XML シリアル化の例
XML シリアル化は、単純な形式から複雑な形式に至るまで、さまざまな形で実行できます。たとえば、「XML シリアル化の概要」に示すように、パブリック フィールドとパブリック プロパティだけで構成されるクラスをシリアル化できます。次の例では、XML シリアル化を使用して特定の XML スキーマ (XSD) ドキュメントに準拠する XML ストリームを生成する方法など、各種の高度なシナリオに対応するコード例を示します。
データセットのシリアル化
次のコード例に示すように、パブリック クラスのインスタンスだけでなく、DataSet のインスタンスもシリアル化できます。
Private Sub SerializeDataSet(filename As String)
Dim ser As XmlSerializer = new XmlSerializer(GetType(DataSet))
' Creates a DataSet; adds a table, column, and ten rows.
Dim ds As DataSet = new DataSet("myDataSet")
Dim t As DataTable = new DataTable("table1")
Dim c As DataColumn = new DataColumn("thing")
t.Columns.Add(c)
ds.Tables.Add(t)
Dim r As DataRow
Dim i As Integer
for i = 0 to 10
r = t.NewRow()
r(0) = "Thing " & i
t.Rows.Add(r)
Next
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, ds)
writer.Close()
End Sub
private void SerializeDataSet(string filename){
XmlSerializer ser = new XmlSerializer(typeof(DataSet));
// Creates a DataSet; adds a table, column, and ten rows.
DataSet ds = new DataSet("myDataSet");
DataTable t = new DataTable("table1");
DataColumn c = new DataColumn("thing");
t.Columns.Add(c);
ds.Tables.Add(t);
DataRow r;
for(int i = 0; i<10;i++){
r = t.NewRow();
r[0] = "Thing " + i;
t.Rows.Add(r);
}
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, ds);
writer.Close();
}
XmlElement および XmlNode のシリアル化
次のコード例に示すように、XmlElement クラスまたは XmlNode クラスのインスタンスもシリアル化できます。
private Sub SerializeElement(filename As String)
Dim ser As XmlSerializer = new XmlSerializer(GetType(XmlElement))
Dim myElement As XmlElement = _
new XmlDocument().CreateElement("MyElement", "ns")
myElement.InnerText = "Hello World"
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, myElement)
writer.Close()
End Sub
Private Sub SerializeNode(filename As String)
Dim ser As XmlSerializer = _
new XmlSerializer(GetType(XmlNode))
Dim myNode As XmlNode = new XmlDocument(). _
CreateNode(XmlNodeType.Element, "MyNode", "ns")
myNode.InnerText = "Hello Node"
Dim writer As TextWriter = new StreamWriter(filename)
ser.Serialize(writer, myNode)
writer.Close()
End Sub
private void SerializeElement(string filename){
XmlSerializer ser = new XmlSerializer(typeof(XmlElement));
XmlElement myElement=
new XmlDocument().CreateElement("MyElement", "ns");
myElement.InnerText = "Hello World";
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, myElement);
writer.Close();
}
private void SerializeNode(string filename){
XmlSerializer ser = new XmlSerializer(typeof(XmlNode));
XmlNode myNode= new XmlDocument().
