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Serialization

Submitted To:Submitted By:

Mrs. Monika Sharma Shankul Bahiya

09IT044

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Serialization/Deserialization

Object in memory

Object in memory

binary or character stream

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SerializationWhat is Serialization

Serialization is the process of converting an

object, or a connected graph of objects, stored

within computer memory, into a linear sequenceof bytes.

Use the sequence of bytes in several ways: Send it to another process

Send it to the clipboard, to be browsed or used byanother application

Send it to another machine

Send it to a file on disk

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SerializationObject Graph

What is an object graph? An object graph is a set of objects with some set of

references to each other

The most obvious problem is how to represent the links

between the objects in the Serialized stream

CatCat Mouse

Duck

Dog

2

1

3

4

9

7

Horse

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SerializaitonFileStream Example in VB

Dim fs As FileStream = New FileStream("obj.dat", FileMode.Create)

Dim bf As New BinaryFormatter()

' Serialize the class to the file stream, and flush the stream.

bf.Serialize(fs, New SerClass())

fs.Close()

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Serialization Formatter in VB

Binary Formatter :

The Binary Formatter object, defined in

System.Runtime.Serialization.Formatters. Binary namespace,

provides an efficient way to persist an object in a compact binary

format. In practice, the actual bits in memory are persisted, so theserialization and deserialization processes are very fast.

Soap Formatter :

The Soap Formatter object, defined in

System.Runtime.Serialization.Formatters. SOAP namespace,persists data in human-readable XML format, following the Simple

Object Access Protocol (SOAP) specifications. The serialization and

deserialization processes are somewhat slower than with the

BinaryFormatter object. On the other hand, data can be sent easily to

another application through HTTP and displayed in a human-

readable format.

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Binary Serialization

The key methods that all formatter objects support are Serialize and

Deserialize, whose purpose is rather evident. The Serialize method

takes a Stream object as its first argument and the object to be

serialized as its second argument:

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Cont.

Reading back the file data and deserializing it into an object requires

the Deserialize function, which takes the input Stream as its only

argument and returns an Object value, which must be cast to a

properly typed variable:

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Soap Serialization

You can change the serialization format to SOAP by simply

using another formatter object, the SoapFormatter. This

namespace isn't available in the default Visual Basic console

project, so you have to click Add Reference on the Projectmenu in Visual Studio to add the

System.Runtime.Serialization.Formatters.Soap.dll library to

the list of libraries that appears in the Object Browser. Note

that the SoapFormatter's constructor is passed aStreamingContext object that specifies where the

serialization data is stored:

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To make a user-defined class Serializable we have to use

attribute for a class as:

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Serialization in VC ++ ..

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Disk Files & Archieves

How do you know whether Serialize() should read or write

data? How is Serialize() connected to a disk file? With the

MFC library, objects of class CFile represent disk files. ACFile object encapsulates the binary file handle that you get

through the Win32 function CreateFile(). This is not the

buffered FILE pointer that you'd get with a call to the C

runtime fopen() function; rather, it's a handle to a binary file.The application framework uses this file handle for Win32

ReadFile(), WriteFile(), and SetFilePointer() calls.

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cont..

If your application does no direct disk I/O but instead relies on the

serialization process, you can avoid direct use of CFile objects.

Between the Serialize() function and the CFile object is an archive

object of class CArchive, as shown in Figure 1.

The CArchive object buffers data for the CFile object, and it

maintains an internal flag that indicates whether the archive is

storing (writing to disk) or loading (reading from disk). Only one

active archive is associated with a file at any one time. The

application framework takes care of constructing the CFile andCArchive objects, opening the disk file for the CFile object and

associating the archive object with the file. All you have to do (in

your Serialize() function) is load data from or store data in the

archive object. The application framework calls the document's

Serialize() function during the File Open and File Save processes.

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A serializable class must be derived directly or indirectly

from CObject. In addition (with some exceptions), the class

declaration must contain the DECLARE_SERIAL macro call,

and the class implementation file must contain theIMPLEMENT_SERIAL macro call. See the Microsoft

Foundation Class Reference for a description of these

macros. This module's CStudent class example is modified

from the class in Module 10 to include these macros.

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Writing a Serialize Function

Now, your job is to write a Serialize() member function for

CStudent. Because Serialize() is a virtual member functionof class CObject, you must be sure that the return value and

parameter types match the CObject declaration. The

Serialize() function for the CStudent class is below.

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Most serialization functions call the Serialize() functions of their base

classes. If CStudent were derived from CPerson, for example, the first

line of the Serialize() function would be: CPerson::Serialize(ar);

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The Serialize() function for CObject (and for CDocument,

which doesn't override it) doesn't do anything useful, so

there's no need to call it. Notice that ar is a CArchive

reference parameter that identifies the application's archiveobject. The CArchive::IsStoring member function tells us

whether the archive is currently being used for storing or

loading. The CArchive class has overloaded insertion

operators () for many ofthe C++ built-in types, as shown in the following table.

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Type Description

BYTE 8 bits, unsigned

WORD 16 bits, unsigned

LONG 32 bits, signed

DWORD 32 bits, unsigned

float 32 bits

double 64 bits, IEEE standard

int 32 bits, signed

short 16 bits, signed

char 8 bits, unsigned

unsigned 32 bits, unsigned

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The insertion operators are overloaded for values; the

extraction operators are overloaded for references.

Sometimes you must use a cast to satisfy the compiler.

Suppose you have a data member m_nType that is anenumerated type. Here's the code you would use:

ar > (int&) m_nType;

MFC classes that are not derived from CObject, such as

CString and CRect, have their own overloaded insertion

and extraction operators for CArchive.

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