Features Meet Aspects Software Development with. 2 Motivation for CaesarJ … OO languages lack...

Features Meet Aspects Software Development with

2

Motivation for CaesarJ …

• OO languages lack support for:– Higher-level modules beyond classes to capture features– Crosscutting composition of features

• AO languages have support for crosscutting composition– But they poorly support feature modularization and

refinement

3

Higher-Level Modules ...

• Existing languages lack sufficient means for organizing collaborating classes– e.g., packages and namespaces

• Problems– no means to express variants of a collaboration– no polymorphism– no runtime semantics

• Mechanisms that proved useful for single classes not available for sets of collaborating classes

4


Example: a component for displaying hierarchical structures getRoot()

generateLayout()draw(g)refresh()

HierarchyDisplay

getText()textFits(text)calculateLayout()initShape(pt)draw(g)

shape: Shape

Node

getChildAt(int)getChildCount()calculateLayout()draw(g)

CompositeNode

init(parent, child)initShape(pt)draw(g)

conn: Connector

Connection

0-*connections

parent

child

0-*

children… can you imagine putting it into one class-like module?

5


… can you imagine extending the hierarchy display component … by overriding only affected classes,

… just as one extends single classes by overriding affected methods?

getRoot()generateLayout()draw(g)refresh()

HierarchyDisplay

getText()textFits(text)calculateLayout(..)positionNode(..)initShape(..)draw(g)

shape: Shape

Node


CompositeNode


conn: Connector

Connection

0-*connections

parent

child

0-*

children

AdjustedHierarchyDisplay

textFits(text)positionNode(..)

maxWidth: int

Node

CompositeNode

Connection

0-*connections

parent

child

0-*

children

6

C1

C2 C3

C4

C5

P1

P2

P3

C1

C3

C2

C4

APPL 1 APPLn

with a family of applications in a

domain

generic component

Crosscutting Composition …

7

getCEO()getDepartmentAt()getDepartmentCount()addDepartment()appointCEO()exchangeRoles()

Company

getDepartment()getFullName()getRole()getSex()assignTo()leaveDepartment()setRole()

namerolesex

Employee

getManager()getName()getWorkerAt()getWorkerCount()appointManager()registerWorker()unregisterWorker()

name

Department

0-*

ceo11 manager

0-*

1

workers

CompanyModel HierarchyDisplay

getRoot()generateLayout()

draw(g)refresh()

getText()

textFits(text)calculateLayout()

initShape(pt)draw(g)

shape: Shape

Node

getChildAt(int)getChildCount()calculateLayout()

draw(g)

CompositeNode

init(parent, child)initShape(pt)

draw(g)

conn: Connector

Connection

0-*connections

parent

child

children

Crosscutting Composition ...

… want to use for displayng a company’s structure …

CEO

Department Managers

Workers

and for a window’s structure …

8

Aspects of Crosscutting Composition

Company

Employee

Department

0-*

ceo1 1 manager

0-*

1

workers

adopt generic display logic for company model

after certain changes refresh display or recalculate layout

behavioral mapping needed

behavioral mapping needed


HierarchyDisplayImpl


Node


CompositeNode


Connection

0-*connections

parent

child

0-*

children

structural mapping needed

structural mapping needed

Let us try patterns …

9

Patterns for Integration…

getRoot()draw()setView()refresh()generateLayout()

view : JComponent

HierarchyDisplay

Adapters

getRoot()

root : Company

CompanyHierarchyDisplay

getText()getChildAt()getChildCount()

wrappee : Company

CompanyNode


wrappee : Department

DepartmentNode

getText()

wrappee : Employee

EmployeeNode


shape: Shape

Node


CompositeNode

Company EmployeeDepartment0-*

ceo 11manager

0-*1

workerscast down toCompanyNode

cast down toEmployeeNode

cast down toDepartmentNode

10

Patterns for Integration…

Observers

getRoot()companyChanged()departmentChanged()departmentRemoved()workerAdded()workerRemoved()employeeChanged()

root : Company


addObserver()removeObserver()

observers

Company


observers

Employee


observers

Department

0-*

ceo 1

1manager

0-*1

workers

employeeChanged()

EmployeeObserver

departmentChanged()workerAdded()workerRemoved()

DepartmentObserver

companyChanged()deparmentAdded()departmentRemoved()

