Programming AspectJ with Eclipse and AJDT, By Example. Chien-Tsun Chen Sep. 21, 2003

Transcription

1 Programming AspectJ with Eclipse and AJDT, By Example Chien-Tsun Chen Sep. 21, 2003

2 References R. Laddad, I want my AOP!, Part 1-Part3, JavaWorld, R. Laddad, AspectJ in Action, Manning, T. Elrad et. al, Discussing Aspects of AOP, Commun. ACM 44, 10(Oct. 2001). G. Kiczales et, al, Getting Started with AspectJ, Commun. ACM 44, 10(Oct. 2001). The AspectJ Programming Guide, by the AspectJ Team

3 Outline Introduction to Aspect-Oriented Programming (AOP) Eclipse and AspectJ Development Tools (AJDT) Programming AspectJ, By Example Q&A

4 Introduction to AOP

5 Concerns and AOP A concern is a particular goal, concept, or area of interest. In technology terms, a typical software system comprises several core and system-level concerns. AOP better separates concerns than pervious methodologies, thereby proving modularization of crosscutting concerns.

6 View the system as a set of concerns

7 Concern decomposition

8 Crosscutting concerns in a system We can broadly classify requirements as core module-level requirements and system-level requirements : System-level requirements tend to be mutually independent to each other and to the module-level requirements. System-level requirements also tend to crosscut many core modules. An Example.

9 Crosscutting concern problems The requirement space is an n-dimensional space, whereas the implementation space is one-dimensional (tends to be the core module-level implementation, and the remaining requirements are tagged along this dominant dimension). Such a mismatch results in an awkward requirements-to-implementation map.

10 Symptoms Code tangling. Code scattering.

11 Implications Poor traceability. Lower productivity. Less code reuse. Poor code quality. More difficult evolution.

12 The current response: defer a concern s final implementation Mix-in classes: The primary class contains a mix-in class instance and allows the system;s other parts to set that instance. Problem: Control flow stays with the main class. Design patterns: Behavioral design patterns, like Visitor and Template Method. Problem: Control flow stays with the main class. Domain-specific solutions: Frameworks and application servers (EJB Server). XML-based mapping descriptor.

13 The fundamentals of AOP OOP creates systems using loosely coupled, modularized implementations of common concerns. Modularization unit: Class. AOP creates systems using loosely coupled, modularized implementations of crosscutting concerns. Modularization unit: Aspect.

14 Three distinct development steps of AOP Source code weaver Byte code weaver Just-in-time weaver

15 AOP benefits Modularized implementation of crosscutting concerns. Easier-to-evolve systems. Late binding of design decisions. More code reuse.

16 Eclipse and AJDT

17 Eclipse- An universal tool platform (adapted from Eclipse in Action) (ex, AJDT, CDT)

18 AJDT The AspectJ Development Tools (AJDT) project will provide Eclipse platform based tool support for Aspect-Oriented Software Development (AOSD) with AspectJ. Their goal is to deliver a user experience that is consistent with the Java Development Tools (JDT) when working with AspectJ projects and resources.

19 Programming AspectJ, By Example

20 What is AspectJ AspectJ, a freely available AOP implementation for Java from Xerox PARC, is a general-purpose aspectoriented Java extension. Current version: 1.1.

21 Five main elements to modularize crosscutting concerns A joint point model describing the hooks where enhancements may be added. joint point. A means of identifying join points. pointcut (selects join points and collects context at those point). A means of specifying behavior at join points. advice (before, after, and around). Encapsulated units combining join point specifications and behavior enhancements. aspect. A method of attachment of units to a program. aspect weaver.

22 How to Apply AOP in Your Work: Two Types of Aspects Development Aspects: Tracing, profiling and logging, pre- and post-conditions, contract enforcement, and configuration management. Production Aspects: Change monitoring, context passing and providing consistent behavior.

23 My Examples (1/3) GOF s Design Patterns: Singleton Pattern: Step 1: Display (non-singleton) Step 2: DisplaySingleton Step 3: SingletonAspect Observer Pattern (next time).

24 My Examples (2/3) Users Defined Compile-Time Errors and Warring. Context Compile-Time Warning Compile-Time Errors Introduction New Type

25 My Examples (3/3) Pointcut Parameters. HandleLiveness. DeadPartnerException Wake partner up Design By Contract An Eiffel example A Java example (without DBC) A Java example (with DBC) A AspectJ example (with DBC)

26 Tools Support Eclipse (AJDT 1.1.3) Emacs JDEE NetBeans JBuilder

27 Q&A

28 What are the problems?

29 Singleton Example: Step 1 (1/3)

30 Singleton Example: Step 1 (2/3) 1 2 3

31 Singleton Example: Step 1 (3/3) 1 2 3

32 Singleton Example: Step 2 (1/3) 1 2 3

33 Singleton Example: Step 2 (2/3) 1 2 3

34 Singleton Example: Step 2 (3/3) 1 2 3

35 Singleton Example: Step 3 (1/3) keyword Pointcut name Pointcut type Signature patterns

36 Singleton Example: Step 3 (2/3) 1 2 3

37 Singleton Example: Step 3 (3/3) 1 2 3

38 Compile-Time Errors and Warring: Context edu.ntut.csie edu.ntut.csie.service Two Packages 1 syncnow is deprecated, Use syncnow2 instead. FileSync +syncnow() +syncnow2() 2 SMTP +start() +stop() Can compiler tell us such information in compile time? MyWWW +start() +stop() WWW +start() +stop() Tester +main() DeprecatedAspect <<Aspect>> ErrorAspect <<Aspect>> Classes in package edu.ntut.csie.service and their subclass (may or may not in the same package) cannot create classes or call methods of java.awt.component and it s subclasses.

39 Compile-Time Warning (1/2) 1 2 3

40 Compile-Time Warning (2/2)

41 Compile-Time Errors (1/6) 1 2 3

42 Compile-Time Errors (2/6) 4 5

43 Compile-Time Errors (3/6)

44 Compile-Time Errors (4/6)

45 Compile-Time Errors (5/6)

46 Compile-Time Errors (6/6)

47 Introduction New Type (1/2)

48 Introduction New Type (2/2) 1 2 3

49 Pointcut Parameters

50 HandleLiveness: DeadPartnerException (1/2) 1 2 3

51 HandleLiveness: DeadPartnerException (2/2)

52 HandleLiveness: Wake Partner Up (1/2) 1 2 3

53 HandleLiveness: Wake Partner Up (2/2)

54 DBC: An Eiffel Example (1/2) 3 4 has (k: KEY): BOOLEAN 1 2

55 DBC: An Eiffel Example (2/2) 1 2

56 A Java Example, without DBC

57 A Java Example, with DBC (1/3)

58 A Java Example, with DBC (2/3)

59 A Java Example, with DBC (3/3) 1 2 core concern 3 Code tangling?

60 DBC: A AapectJ Example (1/4)

61 DBC: A AapectJ Example (2/4)

62 DBC: A AapectJ Example (3/4) Is this right?

63 DBC: A AapectJ Example (4/4) Access private data members, not so good.

64 Eclipse with AspectJ (1/4)

65 Eclipse with AspectJ (2/4)

66 Eclipse with AspectJ (3/4)

67 Eclipse with AspectJ (4/4)

68 AspectJ-aware extension to emacs