Persistence concept

Common interfaces and implementations for file based persistence and general object serialization. More...

Namespaces
namespace	iser
	Contains general persistence mechanism with basic archives implementations.

Classes
class	ifile::CAutoPersistenceComp
	The component for automatic object persistence. More...
class	ifile::CCompactXmlFileReadArchive
	Qt-based implementation of archive reading from XML file. More...
class	ifile::CCompactXmlFileWriteArchive
	Qt-based implementation of archive for writing in compact XML format. More...
class	ifile::CComposedFileMetaInfoProviderComp
class	ifile::CComposedFilePersistenceComp
	Loader component, which delegates the persistence functionality to its slave loaders. More...
class	ifile::CCompressedXmlFileReadArchive
	Qt-based implementation of archive reading from XML file. More...
class	ifile::CCompressedXmlFileWriteArchive
	Qt-based implementation of archive for writing in compact XML format. More...
class	ifile::CFileArchiveInfo
	Basic implementation of interface ifile::IFileArchiveInfo. More...
class	ifile::CFileReadArchive
	Simple implementation of archive reading from own ACF format binary file. More...
class	ifile::CFileSerializerCompBase
	Base implementation of file serializer. More...
class	ifile::CFileTypeInfoComp
	Simple implementation of ifile::IFileTypeInfo using user defined extension list and descriptions. More...
class	ifile::CFileWriteArchive
	Simple implementation of archive writing to own ACF format binary file. More...
class	ifile::CSimpleXmlFileReadArchive
	Simple implementation of archive reading from XML file. More...
class	ifile::CSimpleXmlFileWriteArchive
	Simple implementation of archive for writing in XML format. More...
class	ifile::IDeviceBasedPersistence
	Interface providing reading and writing data objects via I/O-devices. More...
class	ifile::IFileArchiveInfo
	Simple informative interface allowing to get access to current processed file by file archives. More...
class	ifile::IFilePersistence
	Interface providing loading and saving of data objects. More...
class	ifile::IFilePersistenceInfo
	Provide some information about file loader state. More...
class	ifile::IFileTypeInfo
	Provide loading and saving of objects. More...
class	ifile::TDeviceBasedSerializerComp< ReadArchive, WriteArchive >
	Template implementation of file serializer using loading and storing archive implementation. More...
class	ifile::TFileSerializerComp< ReadArchive, WriteArchive >
	Template implementation of file serializer using loading and storing archive implementation. More...
class	ifile::TXmlFileSerializerComp< ReadArchive, WriteArchive >
	Template implementation of file serializer using loading and storing archive implementation. More...
class	iqt::CClipboardSerializerComp
	A clipboard serializer component. More...
class	iqt::CNetworkWriteArchive
	A write archive working over network connection. More...
class	iqt::CSettingsArchiveBase
	Basic implementation for an archive used Qt settings implementation as persistence medium. More...
class	iqt::CSettingsReadArchive
	The read archive used global system settings mechansim (by example Windows registry or INI file) as medium. More...
class	iqt::CSettingsSerializerComp
	Store and load parameter as global settings. More...
class	iqt::CSettingsWriteArchive
	Write archive implementation for serialization based on QSettings. More...
class	iser::CArchiveHeaderInfo
	Represents functions related to ACF header. More...
class	iser::CArchiveTag
	Process tag used to group data in archive stream. More...
class	iser::CBitMemoryReadArchive
	This class provides bitwise access to the byte data. More...
class	iser::CBitMemoryWriteArchive
	This is an archive implementation which provides bitwise write of data. More...
class	iser::CCompactXmlMemReadArchive
	Qt-based implementation of archive reading from XML file. More...
class	iser::CCompactXmlMemWriteArchive
	Qt-based implementation of archive for writing in XML format. More...
class	iser::CCompactXmlReadArchiveBase
	Qt-based implementation of archive reading from XML file. More...
class	iser::CMemoryReadArchive
	Implementation of archive using memory buffer to read the persistent objects. More...
class	iser::CMemoryWriteArchive
	Implementation of archive using memory buffer to store the persistent objects. More...
class	iser::CMinimalVersionInfo
	Implementation of interface iser::IVersionInfo using information about minimal needed version from interface iser::ISerializable. More...
class	iser::CWriteArchiveBase
	Basic implementation of an abstract archive for data writting. More...
class	iser::CXmlStringReadArchive
	Simple implementation for reading of a XML from a string. More...
class	iser::CXmlStringWriteArchive
	Simple implementation of archive for writing of XML given as a string. More...
class	iser::IArchive
	Represents an input/output persistence archive for object serialization. More...
class	iser::IObject
	Common interface for factorisable model objects. More...
class	iser::ISerializable
	Common class for all classes which objects can be archived or restored from archive. More...
class	iser::IVersionInfo
	Provides access to version information. More...