CompanyObserver

0-* 0-*

0-*

11

CaesarJ in a Nutshell …

Component A

A B

C D

Component B

E F

G… beyond “typical crosscutting concerns“ (security, persistence …)

… focus on feature modularization, extension and integration

aspects and features inside

12

OutlineOutline

► Multi-class modules and hierarchical refinementsMulti-class modules and hierarchical refinements Defining and extending components with virtual Defining and extending components with virtual

classesclasses Hierarchical compositionHierarchical composition

► Crosscutting compositionCrosscutting composition Defining wrapper classesDefining wrapper classes Observing events with pointcutsObserving events with pointcuts Aspects as classesAspects as classes Dynamic aspect deploymentDynamic aspect deployment Variability managementVariability management

► State of the artState of the art

13

Virtual Classes

• Originates in Beta [Madsen et al]

• Idea:

Give inner classes the same status as (virtual) methods

Overriding and late binding should also apply to nested classes, similarly to overriding and late binding of methods.

• Consequence:

Virtual classes are properties of objects of the enclosing class– Talk about class expr.C, similarly to method expr.m()

14

Virtual Classes - Examplecclass HierarchyDisplayImpl { cclass Node {} cclass CompositeNode extends Node { ... } cclass Connection { void positionNode() {...} } void foo(Node n) { Connection c = new Connection(); }}

cclass HierarchyDisplayImplA extends HierarchyDisplayImpl { cclass Node { int maxwidth; ... } void foo(Node n) { … n.maxwidth … }}

cclass HierarchyDisplayImplB extends HierarchyDisplayImpl { cclass Connection { void positionNode() { … super.positionNode(); …} }}

15

Virtual Classes - Examplecclass HierarchyDisplayImpl { cclass Node {} cclass CompositeNode extends this.Node { ... } cclass Connection { void positionNode() {...} } void foo(this.Node n) { this.Connection c = this.new Connection(); }}

cclass HierarchyDisplayImplA extends HierarchyDisplayImpl { cclass Node extends super.Node { int maxwidth; ... } void foo(this.Node n) { … n.maxwidth … }}

cclass HierarchyDisplayImplB extends HierarchyDisplayImpl { cclass Connection extends super.Connection { void positionNode() { … super.positionNode(); …} }}

Implicit Scoping!

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Virtual Classes - Example

…if instance of HierarchyDisplayImplA

cclass HierarchyDisplayImpl { cclass Node {} cclass CompositeNode extends this.Node { ... } cclass Connection { void positionNode() {...} } void foo(this.Node n) { this.Connection c = this.new Connection(); }}



17


…if instance of HierarchyDisplayImplB




18


No type cast necessary




19

Composition of ExtensionsHierarchyDisplayImpl

Node

CompositeNode

Connection

0-*connections

parent

child 0-*

children

HierarchyDisplayImplA

Node

CompositeNode

Connection

0-*connections

parent

child 0-*

children

HierarchyDisplayImplB

Node

CompositeNode

Connection

0-*connections

parent

child 0-*

children

HierarchyDisplayImplAB

Node

CompositeNode

Connection

0-*connections

parent

child 0-*

children

• Can compose classes via „&“ operator

• Class composition via mixin linearization

cclass HierarchyDisplayAB extends HierarchyDisplayA & HierarchyDisplayB

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Propagating Mixin Composition

• Class composition and virtual classes interact by means of their respective influence/dependency on this and super.

– Composition: this refers to the composed class, super is determined by mixin linearization.

– Virtual Classes: All virtual type annotations are declared via the enclosing this and super, respectively.

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Composition of Layers

HdB.Node

Hd.CompNodeHd.Connection

CompNode NodeConnection

HdA.Connection

Hd.Node

cclass HierarchyDisplayImplAB extends HierarchyDisplayImplA & HierarchyDisplayImplB {}

22

Composition of Layers

HdB.Node

Hd.CompNodeHd.Connection

CompNode NodeConnection

HdA.Connection

Hd.Node

cclass HierarchyDisplayImplAB extends HierarchyDisplayImplA & HierarchyDisplayImplB {}

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Family Polymorphism

• Subclasses are subtypes!

hd.Node findChild(final HdI hd, hd.CompositeNode n, String str) { for (int i = 0; i < n.getChildCount(); i++) hd.Node m = n.getChildAt(i); if (m.getText().equals(str)) return m; } return null;}...