CreateNode(XmlNodeType.Element, "MyNode", "ns");
myNode.InnerText = "Hello Node";
TextWriter writer = new StreamWriter(filename);
ser.Serialize(writer, myNode);
writer.Close();
}
複雑なオブジェクトを返すフィールドを含むクラスのシリアル化
プロパティやフィールドが複雑なオブジェクト (配列やクラス インスタンスなど) を返す場合、XmlSerializer は、そのオブジェクトをメイン XML ドキュメント内で入れ子になっている要素に変換します。たとえば、次のコード例の最初のクラスは、2 番目のクラスのインスタンスを返します。
Public Class PurchaseOrder
Public MyAdress As Address
End Class
Public Class Address
Public FirstName As String
End Class
public class PurchaseOrder
{
public Address MyAddress;
}
public class Address
{
public string FirstName;
}
シリアル化された XML 出力は次のようになります。
<PurchaseOrder>
<Address>
<FirstName>George</FirstName>
</Address>
</PurchaseOrder>
オブジェクト配列のシリアル化
次のコード例に示すように、オブジェクトの配列を返すフィールドをシリアル化することもできます。
Public Class PurchaseOrder
public ItemsOrders () As Item
End Class
Public Class Item
Public ItemID As String
Public ItemPrice As decimal
End Class
public class PurchaseOrder
{
public Item [] ItemsOrders
}
public class Item
{
public string ItemID
public decimal ItemPrice
}
シリアル化されたクラスのインスタンスは、2 つの品目が注文された場合、次のようになります。
<PurchaseOrder xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<Items>
<Item>
<ItemID>aaa111</ItemID>
<ItemPrice>34.22</ItemPrice>
<Item>
<Item>
<ItemID>bbb222</ItemID>
<ItemPrice>2.89</ItemPrice>
<Item>
</Items>
</PurchaseOrder>
ICollection インターフェイスを実装するクラスのシリアル化
ICollection インターフェイスを実装して独自のコレクション クラスを作成し、XmlSerializer を使用して、これらのクラスのインスタンスをシリアル化できます。クラスが ICollection インターフェイスを実装する場合、そのクラスに含まれているコレクションだけがシリアル化されます。このクラスに追加されたパブリック プロパティやパブリック フィールドはシリアル化されません。シリアル化するには、クラスに Add メソッドと Item プロパティ (C# の場合はインデクサ) を含める必要があります。
Imports System
Imports System.IO
Imports System.Collections
Imports System.Xml.Serialization
Public Class Test
Shared Sub Main()
Dim t As Test= new Test()
t.SerializeCollection("coll.xml")
End Sub
Private Sub SerializeCollection(filename As String)
Dim Emps As Employees = new Employees()
' Note that only the collection is serialized -- not the
' CollectionName or any other public property of the class.
Emps.CollectionName = "Employees"
Dim John100 As Employee = new Employee("John", "100xxx")
Emps.Add(John100)
Dim x As XmlSerializer = new XmlSerializer(GetType(Employees))
Dim writer As TextWriter = new StreamWriter(filename)
x.Serialize(writer, Emps)
writer.Close()
End Sub
End Class
Public Class Employees
Implements ICollection
Public CollectionName As String
Private empArray As ArrayList = new ArrayList()
Public ReadOnly Default Overloads _
Property Item(index As Integer) As Employee
get
return CType (empArray(index), Employee)
End Get
End Property
Public Sub CopyTo(a As Array, index As Integer) _
Implements ICollection.CopyTo
empArray.CopyTo(a, index)
End Sub
Public ReadOnly Property Count () As integer Implements _
ICollection.Count
get
Count = empArray.Count
End Get
End Property
Public ReadOnly Property SyncRoot ()As Object _
Implements ICollection.SyncRoot
get
return me
End Get
End Property
Public ReadOnly Property IsSynchronized () As Boolean _
Implements ICollection.IsSynchronized
get
return false
End Get
End Property
Public Function GetEnumerator() As IEnumerator _
Implements IEnumerable.GetEnumerator
return empArray.GetEnumerator()
End Function
Public Function Add(newEmployee As Employee) As Integer
empArray.Add(newEmployee)
return empArray.Count
End Function
End Class
Public Class Employee
Public EmpName As String
Public EmpID As String
Public Sub New ()
End Sub
Public Sub New (newName As String , newID As String )
EmpName = newName
EmpID = newID
End Sub
End Class
using System;
using System.IO;
using System.Collections;
using System.Xml.Serialization;
public class Test{
static void Main(){
Test t = new Test();
t.SerializeCollection("coll.xml");
}
private void SerializeCollection(string filename){
Employees Emps = new Employees();
// Note that only the collection is serialized -- not the
// CollectionName or any other public property of the class.
