1. The document discusses applying architectural patterns and principles like logging, validation, transactions, and exception handling to business logic code in .NET. 2. It shows an example of refactoring a method that rents a book to a customer to add logging, validate method parameters, retry transactions using a scope, and handle exceptions. 3. By applying these techniques, the business logic is made more robust, maintainable, and aligned with best practices for .NET development.

1. AOP mit .NET
12.04.2012
Dipl.-Inf. (FH) Johannes Hoppe

2. Johannes Hoppe
ASP.NET MVC Webentwickler
www.johanneshoppe.de

3. 01
Architektur und Patterns

4. Patterns
software craftsmanship

5. Business Code
public class CustomerProcesses
{
public void RentBook( int bookId, int customerId )
{
Book book = Book.GetById( bookId );
Customer customer = Customer.GetById( customerId );
book.RentedTo = customer;
customer.AccountLines.Add(
string.Format( "Rental of book {0}.", book ), book.RentalPrice
);
customer.Balance -= book.RentalPrice;
}
}

6. Business Code

8. Business Code
public class CustomerProcesses
{
public void RentBook( int bookId, int customerId )
{
Book book = Book.GetById( bookId );
Customer customer = Customer.GetById( customerId );
book.RentedTo = customer;
customer.AccountLines.Add(
string.Format( "Rental of book {0}.", book ), book.RentalPrice
);
customer.Balance -= book.RentalPrice;
}
}

9. Business Code
+ Logging
internal class CustomerProcesses
{
private static readonly TraceSource trace =
new TraceSource( typeof (CustomerProcesses).FullName );
public void RentBook( int bookId, int customerId )
{
trace.TraceInformation(
"Entering CustomerProcesses.CreateCustomer( bookId = {0},
customerId = {1} )",
bookId, customerId );
try
{
Book book = Book.GetById( bookId );
Customer customer = Customer.GetById( customerId );
book.RentedTo = customer;
customer.AccountLines.Add(
string.Format( "Rental of book {0}.", book ), book.RentalPrice );
customer.Balance -= book.RentalPrice;
trace.TraceInformation(
"Leaving CustomerProcesses.CreateCustomer( bookId = {0}, customerId = {1} )",
bookId, customerId );
}
catch ( Exception e )
{
trace.TraceEvent( TraceEventType.Error, 0,
"Exception: CustomerProcesses.CreateCustomer(
bookId = {0}, customerId = {1} ) failed : {2}",
bookId, customerId, e.Message );
throw;
}
}
}

10. Business Code
+ Logging
internal class CustomerProcesses
+ Vorbedingungen {
private static readonly TraceSource trace =
new TraceSource(typeof(CustomerProcesses).FullName);
public void RentBook(int bookId, int customerId)
{
if (bookId <= 0) throw new ArgumentOutOfRangeException("bookId");
if (customerId <= 0) throw new ArgumentOutOfRangeException("customerId");
trace.TraceInformation(
"Entering CustomerProcesses.CreateCustomer( bookId = {0}, customerId = {1} )",
bookId, customerId);
try
{
Book book = Book.GetById(bookId);
Customer customer = Customer.GetById(customerId);
book.RentedTo = customer;
customer.AccountLines.Add(string.Format("Rental of book {0}.", book),
book.RentalPrice);
customer.Balance -= book.RentalPrice;
trace.TraceInformation(
"Leaving CustomerProcesses.CreateCustomer( bookId = {0},
customerId = {1} )“, bookId, customerId);
}
catch (Exception e)
{
trace.TraceEvent(TraceEventType.Error, 0,
"Exception: CustomerProcesses.CreateCustomer( bookId = {0},
customerId = {1} ) failed : {2}",
bookId, customerId, e.Message);
throw;
}
}
}

11. Business Code
+ Logging + Transaktionen
+ Vorbedingungen
internal class CustomerProcesses ts.Complete();
{ }
private static readonly TraceSource trace =
new TraceSource(typeof(CustomerProcesses).FullName); break;
}
public void RentBook(int bookId, int customerId) catch (TransactionConflictException)
{ {
if (bookId <= 0) if (i < 3)
throw new ArgumentOutOfRangeException("bookId"); continue;
if (customerId <= 0) else
throw new ArgumentOutOfRangeException("customerId"); throw;
}
trace.TraceInformation( }
"Entering CustomerProcesses.CreateCustomer( bookId = {0},
customerId = {1} )“, bookId, customerId); trace.TraceInformation(
"Leaving CustomerProcesses.CreateCustomer(
try bookId = {0}, customerId = {1} )",
{ bookId, customerId);
for (int i = 0; ; i++) }
{ catch (Exception e)
try {
{ trace.TraceEvent(TraceEventType.Error, 0,
using (var ts = new TransactionScope()) "Exception: CustomerProcesses.CreateCustomer( bookId = {0},
{ customerId = {1} ) failed : {2}",
Book book = Book.GetById(bookId); bookId, customerId, e.Message);
Customer customer = throw;
Customer.GetById(customerId); }
}
book.RentedTo = customer;
customer.AccountLines.Add( }
string.Format("Rental of book {0}.", book),
book.RentalPrice);
customer.Balance -= book.RentalPrice;

