An Interface Mechanism for Encapsulating Weaving in Class-based AOP SPLAT2007 An Interface Mechanism for Encapsulating Weaving in Class-based AOP Naoyasu Ubayashi (Kyushu Institute of Technology) Akihiro Sakai (Kyushu Institute of Technology) Tetsuo Tamai (University of Tokyo) March 12, 2007

Today’s my talk The notion of interface is important in module compositions. It is also important in AO weaving. We provide a new interface mechanism Weaving-interface. This introduces a new weaving mechanism based on component-and-connector architecture.

Image of our idea Concern weaving by connectors connector connector weaving I/F weaving I/F weaving I/F Concern Component (class) Concern Component (class) Concern Component (class) connector connector weaving I/F Concern weaving by connectors Concern Component (class)

Outline Motivation Weaving-interface & ccJava Example programs Implementation Related work Conclusion

1. Motivation

Interface in OOP A client of a class has only to be aware of methods exposed by an interface of the class. A class can be modified without being aware of the client if the class does not change the interface. interface component (class) programmer client of a class interface component (class) programmer

However, in AOP … It is not necessarily easy for a programmer to understand the overall behavior of a woven program because a weaving modifies the behavior of a method defined in a class.

Our approach A programmer who defines a weaving has only to be aware of weaving-interfaces. A programmer of the class can change its implementation without being aware of the client if the class conforms to its weaving-interfaces. Component weaving-interface component (class) programmer Connector Component programmer who connects components component (class) programmer

2. Weaving-interface & ccJava

Example --- Figure editor Component interface Shape { public void moveBy(int dx, int dy); } class Point implements Shape { int x, y; public int getX() { return x; } public int getY() { return y; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } public void moveBy(int dx, int dy) { x += dx; y += dy; class Line implements Shape { Point p1, p2; public Point getP1() { return p1; } public Point getP2() { return p2; } public void setP1(Point p1) { this.p1 = p1; } public void setP2(Point p2) { this.p2 = p2; } p1.x += dx; p1.y += dy; p2.x += dx; p2.y += dy; class Display { public static void update() { /* the detail is ommited */ } } Component compose three concern components - Point - Line - Display Component

AO weaving based on component-connector architecture export program points (update) wDisplay wPoint wLine class Display class Point class Line Component redraw import program points (at set*, moveBy) logging wLogging Connector class Logging Weaving-interface

ccJava --- a language for supporting weaving-interfaces ccJava: Class-based Crosscutting language for Java ccJava --- a language for supporting weaving-interfaces Weaving-interface public w_interface wPoint { pointcut change(): execution(void setX(int)) || execution(void setY(int)) || execution(void moveBy(int, int)); import before(), after() returning, around() : change(); } public w_interface wLine { execution(void setP1(Point)) || execution(void setP2(Point)) || public w_interface wDisplay { pointcut redraw(): execution(void update()); import before(), after() returning : redraw(); export redraw(); A class must implement methods or fields related exposed by pointcuts. Only the program points selected by pointcuts are target of weaving. Connector weave { class Point implements wPoint; class Line implements wLine; class Display implements wDisplay; connect(port1:wDisplay.redraw, port2:{wPoint || wLine}.change) { after() returning : port2 { port1.proceed(); } }

3. Example programs

Example (1) --- Method composition Weaving-interface Component public w_interface wColor { pointcut change() : execution(void setColor(int)); export change(); } public w_interface wPoint { pointcut change(): execution(void setX(int)) || execution(void setY(int)) || execution(void moveBy(int, int)); import before(), after() returning, around() : change(); weave { class Color implements wColor; class Point implements wPoint; connect(port1:wColor.change, port2:wPoint.change){ around() : port2 { port2.proceed(); port1.proceed();}} Color Point setX setY moveBy setColor behavioral composition Connector

Example (2) --- Inter-type declaration Weaving-interface Component public w_interface wColor { pointcut color_property() : field(int color) || method(void setColor(int))|| method(int getColor()); export color_property(); } public w_interface wColorPoint extends wPoint { pointcut thisClass() : class(this); import introduce() : thisClass(); weave { class Color implements wColor; class Point implements wColorPoint; connect(port1:wColor.color_property, port2:wColorPoint.thisClass) { introduce() : port2 from port1; } Color Point color setX setY moveBy setColor getColor structural composition Connector Point color setX setY moveBy setColor getColor

Example (3) --- Software evolution with ccJava version 1 version 2 Component Component class Point implements Shape { int x, y; public int getX() { return x; } public int getY() { return y; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } public void moveBy(int dx, int dy) { x += dx; y += dy; } class Point implements Shape { int x, y; public int getX() { return x; } public int getY() { return y; } public void setX(int x) { this.x = x; } public void setY(int y) { this.y = y; } public void moveByPlus (int dx, int dy) { x += dx; y += dy; } Connector weave { class Point implements wPoint replacing moveBy with moveByPlus; class Line implements wLine; class Display implements wDisplay; connect(port1:wDisplay.redraw, port2:{wPoint || wLine}.change){ after() returning : port2 { port1.proceed();}} } Weaving-interfaces do not have to be modified !

Example (4) --- Interface for dealing with multiple classes Weaving-interface public w_interface wChange { pointcut change(): execution(void set*(..)) || execution(void moveBy(int, int)); import before(), after() returning, around() : change(); } Connector weave { class Point implements wChange; class Line implements wChange; class Display implements wDisplay; connect(port1:wDisplay.redraw, port2:wChange.change){ after() returning : port2 { port1.proceed(); } } } The scope of the weaving impact is limited to classes that implement wChange. We have only to look at Point and Line.

4. Implementation

Compiler construction ccJava code (weaving-interface) Java code (class) ccJava parser ccJava compiler AspectJ code generator Aspect-Factory class generator AspectJ code (aspect) AspectJ weaver executable program

Generated code generated aspect generated factory class aspect wPoint { Display display = new DisplayFactory.getInstance(); pointcut change(): execution(void Point.setX(int)) || execution(void Point.setY(int)) || execution(void Point.moveBy(int, int)); after() returning: change() { display.update(); } } public class DisplayFactory { private static Display instance = new Display(); public static Display getInstance { return instance; generated factory class If a programmer wants to define a specific factory class, … weave { class Display implements wDisplay factory UserDefinedFactory; /* other definitions are omitted */ }

5. Related work

Related work Aspect-aware interface [Kiczales, et al. 2005] Open modules [Aldrich2005] Crosscutting programming interface (XPI) [Sullivan, et al. 2005]

Expressiveness for crosscutting descriptions NAW NOC NOC/NAW AspectJ 1 2 2 ccJava as an open module 2 2 1 ccJava using wildcard 1 2 2 NWA: number of aspects or weaving-interfaces NOC: number of classes

Traceability of weaving impact NOC IFW NOIF AspectJ 1 all aspects number of aspects AAIF(*) 1 AAIF 1 ccJava 1 weaving-I/Fs number of weaving-IFs * AAIF: Aspect-aware Interface number of all aspects > number of implemented weaving-IFs NOC: number of classes IFW: impact factors for weaving NOIF: number of impact factors

6. Conclusion

Conclusion A new interface mechanism Weaving-interface A new weaving mechanism based on component-and-connector architecture Flexible Weaving Mechanism !