Emps.CollectionName = "Employees";
Employee John100 = new Employee("John", "100xxx");
Emps.Add(John100);
XmlSerializer x = new XmlSerializer(typeof(Employees));
TextWriter writer = new StreamWriter(filename);
x.Serialize(writer, Emps);
}
}
public class Employees:ICollection{
public string CollectionName;
private ArrayList empArray = new ArrayList();
public Employee this[int index]{
get{return (Employee) empArray[index];}
}
public void CopyTo(Array a, int index){
empArray.CopyTo(a, index);
}
public int Count{
get{return empArray.Count;}
}
public object SyncRoot{
get{return this;}
}
public bool IsSynchronized{
get{return false;}
}
public IEnumerator GetEnumerator(){
return empArray.GetEnumerator();
}
public void Add(Employee newEmployee){
empArray.Add(newEmployee);
}
}
public class Employee{
public string EmpName;
public string EmpID;
public Employee(){}
public Employee(string empName, string empID){
EmpName = empName;
EmpID = empID;
}
}
注文書の例
次のコード例を切り取って、.cs または .vb というファイル名拡張子を付けて名前を変更したテキスト ファイルに貼り付けます。そのファイルを、C# コンパイラまたは Visual Basic コンパイラを使用してコンパイルします。その後、実行可能ファイルの名前を使用して、このコードを実行します。
この例では、単純なシナリオとして、Serialize メソッドを使用してオブジェクトのインスタンスを作成し、ファイル ストリームにシリアル化する方法を示しています。この XML ストリームをファイルに保存した後、Deserialize メソッドを使用して同じファイルを再び読み込み、元のオブジェクトのコピーを再構築します。
この例では、PurchaseOrder という名前のクラスをシリアル化し、さらに逆シリアル化します。また、ShipTo という名前のパブリック フィールドを Address に設定する必要があるため、Address という名前の 2 番目のクラスも含まれています。同様に、OrderedItem オブジェクトの配列を OrderedItems フィールドに設定する必要があるため、OrderedItem クラスも含まれています。最後に、Test という名前のクラスには、これらのクラスをシリアル化および逆シリアル化するコードが含まれています。
CreatePO メソッドは、PurchaseOrder、Address、OrderedItem の各クラス オブジェクトを作成し、それらのパブリック フィールドの値を設定します。このメソッドは、PurchaseOrder のシリアル化および逆シリアル化に使用される XmlSerializer クラスのインスタンスも生成します。このコードは、シリアル化されるクラスの型をコンストラクタに渡します。さらに、XML ストリームを XML ドキュメントに書き込むために使用する FileStream も作成します。
ReadPo メソッドは、もう少し単純です。このメソッドは、逆シリアル化する対象となるオブジェクトを作成し、その値を読み取るだけです。CreatePo メソッドの場合と同様に、まず、逆シリアル化の対象となるクラスの型をコンストラクタに渡して、XmlSerializer を生成する必要があります。また、XML ドキュメントを読み取るため、FileStream も必要です。オブジェクトを逆シリアル化するには、この FileStream を引数として Deserialize メソッドを呼び出します。逆シリアル化されたオブジェクトは、PurchaseOrder 型のオブジェクト変数にキャストする必要があります。その後で、逆シリアル化された PurchaseOrder の値を読み取ります。作成された PO.xml ファイルを読み取って、実際の XML 出力を確認することもできます。
Imports System
Imports System.Xml
Imports System.Xml.Serialization
Imports System.IO
Imports Microsoft.VisualBasic
' The XmlRootAttribute allows you to set an alternate name
' (PurchaseOrder) for the XML element and its namespace. By
' default, the XmlSerializer uses the class name. The attribute
' also allows you to set the XML namespace for the element. Lastly,
' the attribute sets the IsNullable property, which specifies whether
' the xsi:null attribute appears if the class instance is set to
' a null reference.
<XmlRootAttribute("PurchaseOrder", _
Namespace := "http://www.cpandl.com", IsNullable := False)> _
Public Class PurchaseOrder
Public ShipTo As Address
Public OrderDate As String
' The XmlArrayAttribute changes the XML element name
' from the default of "OrderedItems" to "Items".
<XmlArrayAttribute("Items")> _
Public OrderedItems() As OrderedItem
Public SubTotal As Decimal
Public ShipCost As Decimal
Public TotalCost As Decimal
End Class
Public Class Address
' The XmlAttribute instructs the XmlSerializer to serialize the
' Name field as an XML attribute instead of an XML element (the
' default behavior).