12. Business Code
+ Logging + Transaktionen
+ Vorbedingungen + Exception Handling
internal class CustomerProcesses
{ ts.Complete();
private static readonly TraceSource trace = }
new TraceSource(typeof(CustomerProcesses).FullName);
break;
public void RentBook(int bookId, int customerId) }
{ catch ( TransactionConflictException )
if (bookId <= 0) throw new ArgumentOutOfRangeException("bookId"); {
if (customerId <= 0) if ( i < 3 )
throw new ArgumentOutOfRangeException("customerId"); continue;
else
try throw;
{ }
trace.TraceInformation( }
"Entering CustomerProcesses.CreateCustomer(
bookId = {0}, customerId = {1} )", trace.TraceInformation(
bookId, customerId ); "Leaving CustomerProcesses.CreateCustomer(
bookId = {0}, customerId = {1} )",
try bookId, customerId );
{ }
for ( int i = 0;; i++ ) catch ( Exception e )
{ {
try trace.TraceEvent( TraceEventType.Error, 0,
{ "Exception: CustomerProcesses.CreateCustomer(
using ( var ts = new TransactionScope() ) bookId = {0}, customerId = {1} ) failed : {2}",
{ bookId, customerId, e.Message );
Book book = Book.GetById( bookId ); throw;
Customer customer = Customer.GetById( customerId ); }
}
book.RentedTo = customer; catch ( Exception e )
customer.AccountLines.Add( {
string.Format( "Rental of book {0}.", book ), if (ExceptionManager.Handle(e)) throw;
book.RentalPrice ); }
customer.Balance -= book.RentalPrice; }

13. Business Code
+ Logging + Transaktionen
+ Vorbedingungen + Exception Handling
+ Feature X
+ Feature Y
+ Feature Z
+…

14. Kern- Seperation
funktionalitäten of Concerns
(Core Concerns)

15. VS

16. VS
Nicht-
Funktionale
Anforderungen
(Crosscutting Concerns)

17. Cross-Cutting Concerns
Security Data Binding
Exception Handling Thread Sync
Tracing Caching
Monitoring Validation
Transaction …

18. OOP
OOP
+ AOP

19. Spring.NET
PostSharp LinFu Castle
MS Unity
Build-Time Hybrid Run-Time

20. Build-Time: “Statisch” Run-Time: “Dynamisch”
Erfolgt bei Kompilierung Erfolgt zur Laufzeit
Code wird direkt verändert Code bleibt unverändert
Zur Laufzeit keine Änderungen Zur Laufzeit Änderungen möglich
Auch auf Properties, Felder, Aufruf wird über Proxy
Events anwendbar umgeleitet
Keine Interfaces erforderlich idR. Interfaces erforderlich (Proxy)

21. 02
Live Coding

23. Logging
LogTimeAspect
webnoteaop.codeplex.com

24. Exceptions
ConvertExceptionAspect
webnoteaop.codeplex.com

25. Validierung
ValidationGuardAspect
webnoteaop.codeplex.com

26. Caching
SimpleCacheAspect
webnoteaop.codeplex.com

28. 03
AOP 1 x 1

29. AspectJ Begriffe
Join Point
Pointcut
Advice
Aspect

30. AspectJ Begriffe
Join Point
Pointcut
Advice
Aspect

31. IL Code Vorher
[LogTimeAspect]
public ActionResult Index()
{
IEnumerable<NoteWithCategories> notes =
this.WebNoteService.ReadAll();
return View(notes);
}

32. IL Code Nachher
public ActionResult Index()
{
ActionResult CS$1$2__returnValue;
MethodExecutionArgs CS$0$3__aspectArgs =
new MethodExecutionArgs(null, null);
<>z__Aspects.a68.OnEntry(CS$0$3__aspectArgs);
try
{
IEnumerable<NoteWithCategories> notes =
this.WebNoteService.ReadAll();
ActionResult CS$1$0000 = base.View(notes);
CS$1$2__returnValue = CS$1$0000;
}
finally
{
<>z__Aspects.a68.OnExit(CS$0$3__aspectArgs);
}
return CS$1$2__returnValue;
}

33. Originale Methode Aspekt Klasse
OnEntry
try
{
Method Body
OnSuccess
}
catch (Exception e)
{
OnException
}
finally
{
OnExit
}
: OnMethodBoundaryAspect

34. 04
Installation

35. www.sharpcrafters.com/postsharp/download

36. nuget
http://nuget.org/packages/PostSharp

37. Spring.NET PostSharp
springframework.net sharpcrafters.com
Castle Demo Download
castleproject.org webnoteaop.codeplex.com
Unity
unity.codeplex.com

38. FRAGEN?

39. Bis bald
› 10.05.2012 – .NET UG Karlsruhe: NoSQL
› 14.05.2012 – .NET Developer Conference (DDC)
.Nürnberg: NoSQL

40. Vielen Dank!

41. Primitive Aspekt-Typen
› MethodBoundaryAspect › LocationInterceptionAspect
› OnEntry › OnGetValue
› OnSuccess › OnSetValue
› OnException
› OnExit › EventInterceptionAspect
› OnAddHandler
› OnExceptionAspect › OnRemoveHandler
› OnException › OnInvokeHandler
› MethodInterceptionAspect › MethodImplementationAspect
› OnInvoke › OnInvoke
› CompositionAspect
› CreateImplementationObject

42. Bildnachweise
Ausgewählter Ordner © Spectral-Design – Fotolia.com
Warnhinweis-Schild © Sascha Tiebel – Fotolia.com
Liste abhaken © Dirk Schumann – Fotolia.com
3D rendering of an architecture model 2 © Franck Boston – Fotolia.com
Healthcare © ArtmannWitte – Fotolia.com
Stressed businessman © Selecstock – Fotolia.com
Funny cartoon boss © artenot – Fotolia.com