final HierachyDisplayA hda = new HierarchyDisplayA();hda.CompositeNode cna = …;

final HierachyDisplayB hdb = new HierarchyDisplayB();hdb.CompositeNode cnb = …;

hda.Node n = findChild(hda, cna, someString); // okhdb.Node n = findChild(hdb, cnb, someString); // okhda.Node n = findChild(hdb, cna, someString); // static error

24

Family Polymorphism

• In our case, objects can be repositories of collaborating classes

• Type system makes sure that objects from different families never mix!– Otherwise we could easily produce type errors

• Type system uses „path-dependent types“– Type name is prefixed with path to family– All fields in a path must be „final“

final HierarchyDisplay hd = new HierarchyDisplayA();final HierarchyDisplay hd2 = new HierarchyDisplayB();hd.Node n = hd.new Node(); // okhd.foo(n); // okhd2.Node n = hd.new Node(); // static errorhd2.foo(n); // static error

25

OutlineOutline

► Hierarchical RefinementsHierarchical Refinements Extending component with virtual classesExtending component with virtual classes Combining different extensionsCombining different extensions Feature-oriented decompositionFeature-oriented decomposition

► Crosscutting IntegrationCrosscutting Integration Defining wrapper classesDefining wrapper classes Observing events with pointcutsObserving events with pointcuts Variability managementVariability management


26

Feature Integration

Company

Employee

Department

0-*

ceo1 1 manager

0-*

1

workers

Display uses data and relationships of company objects

After certain changes display must be refreshed or layout recalculated

structural mapping

Design Goal:Keep components independent of each other


HierarchyDisplay


Node


CompositeNode


Connection

0-*connections

parent

child

0-*

children

behavioral mapping

27CompanyHierarchyDisplay

CompanyHierarchyBinding

Node

CompositeNode

CompanyNode

DepartmentNode

WorkerNode

HierarchyDisplay

Node

CompositeNode

Connection

0-*connections

parent

child 0-*

children

Feature Integration

Company

Employee

Department

0-*

ceo1 1 manager

0-*

1

workers

Collaboration Interface

Binding toCompany Model

Concrete Component

VisualizationConcern

getRoot()calculateLayout()draw()setView()refresh()

IHierarchyDisplay

getText()textFits()textChanged()

Node

getChildAt()getChildCount()childrenChanged()

CompositeNode

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Feature Integration - BindingsAdapting company model objects to visual nodes

refresh()...


textChanged()...

Node

childrenChanged()...

CompositeNode


DepartmentNode


CompanyNode

getText()

WorkerNode

Company

Employee

Department

0-*

ceo

1

1 manager

0-*

1

wraps

wraps

wraps

cclass WorkerNode extends Node wraps Employee { String getText() { return wrappee.getFullName(); } }

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Wrapper Recycling

cclass CompanyHierarchyBinding { cclass WorkerNode extends Node wraps Employee { ... } ... }

void test() { CompanyHierarchyBinding hier = new CompanyHierarchyDisplay();

Employee anna = new Employee();

assert(hier.WorkerNode(anna) == hier.WorkerNode(anna));

Employee peter = new Employee();

assert(hier.WorkerNode(anna) != hier.WorkerNode(peter)); }

wrapper is created on demand

wrapper is reused for the same object

wrapper is destroyed by garbage collector

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refresh()...


textChanged()...

Node

childrenChanged()...

CompositeNode


DepartmentNode


CompanyNode

getText()

WorkerNode

Company

Employee

Department

0-*

ceo

1

1 manager

0-*

1

wraps

wraps

wraps

Feature Integration - Pointcuts

After certain changes display must be updated

Call after children changed

Call after text change

Call when redraw is needed

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Changes in Company Model

getCEO()getDepartmentAt()getDepartmentCount()setCEO()addDepartment()removeDepartment()transferTo()

Company

getDepartment()getFullName()getInitials()getRole()getSex()setName()setFirstName()setLastName()setRole()setDepartment()

Employee

getName()getManager()getWorkerAt()getWorkerCount()setName()setManager()addWorker()removeWorker()

