class procedure TMXMLPersistent.LoadObjFromXML(aNode: IXMLNode; aObj: TPersistent); Var i : Integer; pList : TMPropList; pInfo : PPropInfo; tmpObj: TObject; begin If ( aObj Is TMDataSetProxy ) Then ( aObj As TMDataSetProxy ).LoadFromXML( aNode ) Else Begin pList := TMPropList.Create( aObj ); Try For i := 0 To pList.PropCount - 1 Do Begin pInfo := pList.Props[i]; If ( pInfo^.PropType^.Kind = tkClass ) Then Begin tmpObj := TObject( Integer( GetPropValue( aObj, pInfo^.Name ) ) ); If ( Assigned( tmpObj ) AND ( tmpObj Is TPersistent ) ) Then LoadObjFromXML( aNode.ChildNodes[WideString(pInfo^.Name)], tmpObj As TPersistent ); End Else If ( pInfo^.PropType^.Kind In DefaultFilter ) Then SetPropValue( aObj, pInfo^.Name, String( aNode.ChildNodes[WideString( pInfo^.Name )].Text ) ); End; Finally pList.Free; End; End; end;
class procedure TMXMLPersistent.SaveObjToXML(aNode: IXMLNode; aObj: TPersistent); Var i : Integer; pList : TMPropList; pInfo : PPropInfo; tmpObj: TObject; begin If ( aObj Is TMDataSetProxy ) Then ( aObj As TMDataSetProxy ).SaveToXML( aNode ) Else Begin pList := TMPropList.Create( aObj ); Try For i := 0 To pList.PropCount - 1 Do Begin pInfo := pList.Props[i]; If ( pInfo^.PropType^.Kind = tkClass ) Then Begin tmpObj := TObject( Integer( GetPropValue( aObj, pInfo^.Name ) ) ); If ( Assigned( tmpObj ) AND ( tmpObj Is TPersistent ) ) Then SaveObjToXML( aNode.AddChild( WideString( pInfo^.Name ) ), tmpObj As TPersistent ); End Else If ( pInfo^.PropType^.Kind In DefaultFilter ) Then aNode.AddChild( WideString( pInfo^.Name ) ).Text := GetPropValue( aObj, pInfo^.Name ); End; Finally pList.Free; End; End; end;
procedure TMDataSetProxy.LoadFromXML(aNode: IXMLNode); Var i, j : Integer; pInfo : PPropInfo; pRow : IXMLNode; begin For j := 0 To aNode.ChildNodes.Count - 1 Do Begin FDataSet.Append; pRow := aNode.ChildNodes[j]; For i := 0 To FPropList.PropCount - 1 Do Begin pInfo := FPropList.Props[i]; If ( pInfo^.PropType^.Kind In DefaultFilter ) Then SetVariant( i, String( pRow.ChildNodes[WideString( pInfo^.Name )].Text ) ); End; EndEdit; End; FDataSet.First; end;
procedure TMDataSetProxy.SaveToXML(aNode: IXMLNode); Var i : Integer; pInfo : PPropInfo; pRow : IXMLNode; begin While ForEach Do Begin pRow := aNode.AddChild( 'Row' ); For i := 0 To FPropList.PropCount - 1 Do Begin pInfo := FPropList.Props[i]; If ( pInfo^.PropType^.Kind In DefaultFilter ) Then pRow.AddChild( WideString( pInfo^.Name ) ).Text := GetVariant( i ); End; End; end;
RTTI来实现Object的XML持久化,SOAP实现就是用RTTI来实现Object到SOAP数据(就是XML)的转换...TMXMLPersistent = class(TObject)
public
class Procedure LoadObjFromXML( aNode : IXMLNode; aObj : TPersistent );
class Procedure SaveObjToXML( aNode : IXMLNode; aObj : TPersistent );
end;
const
DefaultFilter : TTypeKinds = [tkInteger, tkChar, tkEnumeration,
tkFloat, tkString, tkSet, tkWChar, tkLString, tkWString, tkInt64];
{ TMXMLPersistent }
class procedure TMXMLPersistent.LoadObjFromXML(aNode: IXMLNode;
aObj: TPersistent);
Var
i : Integer;
pList : TMPropList;
pInfo : PPropInfo;
tmpObj: TObject;
begin
If ( aObj Is TMDataSetProxy ) Then
( aObj As TMDataSetProxy ).LoadFromXML( aNode )
Else
Begin
pList := TMPropList.Create( aObj );
Try
For i := 0 To pList.PropCount - 1 Do
Begin
pInfo := pList.Props[i];
If ( pInfo^.PropType^.Kind = tkClass ) Then
Begin
tmpObj := TObject( Integer( GetPropValue( aObj, pInfo^.Name ) ) );
If ( Assigned( tmpObj ) AND ( tmpObj Is TPersistent ) ) Then
LoadObjFromXML( aNode.ChildNodes[WideString(pInfo^.Name)],
tmpObj As TPersistent );
End
Else If ( pInfo^.PropType^.Kind In DefaultFilter ) Then
SetPropValue( aObj, pInfo^.Name,
String( aNode.ChildNodes[WideString( pInfo^.Name )].Text ) );
End;
Finally
pList.Free;
End;
End;
end;
class procedure TMXMLPersistent.SaveObjToXML(aNode: IXMLNode;
aObj: TPersistent);
Var
i : Integer;
pList : TMPropList;
