Ieg3080 Tutorial 11 Prepared By Ryan Outline  Enterprise

IEG3080 Tutorial 11 Prepared by Ryan

Outline  Enterprise  

Application Architecture

Layering Structure Domain Logic

 C#

Attribute

 Aspect

Oriented Programming (AOP)

Enterprise Application Architecture  Complex

systems always break down into

layers  

e.g. Networking – OSI 7 layers Model Pros 





Working on a single layer without knowing much about other layers Minimizing dependencies between layers

Con 

Transforming from layers harming performance

Enterprise Application Architecture  Enterprise 

Presentation Layer  



Display of information e.g. GUI windows, webpage Handling user commands

Domain Logic Layer 



Application Architecture – 3-layer

Business logic (Core)

Data Source Layer 

Communication with database, messaging systems

Enterprise Application Architecture  Domain 

Logic Patterns

Domain Model 

An object model of the domain that incorporates both behavior and data 

 

Solving the problem in object-oriented way

Pro – Handling complex logic in a well-organized way Con – “Impedance mismatch” between OO model and relational database

Enterprise Application Architecture  O/R 





Mapping Problems – Identity Problem

OO – Different objects referenced by different pointers Database – Different rows identified by primary key Solutions 

Identity Field Team ID

Key Identity Field

Team Name

public class Team { int TeamID; string TeamName; }

Enterprise Application Architecture  O/R 

Mapping Problems – Identity Problem

Solutions (Cont’d) 

Foreign Key Mapping Team

Player

1

Team ID

Player ID

*

Team Name

Team ID

Team Name

Player ID

Team ID

Player Name

Player Name

Foreign Key Mapping

Enterprise Application Architecture  O/R

Mapping Problems – Inheritance Student Name

How to do mapping?

School

Secondary Student

University Student

Class

Department

CUHK Student College

Enterprise Application Architecture  O/R 

Mapping Problems – Inheritance

Single Table Inheritance Name





School

Class

Department

College

Wasting space – many null columns

Concrete Table Inheritance



Name

School

Class

Name

School

Department

Name

School

Department

College

Changing the superclass  altering all the subclasses’ tables

Enterprise Application Architecture  O/R 

Mapping Problems – Inheritance

Class Table Inheritance Name

School

Class Department College



Requiring multiple joins to rebuild an object

Enterprise Application Architecture  Solutions 

OO databases 





Not common (relational databases are widely adopted) Tight coupling with the domain model

Automated O/R mapping tools  

Not prefect (may solve 80% of the problems) Expensive

Enterprise Application Architecture  Other 

Transaction Scripts 

Organizes business logic by procedures where each procedure handles a single request from the presentation 



Domain Logic Patterns

Server page (php, jsp), CGI scripts

Table Module 

A single instance that handles the business logic for all rows in a database table or view 

Commonly use in .NET development platform

C# Attribute  C#  

Attribute

Embedding information in C# code Placed in square brackets [ ], above an Attribute Target (e.g. class, field or method) [serializable] public class Test { … }

 Reflection  

Querying information at run-time Dynamically invoking methods

C# Attribute  Intrinsic 



Attribute

Built-in attributes in .NET Common Library Runtime (CLR) Examples 

In your assignment 1 

 

[assembly: AssemblyVersion(“1.0.0.0”)]

[serializable] [STAThread]

C# Attribute  Custom

Attribute

Create your custom attribute

Use your custom attribute

// Set what kinds of elements can use this custom attribute [AttributeUsage(AttributeTargets.All)] public class MyAttribute : Attribute { // Define your own attribute string myName;

[MyAttribute("MyClass")] public class Test { [MyAttribute("MyMethod")] public void Print { Console.WriteLine("Test Program"); } }

public MyAttribute(string name) { myName = name; } public string Name { get { return myName; } } }

C# Attribute  Reflection

– Querying information

public class MyProgram { public static void Main() { Type type = Type.GetType("Test"); foreach (Attribute attr in type.GetCustomAttributes(false)) { // Retrieve attributes for the class MyAttribute myattr = attr as MyAttribute; if (myattr != null) Console.WriteLine(attr.Name); } foreach(MethodInfo method in type.GetMethods()) { foreach (Attribute attr in method.GetCustomAttributes(false)) { // Retrieve attributes for the method MyAttribute myattr = attr as MyAttribute; if (myattr != null) Console.WriteLine(“Method: {0} with Attribute: {1}”, method, attr.Name); } } } }

Output MyClass Method: Void Print() with Attribute: MyMethod

C# Attribute  Reflection

– Invoking methods

public class MyProgram2 { public static void Main() { Type type = Type.GetType("Test"); Object o = Activator.CreateInstance(type); // Create a “type” object MethodInfo mi = type.GetMethod("Print"); mi.Invoke(o, null); // Invoke method - “mi” } }

Output Test Program

Aspect Oriented Programming  OOP  



Breaking down a complex system into modules Encapsulating responsibilities into different objects Problems 

Some tasks cut across multiple modules (crosscutting concern)  



Logging Authentication

Solution: Aspect Oriented Programming (AOP)

Aspect Oriented Programming  AOP

in C#

Non-AOP Implementation

AOP Implementation

public class Test { public void TestMethod() { Log log = new Log(); log.Print("Enter"); // Log when entering this method Console.WriteLine("Test Method"); log.Print("Leave"); // Log with leaving this method } }

[AttributeUsage(AttributeTargets.Class)] public class LogAttribute : ContextAttribute { // Code Here } public class LogProperty : IContextProperty, IContributeObjectSink { // Code Here } public class LogAspect : IMessageSink { // Code Here } [Log] public class Test : ContextBoundObject { public void TestMethod() { Console.WriteLine("Test Method"); } }

Aspect Oriented Programming  How  

does it work in C#

“ContextAttribute” and “ContextBoundObject” Intercepting the calls(Interception) Client

YourObject Without Interception Intercepted by .NET

Client

Transparent Proxy

Message Sink

With Interception

YourObject

References  Enterprise 

M. Fowler, “Patterns of Enterprise Application Architecture”, Addison Wesley

 C# 

Attribute

http://www.oreilly.com/catalog/progcsharp/chapter/ch1

 Aspect  

Application Architecture

Oriented Programming (AOP)

http://www.codeproject.com/gen/design/aop.asp http://msdn.microsoft.com/msdnmag/issues/02/03/AOP