Detailed Description

Common interfaces and implementations for file based persistence and general object serialization.

Archive-based object serialization

Objects that provide serialization must implement the iser::ISerializable interface. The most important method of this interface is Serialize(). Serialize method becomes as input an so called archive (iser::IArchive). An archive provides an abstract low level read/write access to a data medium. By example an archive can represent a file, a memory block, a database or a network resource, but the concrete kind of the archive is completely hidden from data object's point of view. Thus, we create a complete separation between the data model and the medium on which it is to be made persistent. Following archive types are provided by ACF core libraries:

• Read from a memory block - iser::CMemoryReadArchive
• Write to a memory block - iser::CMemoryWriteArchive
• Read from a binary file - ifile::CFileReadArchive
• Write to a binary file - ifile::CFileWriteArchive
• Read from a fast parsed XML document given as a string - iser::CXmlStringReadArchive
• Write to a fast parsed XML-string - iser::CXmlStringWriteArchive
• Read from a fast parsed XML file - ifile::CSimpleXmlFileReadArchive
• Write to a fast parsed XML file - ifile::CSimpleXmlFileWriteArchive
• Read from a memory block bitwise - iser::CBitMemoryReadArchive
• Write to a memory block bitwise - iser::CBitMemoryWriteArchive
• Write to a TCP/IP socket - iqt::CNetworkWriteArchive
• Read from a compact XML document given as a string - iser::CCompactXmlMemReadArchive
• Write to a compact XML-string - iser::CCompactXmlMemWriteArchive
• Read from a compact XML file - ifile::CCompactXmlFileReadArchive
• Write to a compact XML file - ifile::CCompactXmlFileWriteArchive
• Read from a JSON file - ifile:CJsonFileReadArchive
• Write to a JSON file - ifile::CJsonFileWriteArchive
• Read from a JSON representation in memory - ifile:CJsonMemReadArchive
• Write to a JSON representation in memory - ifile::CJsonMemWriteArchive

We demonstrate the implementation of object serialization on example of CPerson class introduced in the Data model section. First of all we have to change the CPerson class to be inherited from iser::ISerializable. Because iser::ISerializable is already derived from istd::IChangeable, we have nothing else to change in this aspect. Also we rewrite:

class CPerson: virtual public iser::ISerializable
{
public:
       
       // reimplemented (iser::ISerializable)
       virtual bool Serialize(iser::IArchive& archive) override;
 
private:
       QString m_firstName;
       QString m_lastName;
};
 
// reimplemented (iser::ISerializable)
 
bool CPerson::Serialize(iser::IArchive& archive)
{
       bool retVal = true;
 
       // Use data model change notification only if the object will be reading from archive:
       istd::CChangeNotifier notifier(archive.IsStoring()? NULL: this);
 
       // Serialize object using tags:
 
       // Serialize first name of the person:
       static iser::CArchiveTag firstNameTag("FirstName", "First name of the person");
       retVal = retVal && archive.BeginTag(firstNameTag); // Begin tag
       retVal = retVal && archive.Process(m_firstName); // Process first name by archive   
       retVal = retVal && archive.EndTag(firstNameTag); // Close tag
 
       // Serialize last name of the person:
       static iser::CArchiveTag lastNameTag("LastName", "Last name of the person");
       retVal = retVal && archive.BeginTag(lastNameTag);
       retVal = retVal && archive.Process(m_lastName);
       retVal = retVal && archive.EndTag(lastNameTag);
 
       return retVal;
}

File-based persistence

Serialization is a low-level persistence mechanism, in which the structure of the archived data on the medium depends on Serialize method implementation inside of the data object. But often you will offer persistence functionality, that is not depending on concrete object implementation. A such situation is the supporting of known data formats (for example reading or writing of PNG images, OpenOffice documents and so on). For such persistence implementations ACF provides ifile::IFilePersistence interface.

See also

Data model