Peter Hinrichsen TechInsite Pty Ltd Rolling your own Object Persistence Framework (OPF) Please consider the following questions: What do you expect from an OPF? What do you expect from this tutorial?

Tutorial Topics n Part 1: What is an OPF? What can an OPF do for me? n Part 2: The core principles of the tiOPF. n Part 3: A worked example of using the tiOPF

What is an OPF? n What is an OPF? What do you expect from an OPF? n Demo of an OPF application. n Why build an OPF. RAD vs OPF. n Ambler, Jedi-Obiwan and my design requirements of an OPF. n Architecture of the tiOPF

What do you expect from an OPF? n How long have you used Delphi? n What do you build with Delphi? n How to you currently build your apps? n What is an OPF? What do you expect from an OPF? n 1. n 2.

What is an OPF? n What is an OPF? What do you expect from an OPF? n Demo of an OPF application. n Why build an OPF. RAD vs OPF. n Ambler, Jedi-Obiwan and my design requirements of an OPF. n Architecture of the tiOPF

Demonstration - the address book application

What is an OPF? n What is an OPF? What do you expect from an OPF? n Demo of an OPF application. n Why build an OPF. RAD vs OPF. n Ambler, Jedi-Obiwan and my design requirements of an OPF. n Architecture of the tiOPF

Definitions: RAD and OPF n RAD: TDataModule, TQuery, TDatabase, TClientDataSet and data aware controls. OPF: Custom persistence layer, custom business objects and custom edit controls 

Advantages of RAD & Data Aware Controls 4Good for prototypes. 4Good for simple, single tier apps. 4Good for seldom used forms, like one-off setup screens that may be used to populate a new database with background data. 4Plenty of third party controls available.  Can re-configure themselves as the database schema changes (sometimes) 

Disadvantages of RAD & Data Aware Controls 6Higher maintenance and debugging costs. 6Higher network traffic. 6Can not be used to edit custom file formats, registry entries or data that is not contained in a TDataSet. 6Harder to develop data aware controls than regular controls. 6Hard to use when the DB does not map directly into the GUI ie, a well normalised database.  Difficult to make extensive reuse of code 

When do I use RAD and data aware controls? 4Low end customers (small businesses with few user). 4Throw away prototypes. 4Data maintenance apps that my customers will not see. 4Systems where I have total control over the database design.  When the user wants the app to look and perform as if it were written in VB 

Advantages of an OPF 4Good for complex applications. 4Lower network traffic. 4When the database is storing non text data like multi- media, or perhaps scientific data which must be manipulated with complex algorithms. 4Decouple GUI from database - multiple databases  Lower total cost of ownership 

Disadvantages of an OPF 6More skilled development team. 6Higher up front development cost. 6Many reporting tools take input from a TDataSet. Some extra code would be needed to connect the persistence framework to the reporting tool.  Must re-build what comes out of the box with Delphi 

When do I use an OPF? 4High end (corporate) customers with many users where performance is important. 4Systems that have complex data models that I have little control over. 4Systems that require a TreeView, ListView look and feel.  Systems that must be database vendor independent 

What is an OPF? n What is an OPF? What do you expect from an OPF? n Demo of an OPF application. n Why build an OPF. RAD vs OPF. n Ambler, Jedi-Obiwan and my design requirements of an OPF. n Architecture of the tiOPF

Ambler, Obiwan & PWH’s requirements of an OPF #1 n Who or what are Ambler & Obiwan? n Object Persistence – Storage and retrieval of object data & object relationships n Multiple architectures – Single-tier, two-tier (client-server), multi-tier & internet enabled n Object Identity - All objects must be uniquely identified n Proxies or primary key objects – For performance optimisation and human navigation

Ambler, Obiwan & PWH’s requirements of an OPF #2 n Data as objects, or TDataSet – For use with reporting tools n Layering of application - Separation of Business Logic and User Interface n Several types of persistence mechanism – SQL databases, flat files, XML, legacy systems. n Various database versions and/or vendors.

Ambler, Obiwan & PWH’s requirements of an OPF #3 n Generic or native database drivers – Generic (ODBC, BDE, ADO) or native (DOA, IBX, MSDOM) n Multiple connections - Multiple connections to multiple databases in a thread safe way. n Transactions – Database transactions, and object – database transaction relationships Auto generated SQL and DBA optimised SQL 

What is an OPF? n What is an OPF? What do you expect from an OPF? n Demo of an OPF application. n Why build an OPF. RAD vs OPF. n Ambler, Jedi-Obiwan and my design requirements of an OPF. n Architecture of the tiOPF

Three layer architecture of the tiOPF n 1. Business objects layer: Manipulate data in the application as objects. Based on GoF’s Composite Pattern. n 2. Persistence layer: Persist objects to a variety of data stores including SQL-RDBMSs, XML, CSV. Based on GoF’s Visitor, Template Method and Adaptor Patterns. 3. Presentation layer: Provide a family of controls to simplify user interaction with the BOM 

The tiOPF can be configured in 5 ways n Single-tier, single user, files based application n Two-tier, client server application n Multi-tier, internet enabled application n HTML / browser based application System to system data pump application (We will look at three of these) 

Two-tier, client-server application Presentation Win32 Application PerMgr Mapps BOM to persistence plugin BOM Persistent Store (Database) PerPlugin Saves data to choosen database

Multi-tier, Internet enabled application PerMgr Mapps BOM to persistence plugin Win32 ApplicationServer app BOM PerMgr Mapps BOM to persistence plugin Presentation Persistent Store (Database) PerPlugin Saves data to choosen database PerPlugin Saves data using XML over HTTP

HTML, Browser based application Persistent Store (Database) Framework to map BOM into HTML or XML & XSL Presentation Web server Presentation Browser PerMgr Mapps BOM to persistence plugin PerPlugin Saves data to choosen database BOM

System to system, data pump application Win32 Application PerMgr Mapps BOM to persistence plugin BOM PerMgr Mapps BOM to persistence plugin Persistent Store ‘B’ (Database) PerPlugin Saves data to choosen database PerPlugin Saves data to choosen database Persistent Store ‘A’ (Database)

Steps to understanding this architecture n To achieve this architecture, we require: n An abstract business object model n A way of traversing the model n A swappable database connection layer n Some GUI controls to make building the presentation layer easier These will be developed in the next part: The core principles of the tiOPF 

Tutorial Topics n Part 1: What is an OPF? What can an OPF do for me? n Part 2: The core principles of the tiOPF. n Part 3: A worked example of using the tiOPF

A walk through of the framework source n Where to download: n How to install: n Directory structure Applications - In tiPerFramework project group 

A walk through the documentation n What is an OPF (chapter 1) n The Visitor pattern framework (chapter 2) n The Visitor and SQL databases (chapter 3) n Building an abstract BOM (chapter 4) n Installing the tiOPF (chapter 5) n A worked example (chapter 6) The Adaptor pattern and database independence (chapter 7) And now, a detailed look at chapter 2 

The core principles of the tiOPF Aim: To come up with a generic way of performing a family of related tasks on some objects in a list. The task we perform may be different depending on the internal state of each object. We may not perform any tasks at all, or we may perform multiple tasks on multiple list objects. (The Visitor Pattern framework) 

Tutorial Topics n Part 1: What is an OPF? What can an OPF do for me? n Part 2: The core principles of the tiOPF. n Part 3: A worked example of using the tiOPF

A worked example of using the tiOPF n Demonstration...

Source code on the web n The source from this presentation, and the latest version of the documentation n can be found at: n Peter Hinrichsen TechInsite Pty Ltd