Xml Serialization - Basic Usage

This post relates to XmlSerial.pas which provides XML serialization and de-serialization using the new RTTI in Delphi 2010.

This class has been built to serialize any public and published property or Field.
This was done to mimic the behavior found in the .NET Xml Serialization with the goal of having a set of objects that can serialize in .NET using Delphi Prism and Win32 using Delphi 2010. The complete goals of what I want to accomplish with XmlSerial.pas look at the source code, I detailed out what still needs to be done.

There are two ways to work with the Xml Serialization, one depends on a Pointer to the Type Information, the other uses Generics to get it form the type specified as a parameter.

// Method 1:
var
 o : TypeIWantToSerailze;
 s : TXmlTypeSerializer;
 x : TXmlDocument;
 v : TValue;
begin
  s := TXmlTypeSerializer.create(TypeInfo(o));
  x := TXmlDocument.Create(Self); // NEVER PASS NIL!!!
  s.Serialize(x,o);
  x.SaveToFile('FileName.txt');
  v := s.Deserialize(x);
  o := v.AsType<TypeIWantToSerailze>;
  x.free;
  s.free;
end;

// Method 2:
var
 o : TypeIWantToSerailze;
 s : TXmlSerializer<TypeIWantToSerailze>;
 x : TXmlDocument;
begin
  s := TXmlTypeSerializer<TypeIWantToSerailze>.create;
  x := TXmlDocument.Create(Self); // NEVER PASS NIL!!!
  s.Serialize(x,o);
  x.SaveToFile('FileName.txt');
  o := s.Deserialize(x);
  x.free;
  s.free;
end;

And here is the full code showing how to do this using the generic version.

unit uPerson;
interface

type
  TPerson = class(TObject)
  private
    FLastName: String;
    FBirthday: TDateTime;
    FMiddleName: String;
    FFirstName: String;
    function GetFullName: String;
   published
   public
     property FirstName : String read FFirstName write FFirstName;
     property LastName  : String read FLastName  write FLastName;
     property MiddleName : String read FMiddleName write FMiddleName;
     property FullName : String read GetFullName;
     property Birthday : TDateTime read FBirthday write FBirthday;
     procedure Save(FileName : String);
     class function Load(FileName : String) : TPerson;
   end;


implementation
uses
 XmlDoc,
 Classes,
 XmlSerial;

{ TPerson }

function TPerson.GetFullName: String;
begin
 result := FFirstName + ' ' + FMiddleName + ' ' + FLastName;
end;

class function TPerson.Load(FileName: String): TPerson;
var
  lSerialize : TXmlSerializer<TPerson>;
  lOwner : TComponent;
  lDoc   : TxmlDocument;
begin
  lOwner := TComponent.Create(nil);  // Required to make TXmlDocument work!
  try
    lDoc := TXmlDocument.Create(lOwner);  // will be freed with lOwner.Free
    lDoc.LoadFromFile(FileName);
    lSerialize := TXmlSerializer<TPerson>.Create;
    try
      result := lSerialize.Deserialize(lDoc);
    finally
      lSerialize.Free;
    end;
  finally
    lOwner.Free;
  end;
end;

procedure TPerson.Save(FileName: String);
var
  lSerialize : TXmlSerializer<TPerson>;
  lOwner : TComponent;
  lDoc   : TxmlDocument;
begin
  lOwner := TComponent.Create(nil);  // Required to make TXmlDocument work!
  try
    lDoc := TXmlDocument.Create(lOwner);  // will be freed with lOwner.Free
    lSerialize := TXmlSerializer<TPerson>.Create;
    try
      lSerialize.Serialize(lDoc,Self);
      lDoc.SaveToFile(FileName);
    finally
      lSerialize.Free;
    end;
  finally
    lOwner.Free;
  end;
end;

end.

The project that shows how to use this object.

program Project12;

{$APPTYPE CONSOLE}

uses
  SysUtils,
  Windows,
  XmlSerial,
  Forms,
  uPerson in 'uPerson.pas';

var
  P : TPerson;

begin
  Application.Initialize;
  P := TPerson.Create;
  try
   P.FirstName := 'John';
   P.MiddleName := 'C';
   P.LastName := 'Doe';
   P.Birthday := EncodeDate(1995,2,14);
   P.Save('C:\test.xml');
  finally
    P.Free;
  end;

  p := TPerson.Load('C:\test.xml');
  try
    writeln(P.FullName);
    Writeln(DateToStr(P.Birthday));
    Readln;
  finally
    p.Free;
  end;
end.

Output:

John C Doe
2/14/1995

Current output of the XML file, notice the Date, it's something I want to change, if you check the roadmap in the xmlserial.pas source.

<TPerson>
   <FirstName>John</FirstName>
   <LastName>Doe</LastName>
   <MiddleName>C</MiddleName>
   <Birthday>34744</Birthday>
</TPerson>

Hopefully this covers enough of how to use this to get you started.
I will show how to customize the behavior using attributes in a future post.

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