Post on 16-Oct-2020
Aspect-OrientedProgramming in
Academia and Industry
Dean Wampler
Object Mentordean@objectmentor.com
1Friday, October 19, 2007
What is AOP?
History of AOP
Academia vs. industry
Future work
2Friday, October 19, 2007
class Account attr_reader :balance
def credit (amount) raise "..." unless amount >= 0 @balance += amount end
def debit (amount) raise “…” unless amount < @balance @balance -= amount endend
3Friday, October 19, 2007
Cleanand
Simple4Friday, October 19, 2007
But, Real Applications Need:
class Account attr_reader :balance def credit (amount); …; end def debit (amount); …; endend
Transactions
Persistence
Security
5Friday, October 19, 2007
Tangled
Account
Code
6Friday, October 19, 2007
Scattered
Persistence,
Code
Transactions,Security, ...
7Friday, October 19, 2007
Modularity
is
Compromised.
8Friday, October 19, 2007
We would like to say...
Before returning the Account balance, read the current balance from the persistence store.
After the Account balance changes, update the new balance in the persistence store.
Before changing the Account balance, authenticate and authorize the user.
9Friday, October 19, 2007
require ‘aquarium’class Account include Aquarium::Aspects::DSL::AspectDSL
before :attribute => :balance, :attribute_options => [:reader] do |jp, *args|
jp.context.advised_object.balance = read_from_database(…) end ...
# reopen Account
aquarium.rubyforge.org
jp: Join Point10Friday, October 19, 2007
… after_returning :attribute => :balance, :attribute_options => [:writer] do |jp, *args|
update_in_database ( jp.context.advised_object.balance,…) end ...
11Friday, October 19, 2007
… before :methods => [:credit, :debit], :attributes => [:balance] do |jp, *args|
raise “…” unless user_authorized endend
12Friday, October 19, 2007
Can’t we just use
Metaprogramming?
(when available)
13Friday, October 19, 2007
Languages that support our paradigms yield:
Higher Productivity
Higher Quality
14Friday, October 19, 2007
Refactoring AccountHandle “overdraft” requirements as an aspect
15Friday, October 19, 2007
class Account attr_reader :balance
def credit (amount) raise "..." unless amount >= 0 @balance += amount end
def debit (amount) raise “…” unless amount < @balance @balance -= amount endend
16Friday, October 19, 2007
class Account attr_reader :balance
def credit (amount) raise "..." unless amount >= 0 @balance += amount end
def debit (amount) @balance -= amount endend
17Friday, October 19, 2007
module AllowableOverdraftAccount attr_accessor :max_overdraft before :type => :Account, :method => :debit do |jp, *args| account = jp.context.advised_object if (account.balance - args[0]) < -max_overdraft raise “…” end endend
18Friday, October 19, 2007
Some HistoryA Personal Perspective
19Friday, October 19, 2007
"Open Implementation, Analysis and Design of Substrate Software"OOPSLA ’95 Tutorial
G. Kiczales, R. DeLine, A. Lee, C. Maeda
20Friday, October 19, 2007
“Black Box” Problems
Limits of Object-Oriented Modularity
Need controlled access to internals
Often at the “meta-level”
21Friday, October 19, 2007
Metaobject protocols (MOPs) and reflection
MOPs for
File system cache management
Virtual memory management tuning
Process scheduler tuning
Tutorial Reflected Work On...
22Friday, October 19, 2007
At the same time...
The Internet Bubble!!
23Friday, October 19, 2007
Persistence
Transactions
High availability
Security
...
Industry developers were feeling the pain of cross-cutting concerns (CCC)
24Friday, October 19, 2007
Common Problems Led to AspectJ
25Friday, October 19, 2007
Xerox PARC
Extension of Java
Modularizes the cross-cutting concerns (CCC)
AspectJ
26Friday, October 19, 2007
aspect AllowableOverdraftAccount { float Account.maxOverdraft; before (Account account, float amount) : execution (* Account.debit(..)) && target(account) && args(amount) { if ((account.balance - amount) < - maxOverdraft) throw new OverdraftException(...); } }}
27Friday, October 19, 2007
Most web/enterprise software is statically typed
Where the pain is felt
Why Java?
28Friday, October 19, 2007
Java’s “MOP” is insufficient for CCC
Rise of byte-code engineering tools
Configured with XML!
But sufficient as a base for AOP tools
Why Java?
29Friday, October 19, 2007
Java’s Virtual Machine (and maybe the API’s) may become more important than Java itself!
An Aside...
