divide : Inherits MathService ＜WebMethod＞ Public Overrides Function CalculateTotal(a As Single, b As Single) As Single 　If b = 0 Then 　　Return - 1 　Else 　　Return a / b 　End If End Function End Class