Using AOP to Ease Evolution

Presented by David Shepherd (QLI & UD)

Co-Authors: Thomas Roper (QLI) and Lori Pollock (UD)

2

Making a Distributed Database Application

Issue: Stale Data

DB

DB

DB

Delaware

Hawaii

North CarolinaReq

uest

Data

Request Data

Data

Data

Detective

DMV

Update

?notify

Motivation for Evolution in the Field

Databases with

Records Of Cars

Detective App.Non-Trivial Data Mining

Clerk App.Update car data

3

Desired Evolution Task

Notification Scheme

DMV App DB Server

DetectApp

Interesting Update

Return Results Send Primary Keys

Return Results

Query DB

Can a database support this functionality?

Who is interested in

these records?

No

4

Software Evolution Problem

Open Source Software X

AdditionalFeature(s)

Have

Open-Source Software (OSS) App

Need to Modify Application

Adding Feature(s)

Issues

OSS evolves independently

Injection of feature

Maintenance of feature

Potential Solutions

OOP vs. Aspect-Oriented Programming (AOP)

5

Overview of Evolution Process

Original Open

Source Software

Augmented Open

Source Software

Original Open

Source Software

Feature

Augmented New Version

OSS

NewVersion

OSS

Feature

Aug-mented

New VersionOSS2

NewVersionOSS2

Feature

OOP Process

AOP Process

1

1

2

2

New Version of OSS Available

6

Possible OOP Solution

DBObserverexecutes

notifies Notifies

listeners

Add Code into method Add Code into method Add methods

Add interface Add implementation of interface

try{ // Evaluate the sql query Table result = sql_executor. execute(db_conn, query); query.notifyObservers(result); error = false; return t;}

public class SQLQuery implements Subject{ ... public void notifyObservers(Table result){ //Get the primary keys, table, etc. ResultInfo resultInfo =... //Get query info from the query QueryInfo queryInfo =... //update all ... } public SQLQuery(){ addObserver(DatabaseDistributedNotifier. getInstance()); ... }

SQLQuery

notifyObservers

getQuery

addObserver

SQLQuery

addVar

Clear …

DbServerexecuteQuery

openConnection

parseQuery

commitQuery

Public interface DBObserver{……}

Public class MckoiDBObserver implements DBObserver {……}

Original OSS CodeOriginal OSS Code New Feature Code

7

2 packages

3 classes

*needs to be added here

Crosscutting Concern (CCC)

An Outcome of OOP Solution

This represents one .java fileTaller = Longer file

Blue lines representour feature’s implementation

8

Another Outcome of OOP Solution

Tangling

Statement level

Method level

9

Pointcut

Pointcut

AOP Solution

ObserverProtocolSQLQueryexecute

Prepare

SQLQuery

Pointcut SubjectChange

Pointcut updateObserver

Pointcut registration

DBObserverProtocol

Pointcut subjectChange

Pointcut updateObserver

Pointcut registration

Declare Subject

Declare Observer

DBObserver

update

Feature Implementation

Original CodeBase

Key Feature:

Only loosely coupled with Original OSS

Key Feature 2:

Observer concern

modularized

Pointcut

10

Finding Code Insertion Points

Database Codebase

A First Step in implementation (for both methods)

11

Finding Insertion Point – A Closer Look

Statement “Select”’s evaluate method /** * Evaluates the select statement with the given Database context. */ public Table evaluate() throws DatabaseException {

DatabaseQueryContext context = new DatabaseQueryContext(database);

// Check the permissions for this user to select from the tables in the // given plan. checkUserSelectPermissions(context, user, plan);

boolean error = true; try {

Table t = plan.evaluate(context); error = false; return t; }

Snippet from JDBCDatabaseInterface’s execQuery method . . .… try {

// Evaluate the sql query.

Table result = sql_executor.execute(database_connection, query);

// Put the result in the result cache... This will lock this object // until it is removed from the result set cache. Returns an id that // uniquely identifies this result set in future communication. // NOTE: This locks the roots of the table so that its contents // may not be altered. result_set_info = new ResultSetInfo(query, result); result_id = addResultSet(result_set_info);

}…

Which place is better?

12

OOP Process – Find Insertion Point

1Insert in most likely place2 Test – Fail3 Remove Code

We removed an extra statement

Causing two errors

4Continue Cutting and Pasting . . .