pInfo : PPropInfo;
tmpObj: TObject;
begin
If ( aObj Is TMDataSetProxy ) Then
( aObj As TMDataSetProxy ).SaveToXML( aNode )
Else
Begin
pList := TMPropList.Create( aObj );
Try
For i := 0 To pList.PropCount - 1 Do
Begin
pInfo := pList.Props[i];
If ( pInfo^.PropType^.Kind = tkClass ) Then
Begin
tmpObj := TObject( Integer( GetPropValue( aObj, pInfo^.Name ) ) );
If ( Assigned( tmpObj ) AND ( tmpObj Is TPersistent ) ) Then
SaveObjToXML( aNode.AddChild( WideString( pInfo^.Name ) ),
tmpObj As TPersistent );
End
Else If ( pInfo^.PropType^.Kind In DefaultFilter ) Then
aNode.AddChild( WideString( pInfo^.Name ) ).Text :=
GetPropValue( aObj, pInfo^.Name );
End;
Finally
pList.Free;
End;
End;
end;
这个实现应该说是很简单的。主要是三个部分(Load和Save的结构是相似的):
一是对TMDataSetProxy作特别处理,委托给这个类自己去处理它的实现,因为它与一般的类不同,需要通过ForEach遍历全部记录,这其实就是同时实现数据集的XML持久化。
二是对Class作递归处理,当然只支持从TPersistent派生的class。
三是一般的Field简单地转成String保存,其中借鉴了lexlib的Filter,只处理那些能简单地转成String的数据类型,过滤掉那些可能造成转换出错的类型。
上面的代码中用到的TMPropList见《用DELPHI的RTTI实现数据集的简单对象化》中的实现。
下面是用TMDataSetProxy实现的数据集的XML持久化。免去了需要通过TClientDataSet进行的麻烦,并且采用的是用Node记录字段的方式,.net也是采用这样的方式,与TClientDataSet所用的用Attribute记录字段的方式不同。虽然这样生成的 XML文件将会略大一些,但是好处也是显而易见的,特别是我是准备用在Web应用中的,用Node方式记录的XML,在用XSLT时会方便很多。
procedure TMDataSetProxy.LoadFromXML(aNode: IXMLNode);
Var
i, j : Integer;
pInfo : PPropInfo;
pRow : IXMLNode;
begin
For j := 0 To aNode.ChildNodes.Count - 1 Do
Begin
FDataSet.Append;
pRow := aNode.ChildNodes[j];
For i := 0 To FPropList.PropCount - 1 Do
Begin
pInfo := FPropList.Props[i];
If ( pInfo^.PropType^.Kind In DefaultFilter ) Then
SetVariant( i,
String( pRow.ChildNodes[WideString( pInfo^.Name )].Text ) );
End;
EndEdit;
End;
FDataSet.First;
end;
procedure TMDataSetProxy.SaveToXML(aNode: IXMLNode);
Var
i : Integer;
pInfo : PPropInfo;
pRow : IXMLNode;
begin
While ForEach Do
Begin
pRow := aNode.AddChild( 'Row' );
For i := 0 To FPropList.PropCount - 1 Do
Begin
pInfo := FPropList.Props[i];
If ( pInfo^.PropType^.Kind In DefaultFilter ) Then
pRow.AddChild( WideString( pInfo^.Name ) ).Text
:= GetVariant( i );
End;
End;
end;
下面是一个简单的DEMO,其中包括了对数据集的XML持久化。注意Load的时候Employee成员连接的是ADODataSet2,它连接到一个包含了这几个字段的表,各字段类型与Employee表相同,但内容为空,并且去掉了EmployeeID的Identity。Load完成后,Employee表中这几个字段的内容将被复制到此表中。
TDemoCompany = class( TPersistent )
private
FEmployee : TDSPEmployee;
FCompany : String;
FCode : Integer;
published
property Employee : TDSPEmployee Read FEmployee Write FEmployee;
property Company : String Read FCompany Write FCompany;
Property Code : Integer Read FCode Write FCode;
End;
procedure TForm1.SaveClick(Sender: TObject);
Var
demo : TDemoCompany;
begin
demo := TDemoCompany.Create;
demo.Employee := TDSPEmployee.Create( ADODataSet1 );
demo.Company := 'Demo company';
demo.Code := 987654;
Try
XMLDocument1.Active := true;
TMXMLPersistent.SaveObjToXML( XMLDocument1.AddChild( 'Demo' ), demo );
XMLDocument1.SaveToFile( 'temp.xml' );
XMLDocument1.Active := false;
Finally
demo.Employee.Free;
demo.Employee := Nil;
demo.Free;
End;
end;
procedure TForm1.LoadClick(Sender: TObject);
Var
demo : TDemoCompany;
begin
demo := TDemoCompany.Create;
demo.Employee := TDSPEmployee.Create( ADODataSet2 );
Try
XMLDocument1.Active := true;
XMLDocument1.LoadFromFile( 'temp.xml' );
TMXMLPersistent.LoadObjFromXML( XMLDocument1.ChildNodes.Last, demo );
XMLDocument1.Active := false;
Edit1.Text := demo.Company;
Edit2.Text := IntToStr( demo.Code );
While ( demo.Employee.ForEach ) Do
With ListView1.Items.Add Do
Begin
Caption := IntToStr( demo.Employee.EmployeeID );
SubItems.Add( demo.Employee.FirstName );
SubItems.Add( demo.Employee.LastName );
SubItems.Add( FormatDateTime( 'yyyy-mm-dd', demo.Employee.BirthDate ) );
End;
Finally
demo.Employee.Free;
demo.Employee := Nil;
demo.Free;
End;
end;
不过相对的,我还是宁愿使用 xml 的 Data Bind 方法创建一个实例来用。
毕竟,一个项目中,能有多少个“配置”文件呢?
用最显而易见的方法比较合适我。同时,5也很佩服 猛禽 的钻研精神。
对这些数据对象进行相同的操作,回使得代码简单很多。