<XmlAttribute()> _
Public Name As String
Public Line1 As String
' Setting the IsNullable property to false instructs the
' XmlSerializer that the XML attribute will not appear if
' the City field is set to a null reference.
<XmlElementAttribute(IsNullable := False)> _
Public City As String
Public State As String
Public Zip As String
End Class
Public Class OrderedItem
Public ItemName As String
Public Description As String
Public UnitPrice As Decimal
Public Quantity As Integer
Public LineTotal As Decimal
' Calculate is a custom method that calculates the price per item
' and stores the value in a field.
Public Sub Calculate()
LineTotal = UnitPrice * Quantity
End Sub
End Class
Public Class Test
Public Shared Sub Main()
' Read and write purchase orders.
Dim t As New Test()
t.CreatePO("po.xml")
t.ReadPO("po.xml")
End Sub
Private Sub CreatePO(filename As String)
' Creates an instance of the XmlSerializer class;
' specifies the type of object to serialize.
Dim serializer As New XmlSerializer(GetType(PurchaseOrder))
Dim writer As New StreamWriter(filename)
Dim po As New PurchaseOrder()
' Creates an address to ship and bill to.
Dim billAddress As New Address()
billAddress.Name = "Teresa Atkinson"
billAddress.Line1 = "1 Main St."
billAddress.City = "AnyTown"
billAddress.State = "WA"
billAddress.Zip = "00000"
' Set ShipTo and BillTo to the same addressee.
po.ShipTo = billAddress
po.OrderDate = System.DateTime.Now.ToLongDateString()
' Creates an OrderedItem.
Dim i1 As New OrderedItem()
i1.ItemName = "Widget S"
i1.Description = "Small widget"
i1.UnitPrice = CDec(5.23)
i1.Quantity = 3
i1.Calculate()
' Inserts the item into the array.
Dim items(0) As OrderedItem
items(0) = i1
po.OrderedItems = items
' Calculates the total cost.
Dim subTotal As New Decimal()
Dim oi As OrderedItem
For Each oi In items
subTotal += oi.LineTotal
Next oi
po.SubTotal = subTotal
po.ShipCost = CDec(12.51)
po.TotalCost = po.SubTotal + po.ShipCost
' Serializes the purchase order, and close the TextWriter.
serializer.Serialize(writer, po)
writer.Close()
End Sub
Protected Sub ReadPO(filename As String)
' Creates an instance of the XmlSerializer class;
' specifies the type of object to be deserialized.
Dim serializer As New XmlSerializer(GetType(PurchaseOrder))
' If the XML document has been altered with unknown
' nodes or attributes, handles them with the
' UnknownNode and UnknownAttribute events.
AddHandler serializer.UnknownNode, AddressOf serializer_UnknownNode
AddHandler serializer.UnknownAttribute, AddressOf _
serializer_UnknownAttribute
' A FileStream is needed to read the XML document.
Dim fs As New FileStream(filename, FileMode.Open)
' Declare an object variable of the type to be deserialized.
Dim po As PurchaseOrder
' Uses the Deserialize method to restore the object's state
' with data from the XML document.
po = CType(serializer.Deserialize(fs), PurchaseOrder)
' Reads the order date.
Console.WriteLine(("OrderDate: " & po.OrderDate))
' Reads the shipping address.
Dim shipTo As Address = po.ShipTo
ReadAddress(shipTo, "Ship To:")
' Reads the list of ordered items.
Dim items As OrderedItem() = po.OrderedItems
Console.WriteLine("Items to be shipped:")
Dim oi As OrderedItem
For Each oi In items
Console.WriteLine((ControlChars.Tab & oi.ItemName & _
ControlChars.Tab & _
oi.Description & ControlChars.Tab & oi.UnitPrice & _
ControlChars.Tab & _
oi.Quantity & ControlChars.Tab & oi.LineTotal))
Next oi
' Reads the subtotal, shipping cost, and total cost.