5Answer Co-Worker’s

Question About Another Project

Ponder, where was I?(what is my working set)

13

AOP Process – Find Insertion Point

1Set Pointcut to Most Likely Place2 Test – Fail3 Change Pointcut4

Continue Changing Pointcut . . .

5Answer Co-Worker’s

Question About Another Project

Only working with one file: Easy to remember working set

14

New OSS Version Available

Original Open

Source Software

Augmented Open

Source Software

Original Open

Source Software

Feature

Augmented New Version

OSS

NewVersion

OSS

Feature

Aug-mented

New VersionOSS2

NewVersionOSS2

Feature

OOP Process

AOP Process

2

2

15

OOP Solution another outcome

Database Codebase

Process with OOP1. Find Feature Code

2. Extract Feature Code

3. Find new insertion points

4. Insert Feature code

New Database Codebase

16

Evolution of Codebase: AOP Solution

Database Codebase

New Code Well-Modularized Separate from main code base

Refers to main code base

New Database Codebase

AOP: At worst, realign pointcut

references

17

Concluding Remarks - Lessons Learned

AOP saves effort when adapting an open-source project

Eases Initial Maintenance Task - Add New Feature Non-Invasive Change

Maintaining Working Set

Eases Evolution - Adapt to OSS Change Finding the Feature

Only Re-Align Pointcuts

Status Working Implementation

Continue to use in ongoing industry research

AOP is AOK!

18

19

Slide graveyard

20

AOP Process – Find Insertion Point

Snippet from JDBCDatabaseInterface’s execQuery method . . .… try {

// Evaluate the sql query. Table result = sql_executor.execute(database_connection, query); query.notification(result); error=false; // Put the result in the result cache... This will lock this object // until it is removed from the result set cache. Returns an id that // uniquely identifies this result set in future communication. // NOTE: This locks the roots of the table so that its contents // may not be altered. result_set_info = new ResultSetInfo(query, result); result_id = addResultSet(result_set_info);

}…

21

22

com.m

ckoicom.m

ckoi.database

com.m

ckoi.database.control

com.m

ckoi.toolscom.m

ckoi.util

com.m

ckoi.store

com.m

ckoi.runtime

com.m

ckoi.jfccontrols

com.m

ckoi.debug

com.m

ckoi.database.sql

com.m

ckoi.database.regexbridge

com.m

ckoi.database.procedure

com.m

ckoi.database.jdbcserver

com.m

ckoi.database.jdbc

com.m

ckoi.database.interpret

com.m

ckoi.database.global

com.mckoi

com.mckoi.database

com.mckoi.database.control

com.mckoi.database.global

com.mckoi.database.interpret

com.mckoi.database.jdbc

com.mckoi.database.jdbcserver

com.mckoi.database.procedure

com.mckoi.database.regexbridge

com.mckoi.database.sql

com.mckoi.debugc

om.mckoi.jfccontrols

com.mckoi.runtime

com.mckoi.store

com.mckoi.tools

com.mckoi.util

23

Possible Solutions

Can a database support this functionality?

DbServer

executeQuery

openConnection

parseQuery

commitQuery

…

try{ // Evaluate the sql query Table result = sql_executor.execute(db_conn, query); query.notifyObservers(result); error = false; return t;}

public class SQLQuery implements Subject{ ... public void notifyObservers(Table result){ //Get the primary keys, table, etc. from results ResultInfo resultInfo =... //Get query info from the query QueryInfo queryInfo =... for(Iterator e = observers.iterator(); e.hasNext(); ){ ((DBObserver)e.next()). update(resultInfo,queryInfo); } } public SQLQuery(){ addObserver(DatabaseDistributedNotifier. getInstance()); ... }

SQLQuery

notifyObservers

getQuery

addObserver

removerObserver

SQLQuery

addVar

translateObjectType

clear

…

24

Quantum Leap Innovations – Business Model

What We Do We create pioneering technologies that are used by our partners to build innovative products and services.

How We Do It We support our partners as a team member by providing our unique IP, software technologies and people.

Gov’t Agencies Partners

Technology Differentiated

Products &Services

ResearchPrograms

End Users

PioneeringSoftware

Technologies

Tom, am I allowed to show this? It was from the Template.ppt in J:\Presentations.