30Friday, October 19, 2007
Generative ProgrammingCzarnecki and Eisenacker
31Friday, October 19, 2007
Analysis and Design
Domain engineering
Feature modeling
Generative Programming
32Friday, October 19, 2007
Implementation Technologies
Generic programming
C++ template metaprogramming
AOP
Intentional programming
Generative Programming
33Friday, October 19, 2007
IBM Research
Morphed from “Subject-Oriented Programming”
Hyper/J
More ambitious than AspectJ
Multidimensional Separation of Concerns
34Friday, October 19, 2007
Symmetric AOP
Aspects as first-class citizens, like classes
Asymmetric AOP
Aspects as “adjuncts”
AspectJ’s de facto model
Multidimensional Separation of Concerns
35Friday, October 19, 2007
AOP pervasive in open-source Java enterprise frameworks
Spring
JBoss
Industry Landscape Today
36Friday, October 19, 2007
Lots of .NET/CLR AOP projects
Industry adoption still “tepid”
Industry Landscape Today
37Friday, October 19, 2007
Aspect-Oriented DesignRelearning Object-Oriented Principles
38Friday, October 19, 2007
Quantification and ObliviousnessR. Filman and D Friedman (OOPSLA 2000)
39Friday, October 19, 2007
AOP can be understood as the desire to make quantified statements about the behavior of programs, and to have these quantifications hold over programs written by oblivious programmers.
40Friday, October 19, 2007
Modules should be
open for extension,
but closed for modification
Open-Closed Principle (Meyer):
41Friday, October 19, 2007
Persistence Aspect
after set (Account.name)
Accountname
Accountfirst_namelast_name
Version 1 Version 2
???X
42Friday, October 19, 2007
Aspects make initial version easier,
but subsequent versions harder!
43Friday, October 19, 2007
AOSD-Evolution
Paradox!On the Existence of the
AOSD-Evolution Paradox. Tom Tourwé, Johan Brichau,
Kris Gybels.44Friday, October 19, 2007
Next Generation of Thought...
45Friday, October 19, 2007
Non-invasiveness vs. ObliviousnessG. Kiczales, et al.
46Friday, October 19, 2007
Modules should be aware of possible advices, without assuming specifics...
Advice: The new behavior invoked at the join point.
47Friday, October 19, 2007
… and modules should expose pointcuts...
Pointcut: The set of “interesting” join points.
… and maybe restrict access,...
48Friday, October 19, 2007
… but we should still be able to advise modules without modification.
49Friday, October 19, 2007
class Account attr_reader :balance def credit (amount) ... end def debit (amount) @balance -= amount end
STATE_CHANGE = Pointcut.new :methods => [:credit, :debit] end
aquarium.rubyforge.org
50Friday, October 19, 2007
…Aspect.new :pointcut => Account.STATE_CHANGE do | … | # Persist the change...end
51Friday, October 19, 2007
We’re rediscoveringOO Design Principles
Using Abstractions!
52Friday, October 19, 2007
Open Modules
Modular Reasoning About Advice
J. Aldrich
Cross-Cutting Programming Interfaces (XPI)
Modular Software Design with Crosscutting Interfaces
Griswold, Sullivan, et al.
For Completeness...
53Friday, October 19, 2007
What Industry Cares About
54Friday, October 19, 2007
Simple (enough) to understand and use
Strong tool support
Maintainability of long-lived software
We must get paid, ASAP!
Industry Criteria for Technology
55Friday, October 19, 2007
What Academia Cares About
56Friday, October 19, 2007
Non-trivial, interesting problems
Theoretical rigor
Publish or perish!
But longer time lines are acceptable
Academia’s Criteria
57Friday, October 19, 2007
Industry and Academia Working TogetherSome current and future growth areas for AOP
58Friday, October 19, 2007
Language-Oriented Programming
Raise the abstraction level by constructing Domain Specific Languages (DSLs)
Could hide the complexity of aspects, objects, metaprogramming, etc.
59Friday, October 19, 2007
Contrived Example:…for_types(with_pointcut(PERSISTABLE)) do |type| map_attributes_of(type) .excluding.attributes_marked(:transient) on_state_changes(:write_to_store) use_cache(:memcached)end
60Friday, October 19, 2007
What Industry Will Do...
Invent lots of little, ad hoc DSL’s
Create a “Tower of Babel” situation
Developers will struggle to learn all the DSLs of all the libraries/tools they need
61Friday, October 19, 2007
What Academia Could Do...
You understand language design, AI, etc.
Help industry understand
Globally-applicable DSL design principles
Mapping DSLs to object, aspect, … assembly code
62Friday, October 19, 2007
Massively Large Systems
How would you build a city?
How would you build a software system of the same complexity?
63Friday, October 19, 2007
What Industry Will Do...
Incremental improvements on what we already know how to do
Build systems whose complexity exceeds the capabilities of our modularity tools
Struggle to maintain these systems...
64Friday, October 19, 2007
What Academia Could Do...
Understand the unique characteristics of massive systems
Find new ways to build them in a modular, manageable way
65Friday, October 19, 2007
Don’t worry too much about industry relevance!
We need people working on longer-term problems
Instead of incremental improvements…
Focus on fundamental problems and innovation!
Some Final Thoughts
66Friday, October 19, 2007
Thank You!
dean@aspectprogramming.com
aquarium.rubyforge.org
contract4j.org
67Friday, October 19, 2007