Console.WriteLine((ControlChars.Cr & New String _
(ControlChars.Tab, 5) & _
" Subtotal" & ControlChars.Tab & po.SubTotal & ControlChars.Cr & _
New String(ControlChars.Tab, 5) & " Shipping" & ControlChars.Tab & _
po.ShipCost & ControlChars.Cr & New String(ControlChars.Tab, 5) & _
" Total" & New String(ControlChars.Tab, 2) & po.TotalCost))
End Sub
Protected Sub ReadAddress(a As Address, label As String)
' Reads the fields of the Address.
Console.WriteLine(label)
Console.Write((ControlChars.Tab & a.Name & ControlChars.Cr & _
ControlChars.Tab & a.Line1 & ControlChars.Cr & ControlChars.Tab & _
a.City & ControlChars.Tab & a.State & ControlChars.Cr & _
ControlChars.Tab & a.Zip & ControlChars.Cr))
End Sub
Protected Sub serializer_UnknownNode(sender As Object, e As _
XmlNodeEventArgs)
Console.WriteLine(("Unknown Node:" & e.Name & _
ControlChars.Tab & e.Text))
End Sub
Protected Sub serializer_UnknownAttribute(sender As Object, _
e As XmlAttributeEventArgs)
Dim attr As System.Xml.XmlAttribute = e.Attr
Console.WriteLine(("Unknown attribute " & attr.Name & "='" & _
attr.Value & "'"))
End Sub 'serializer_UnknownAttribute
End Class 'Test
using System;
using System.Xml;
using System.Xml.Serialization;
using System.IO;
// The XmlRootAttribute allows you to set an alternate name
// (PurchaseOrder) for the XML element and its namespace. By
// default, the XmlSerializer uses the class name. The attribute
// also allows you to set the XML namespace for the element. Lastly,
// the attribute sets the IsNullable property, which specifies whether
// the xsi:null attribute appears if the class instance is set to
// a null reference.
[XmlRootAttribute("PurchaseOrder", Namespace="http://www.cpandl.com",
IsNullable = false)]
public class PurchaseOrder
{
public Address ShipTo;
public string OrderDate;
// The XmlArrayAttribute changes the XML element name
// from the default of "OrderedItems" to "Items".
[XmlArrayAttribute("Items")]
public OrderedItem[] OrderedItems;
public decimal SubTotal;
public decimal ShipCost;
public decimal TotalCost;
}
public class Address
{
// The XmlAttribute instructs the XmlSerializer to serialize the
// Name field as an XML attribute instead of an XML element (the
// default behavior).
[XmlAttribute]
public string Name;
public string Line1;
// Setting the IsNullable property to false instructs the
// XmlSerializer that the XML attribute will not appear if
// the City field is set to a null reference.
[XmlElementAttribute(IsNullable = false)]
public string City;
public string State;
public string Zip;
}
public class OrderedItem
{
public string ItemName;
public string Description;
public decimal UnitPrice;
public int Quantity;
public decimal LineTotal;
// Calculate is a custom method that calculates the price per item
// and stores the value in a field.
public void Calculate()
{
LineTotal = UnitPrice * Quantity;
}
}
public class Test
{
public static void Main()
{
// Read and write purchase orders.
Test t = new Test();
t.CreatePO("po.xml");
t.ReadPO("po.xml");
}
private void CreatePO(string filename)
{
// Creates an instance of the XmlSerializer class;
// specifies the type of object to serialize.
XmlSerializer serializer =
new XmlSerializer(typeof(PurchaseOrder));
TextWriter writer = new StreamWriter(filename);
PurchaseOrder po=new PurchaseOrder();
// Creates an address to ship and bill to.
Address billAddress = new Address();
billAddress.Name = "Teresa Atkinson";
billAddress.Line1 = "1 Main St.";
billAddress.City = "AnyTown";
billAddress.State = "WA";
billAddress.Zip = "00000";
// Sets ShipTo and BillTo to the same addressee.
po.ShipTo = billAddress;
po.OrderDate = System.DateTime.Now.ToLongDateString();
// Creates an OrderedItem.
OrderedItem i1 = new OrderedItem();
i1.ItemName = "Widget S";
i1.Description = "Small widget";
i1.UnitPrice = (decimal) 5.23;
i1.Quantity = 3;
i1.Calculate();
// Inserts the item into the array.
