PPL-summer09chiba

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あきひろしろみず
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1 OOP, AOP, PPL Summer School

2 2

3 Abstract Data Type CLU [Liskov 1977] typedef int point[2]; int getx(point p) { return point[0]; void rmove(point p, int dx, int dy) { p[0] += dx; p[1] += dy; 3

4 Object Simula, Smalltalk, CLOS, C++, Self, Dynamic dispatch Inheritance GUI killer app. 4

5 Multiple Inheritance? name(){ return A::name() + B ; Class B Class A Class C name(){ return A ; name(){ return A::name() + C ; name(){ return B::name() + C::name() + D ; Class D B D E 5

6 Mixin Or mixin Mixin instance Class A Class A Class B Class C Class B Class C Class D Class D 6

7 name() super.name() name(){ return A ; name(){ return super.name() + B ; Class B Class A Class C name(){ return super.name() + C ; name(){ return super.name() + D ; Class D 7

8 Mixin mixin mixin get() { return getx(); Class A mixin super getx() { return xpos; Class B Mixin C 8

9 Traits [2003] (fields) Require Java abstract? Traits traits Aliasing Exclusion( 9

10 super class class Position { int x, y; int getx(); class Traits class TCircle { require int getr(); int size() { return getr() * getr() * PI; class Circle extends Position uses TCircle { int r; int getr() { return r; trait 10

11 Flattening property Class = Superclass + State + Traits + Glue State, Traits, Glue Class Traits Traits 11

12 Glue code Multiple inheritance Mixin Glue code Composition Traits Glue code composition 12

13 Aspects [late 90 s] module decomposition Crosscutting concerns 13

14 Crosscutting concern Is a program hierarchically decomposed? implementing non-functional or functional concern 14

15 Logging (OOP/delegation) Logging code class Log { scattering in many classes Who instantiates Log? PrintStream output = System.out; void print(string msg) { output.println(msg); class Car extends Vehicle { Log log = ; void start() { log.print( start Car );... void goback() { log.print( Car goes back ); class Bike extends Vehicle{ Log log = ; void start() { log.print( start Bike );... 15

16 Instance-level composition Real Ideal? (hierarchical composition) Vehicle Log Vehicle Log Car Bike Log Log Car Bike Vehicle Car Vehicle Bike Vehicle Bike Log Vehicle Car Log Vehicle Bike 16

17 2 has-a is-a has-a delegation is-a class Pos { int x, y; int getx() { return this.x; class Pos3D { Pos p = new Pos(); int z; int getx() { return p.getx(); class Pos3D extends Pos { int z; int getx() { return super.getx(); 17

18 Delegation has-a JavaScript prototype prototype Java void move(int x, int y) { delegate.move(x, y); 18

19 Modular glue code All in one Vehicle Log Not possible: Tree separate components Car Bike Log Log Log Vehicle Vehicle Car Vehicle Bike Vehicle Bike Car Vehicle Bike

20 Crosscutting State-Share Not useful Is-a and Multiple inheritance Mixin, traits Has-a/part-of Vehicle Log Log Delegation? Composition (= writing glue code by hand) is annoying Car need syntax support like Traits? Vehicle Bike Vehicle Bike 20

21 Scattering Glue code Is scattering even if no crosscutting share. class Log { No modularity? Writing glue code is annoying PrintStream output = System.out; void print(string msg) { output.println(msg); class Car extends Vehicle { Log log = ; void start() { log.print( start Car );... void goback() { log.print( Car goes back ); class Bike extends Vehicle{ Log log = ; void start() { log.print( start Bike );... 21

22 Logging concern How a log message is printed Console, a log file, syslog server, Log.print() Which messages are in the same log Who share the Log object. When a log message is printed start(), goback(), What message is printed Start Car, Bike goes back, 22 Glue code

23 Glue code How to compose Delegation Shared state Mixin, Traits 23

24 Logging (AOP) Logging code aspect Log { in a single module with glue code instantiate this once call this print() before every method invocation PrintStream output = System.out; void print(string msg) { output.println(msg); class Car extends Vehicle { Log log = ; void start() { log.print( start Car );... void goback() { log.print( Car goes back ); class Bike extends Vehicle{ Log log = ; void start() { log.print( start Bike );... 24

25 Definition of an aspect Logging aspect in AspectJ Turning logging on/off does not need source code modification. aspect Logging issingleton { PrintStream output = System.out; before(): execution(* Vehicle+.*(..)){ output.println(thispointcut.tostring()); 25

26 Glue code in AOP (1) Glue code Shared states aspect Car Bike glue code pointcut logging, transaction, security, 26

27 Glue code in AOP (2) Glue Aspect 2 Abstract aspect Glue code sub-aspect Traits states super aspect 27

28 Logging (AOP+inheritance) aspect Log { PrintStream output = System.out; void print(string msg) { output.println(msg); aspect VehicleLog extends Log { instantiate this once call this print() before every method invocation class Car extends Vehicle { Log log = ; void start() { log.print( start Car );... void goback() { log.print( Car goes back ); class Bike extends Vehicle{ Log log = ; void start() { log.print( start Bike );... 28

29 non-invasive (oblivious) Glue code Shared states aspect Car Bike (?) Car Bike Car Bike Car EcoCar new Car() new EcoCar() 29

30 mixin traits AOP with non-invasiveness Classbox 30

31 Application of AOP JastAdd in Java Aspect Lexical analyer, parser, code generator 1 Java 1.4 Java 1.5 Java 1.5 AspectJ 31

32 Limitations of AOP Crosscutting concerns are real. not only logging but functional extensions AspectJ is not the best. Fragile pointcut problem Too powerful glue code, no static check Interferences between multiple aspects No explicit control of composition Breaking encapsulation? Maintainability is low Invasiveness 32

33 Modularity v.s. (non-invasiveness) 1 modular? JastAdd Modularity? Separate compilation aspect 33

34 Partial classes of C# Non-invasive extension A class declaration can be divided into multiple partial declarations. public partial class Position { int x; public partial class Position { int y; A compiler lexically merges them. no modular compilation. Categories of Objective-C are similar but allow modular compilation by including header files. 34

35 Open classes [oopsla 00] Non-invasive extension allows adding a new method to an existing class. Top-level method declarations public boolean Node.typeCheck() { similar to intertype declarations of AspectJ Access control only non-private methods are accessible. Modularly type-checkable no top-level method for interfaces or top-level abstract method 35

36 Feature-Oriented Programming Feature feature AHEAD tool Program = f(g(h( k(c) ))) f, g, h, k: feature c: (non-invasive) like mixin, open classes, intertype declaration, 36

37 Context-Oriented Programming (contexts) dynamic scope class Position { int x, y; void move(int dx, int dy) { foo(position p) { p.move(3, 4); aspect A { void Position.move(..) { proceed(); bar () { Position p = ; foo(p); deploy(a) { foo(p); 37

38 Context-Oriented Programming (contexts) : non-invasive as in AOP within, cflow pointcut conditionally activate an advice dynamic deploy conditionally activate an aspect 38

39 glue code Glue code mixin traits AOP FOP COP 39

1 Dependency Injection glue glue glue glue glue GluonJ GluonJ glue Dependency Injection Aspect-Oriented Programming Meets Dependency Injection Rei Ish

1 Dependency Injection glue glue glue glue glue GluonJ GluonJ glue Dependency Injection Aspect-Oriented Programming Meets Dependency Injection Rei Ishikawa and Shigeru Chiba This paper proposes programming