Department

0-*

ceo11

manager

0-*

1workers

Affects text of a node

Affects children of a node

No direct effect

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Observing Changes in Company Model

pointcut departmChildrenChange() : execution( Department.addWorker(..)) || execution( Department.removeWorker(..));

pointcut companyChildrenChange() : execution( Company.addDepartment(..)) || execution( Company.removeDepartment(..));

pointcut displayChange() : execution( company..setName(..)) || departmChildrenChange() || companyChildrenChange();

after(Department d) : departmChildrenChange() && this(d) { DepartmentNode(d).calculateLayout();}

after(Company c) : companyChildrenChange() && this(c) { CompanyNode(c).calculateLayout();}

after() : displayChange() && !cflowbelow(displayChange()) { refresh(); }

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Support for Variability

• Several dimensions of variations– Two dimensions in our example:

•HierarchyDisplay implementation variations• Data model variations

• All defined to a common interface– Implement different facets of the interface– All parameterized over other facets

• Collaboration interface abstraction makes them composable

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Combining Variations

IHierarchyDisplay

HierarchyDisplay

Angular-HierarchyDisplay


Collaboration Interface Component Bindings

Component Implementations Components


Adjusted-CompanyHierarchyDisplay

Angular-CompanyHierarchyDisplay

AdjustedAngular-CompanyHierarchyDisplay

GUIHierarchyBinding

Adjusted-HierarchyDisplay

AdjustedAngular-HierarchyDisplay

GUIHierarchyDisplay

Adjusted-GUIHierarchyDisplay

Angular-GUIHierarchyDisplay

AdjustedAngular-GUIHierarchyDisplay

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CaesarJ Aspects are Objects

• Aspects can be instantiated and referenced as any other object

• References to aspects can be polymorphic– aspectual polymorphism

• Multiple instances of an aspect can be created and used simultaneously

• Aspects can contain state– To parameterize their behavior– To accumulate results of observation

• Aspects can be deployed on different scopes

36

CaesarJ Aspects are Objects

• Aspects in CaesarJ are classes that have pointcuts and advice

• Keyword deployed creates and activates a singleton instance of the class

public deployed cclass CompanyChangeTracer {

pointcut change() : execution(void company.*.set*(..)) || execution(void company.*.add*(..)) || execution(void company.*.remove*(..)) || execution(void Company.transferTo(..));

after(Object o): change() && this(o) { System.out.println( "Object '" + o.toString() + "' changed"); }}

37

Dynamic Aspect Deployment

CompanyChangeTracer asp1 = new CompanyChangeTracer();

CompanyChangeTracer asp2 = new CompanyChangeTracer();

dept.setName(“DeptA”); /* not intercepted */

deploy asp1;dept.setName(“DeptB”); /* intercepted by asp1 */

deploy asp2;dept.setName(“DeptC”); /* intercepted by asp1 and asp2 */

undeploy asp1;undeploy asp2;dept.setName(“DeptD”); /* not intercepted */

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Aspect Scoping

Thread local deployment:

Object local deployment:

CompanyChangeTracer asp1 = new CompanyChangeTracer();deploy(asp1) { new deptm.setName(“DeptA”); }

CompanyChangeTracer asp1 = new CompanyChangeTracer();CompanyChangeTracer asp1 = new CompanyChangeTracer();Department dept1 = new Department(“deptA”);Department dept2 = new Department(“deptB”);DeploySupport.deployOnObject(asp1, dept1);DeploySupport.deployOnObject(asp2, dept2);dept1.setName(“deptC”); /* intercepted by asp1 */dept2.setName(“deptD”); /* intercepted by asp2 */dept3.setName(“deptF”); /* not intercepted */DeploySupport.undeployFromObject(asp1, dept1);DeploySupport.undeployFromObject(asp2, dept2);

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Integrating Distributed Components

method calls

rmi://server.net/Company

host.deployAspect(h)

advice calls

HierarchyDisplay

IHierarchyDisplay



ClientServer

Company

Employee

Department

0-*

ceo

1

1 manager

0-*

1

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Remote Aspect Deployment

CaesarHost host = new CaesarHost(“rmi://localhost/”);host.activateAspectDeployment();

Server side:

• Use execution pointcut, because calls can cross process boundaries

• Pointcut cflow cannot cross thread boundaries• Prepare aspect classes with Caesar RMI compiler

CaesarHost host = new CaesarHost(“rmi://localhost/”);ICompanyHierarchyDisplay hier = new CompanyHierarchyDisplay();host.deployAspect(hier);...host.undeployAspect(hier);

Client side:

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Deployment on a Distributed Flow

deployed public cclass CompanyDisplayLogging { void around(): execution(draw(..)) && this(CompanyHierarchyDisplay) { CompanyLogger logger = new CompanyLogger(); deploy (logger) { proceed(); } }}

deployed public cclass CompanyDisplayLogging { void around() : execution(draw(..)) && this(CompanyHierarchyDisplay) { CompanyLogger logger = new CompanyLogger(); RemoteDeployment.deployOnControlFlow(logger); proceed(); RemoteDeployment.undeployFromControlFlow(logger); }}

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OutlineOutline► Hierarchical RefinementsHierarchical Refinements

Extending component with virtual classesExtending component with virtual classes Combining different extensionsCombining different extensions Feature-oriented decompositionFeature-oriented decomposition

► Crosscutting IntegrationCrosscutting Integration

Defining wrapper classesDefining wrapper classes Observing events with pointcutsObserving events with pointcuts Variability managementVariability management


43

CaesarJ Development Tools

• CaesarJ IDE is available as a Eclipse plug-in– Integrated compiler and editor– Specialized visualization – Debugging support

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More on CaesarJ

• Visit http://caesarj.org for more information– Download plug-in and examples– Read documentation and tutorial– Subscribe to mailing list

• Case studies– An interpreter of an experimental OO language– A real-time computer game– Access Control Service (by KU-Leuven, Belgium)– Mobile order management system (running)

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References• E. Ernst, K. Ostermann and W. Cook. A Virtual Class Calculus. ACM Symposium on Principles of

Programming Languages (POPL'06), ACM SIGPLAN-SIGACT, 2006.• I. Aracic, V. Gasiunas, M. Mezini and K.Ostermann. Overview of CaesarJ. Transactions on Aspect-

Oriented Software Development I. LNCS, Vol. 3880, pp. 135 - 173, Feb 2006.• M. Mezini and K. Ostermann. Variability Management with Feature-Oriented Programming and Aspects.

Foundations of Software Engineering (FSE-12), ACM SIGSOFT, 2004. • M. Mezini and K.Ostermann. Conquering Aspects with Caesar.

In (M. Aksit ed.) Proceedings of the 2nd International Conference on Aspect-Oriented Software Development (AOSD)2003, ACM Press, pp. 90-100.

• M. Mezini and K. Ostermann. Integrating Independent Components with On-Demand Remodularisation. 17th ACM Conference on Object-Oriented Programming, Systems, Languages, and Applications (OOSPLA), 2002, Sigplan Notices, 37 (11), pp. 52 - 67.

• M. Mezini, L. Seiter, K. Lieberherr. Component Integration with Plug-and-Play Adapters. In M. Aksit (ed.) "Software Architectures and Component Technology: The State of the Art in Software Development", Kluwer Academic Publishers

• S´. Herrmann and M. Mezini. LAC: Aspectual Components in Lua. Workshop on Advanced Separation of Concerns, International Conference on Software-Engineering 2001 (ICSE '01)

• S. Herrmann and M. Mezini. Connectors for bridging mismatches between the components of a software engineering environment. IEE Proceedings - Software Engineering Special Issue: Aspect-oriented and component-based Software Development

• S. Herrmann and M. Mezini. Pirol: A Case-Study for Multi-Dimensional Separation of Concerns in Software-Engineering Environments. ACM Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA '00), Sigplan Notices, Vol. 35, No. 10

• L. Seiter, M. Mezini and K. Lieberherr. Dynamic Component Gluing. Proceedings of the 1st International Conference on Generative and Component-Based Software Engineering (GCSE '99)}, LNCS 1477

• M. Mezini and K. Lieberherr. Adaptive Plug-and-Play Components for Evolutionary Software Development. ACM 13th Annual Conference on Object-Oriented Programming, Systems, Languages and Applications (OOPSLA '98), Vancouver, Sigplan Notices, Vol. 33, No. 10., pp. 97-116.

• K. Lieberherr D. Lorenz, M. Mezini. Programming with Aspectual Components. Tech. Report. College of Computer Science, Northeastern University

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People

• Project Leads– Prof. Mira Mezini – Prof. Klaus Ostermann

• Developers– Ivica Aracic – Vaidas Gasiunas – Karl Klose – Thiago Tonelli Bartolomei – Christian Meffert – Jochen Ungers – Daniel Zwicker – Andreas Wittmann – Walter A. Werner – Jürgen Hallpap

Klaus Osterman

n

Vaidas GasiunasIvica Aracic

Mira Mezini

47

http://caesarj.org

Thank you!

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