OrderedItem [] items = {i1};
po.OrderedItems = items;
// Calculate the total cost.
decimal subTotal = new decimal();
foreach(OrderedItem oi in items)
{
subTotal += oi.LineTotal;
}
po.SubTotal = subTotal;
po.ShipCost = (decimal) 12.51;
po.TotalCost = po.SubTotal + po.ShipCost;
// Serializes the purchase order, and closes the TextWriter.
serializer.Serialize(writer, po);
writer.Close();
}
protected void ReadPO(string filename)
{
// Creates an instance of the XmlSerializer class;
// specifies the type of object to be deserialized.
XmlSerializer serializer = new XmlSerializer(typeof(PurchaseOrder));
// If the XML document has been altered with unknown
// nodes or attributes, handles them with the
// UnknownNode and UnknownAttribute events.
serializer.UnknownNode+= new
XmlNodeEventHandler(serializer_UnknownNode);
serializer.UnknownAttribute+= new
XmlAttributeEventHandler(serializer_UnknownAttribute);
// A FileStream is needed to read the XML document.
FileStream fs = new FileStream(filename, FileMode.Open);
// Declares an object variable of the type to be deserialized.
PurchaseOrder po;
// Uses the Deserialize method to restore the object's state
// with data from the XML document. */
po = (PurchaseOrder) serializer.Deserialize(fs);
// Reads the order date.
Console.WriteLine ("OrderDate: " + po.OrderDate);
// Reads the shipping address.
Address shipTo = po.ShipTo;
ReadAddress(shipTo, "Ship To:");
// Reads the list of ordered items.
OrderedItem [] items = po.OrderedItems;
Console.WriteLine("Items to be shipped:");
foreach(OrderedItem oi in items)
{
Console.WriteLine("\t"+
oi.ItemName + "\t" +
oi.Description + "\t" +
oi.UnitPrice + "\t" +
oi.Quantity + "\t" +
oi.LineTotal);
}
// Reads the subtotal, shipping cost, and total cost.
Console.WriteLine(
"\n\t\t\t\t\t Subtotal\t" + po.SubTotal +
"\n\t\t\t\t\t Shipping\t" + po.ShipCost +
"\n\t\t\t\t\t Total\t\t" + po.TotalCost
);
}
protected void ReadAddress(Address a, string label)
{
// Reads the fields of the Address.
Console.WriteLine(label);
Console.Write("\t"+
a.Name +"\n\t" +
a.Line1 +"\n\t" +
a.City +"\t" +
a.State +"\n\t" +
a.Zip +"\n");
}
protected void serializer_UnknownNode
(object sender, XmlNodeEventArgs e)
{
Console.WriteLine("Unknown Node:" + e.Name + "\t" + e.Text);
}
protected void serializer_UnknownAttribute
(object sender, XmlAttributeEventArgs e)
{
System.Xml.XmlAttribute attr = e.Attr;
Console.WriteLine("Unknown attribute " +
attr.Name + "='" + attr.Value + "'");
}
}
XML 出力は、次のようになります。
<?xml version="1.0" encoding="utf-8"?>
<PurchaseOrder xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.cpandl.com">
<ShipTo Name="Teresa Atkinson">
<Line1>1 Main St.</Line1>
<City>AnyTown</City>
<State>WA</State>
<Zip>00000</Zip>
</ShipTo>
<OrderDate>Wednesday, June 27, 2001</OrderDate>
<Items>
<OrderedItem>
<ItemName>Widget S</ItemName>
<Description>Small widget</Description>
<UnitPrice>5.23</UnitPrice>
<Quantity>3</Quantity>
<LineTotal>15.69</LineTotal>
</OrderedItem>
</Items>
<SubTotal>15.69</SubTotal>
<ShipCost>12.51</ShipCost>
<TotalCost>28.2</TotalCost>
</PurchaseOrder>
関連項目
タスク
方法 : オブジェクトをシリアル化する
方法 : オブジェクトを逆シリアル化する
参照
概念
XML シリアル化の概要
属性を使用した XML シリアル化の制御
XML シリアル化を制御する属性
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