1 / 17

AOP

AOP. Aspect-Oriented Programming. What is AOP?. Procedural Programming Abstract program into procedures. Object-Oriented Programming Abstract program into objects. Aspect-Oriented Programming Abstract program into aspects. What is Aspect?.

eman
Download Presentation

AOP

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. AOP Aspect-Oriented Programming

  2. What is AOP? • Procedural Programming Abstract program into procedures. • Object-Oriented Programming Abstract program into objects. • Aspect-Oriented Programming Abstract program into aspects.

  3. What is Aspect? • Aspects are stand-alone modules that allow the programmer to express crosscutting concerns in. • Crosscutting concerns are concerns of a program which affect (crosscut) other concerns. • A concern is any piece of interest or focus in a program. • separation of concerns (SoC) is the process of breaking a computer program into distinct features that overlap in functionality as little as possible.

  4. What is Crosscutting Concerns? void transfer(Account from, Account to, int amount) { if (!getCurrentUser().canPerform(OP_TRANSFER)) { throw new SecurityException(); } if (amount < 0) { throw new NegativeTransferException(); } Transaction tx = database.newTransaction(); try { if (from.getBalance() < amount) { throw new InsufficientFundsException(); } from.withdraw(amount); to.deposit(amount); tx.commit(); systemLog.logOperation(OP_TRANSFER, from, to, amount); } catch(Exception e) { tx.rollback(); throw e; } }

  5. What is Crosscutting Concerns? void transfer(Account from, Account to, int amount) { if (!getCurrentUser().canPerform(OP_TRANSFER)) { throw new SecurityException(); } if (amount < 0) { throw new NegativeTransferException(); } Transaction tx = database.newTransaction(); try { if (from.getBalance() < amount) { throw new InsufficientFundsException(); } from.withdraw(amount); to.deposit(amount); tx.commit(); systemLog.logOperation(OP_TRANSFER, from, to, amount); } catch(Exception e) { tx.rollback(); throw e; } }

  6. CC not properly encapsulated Logging Security … Persistence Implementation Module

  7. Abstract Concerns into Aspects Security Logging Concern Identifier Requirements Persistence

  8. AspectJ • A seamless aspect-oriented extension to the Java programming language. • The widely-used de-facto standard for AOP. • Born at Xerox Palo Alto Research Center (PARC) and later available in Eclipse Foundation open-source projects. • Java-like syntax and IDE integration. • Easy to learn and use.

  9. Join Point Model • Join Points -- Points in a running program where additional behavior can be usefully joined. • Pointcuts -- Ways to specify (or quantify) join points. A pointcut determine whether a given join point matches. • Advice -- A means of specifying code to run at a join point.

  10. A Simple Logging Example public aspect TraceAspect { private Logger _logger = Logger.getLogger("trace"); pointcut traceMethods() : execution(* *.*(..)) && !within(TraceAspect); before() : traceMethods() { Signature sig = thisJoinPointStaticPart.getSignature(); _logger.logp(Level.INFO, sig.getDeclaringType().getName(), sig.getName(), "Entering"); } }

  11. Weaving Concern Identifier Weaver Requirements

  12. Related Concept: Visitor Pattern class Wheel implements Visitable { // ... public void accept(Visitor visitor) { visitor.visit(this); } }

  13. Related Concept: Mixin class GPA include Comparable def <=>(another) # ... end end a, b = cat.gpa, dog.gpa cat.bg if cat.gpa > dog.gpa

  14. Related Concept: Policy-based Design template < typename T, template <class> class OwnershipPolicy = RefCounted, class ConversionPolicy = DisallowConversion, template <class> class CheckingPolicy = AssertCheck, template <class> class StoragePolicy = DefaultSPStorage > class SmartPtr;

  15. Example: cc98 CFF 1st # equip the spider with cache def equip(spider) orig_get_page = spider.class.instance_method :get_page dir = @dir spider.define_singleton_method :get_page do |url| filename = dir + url if File.exists? filename File.open(filename) { |file| file.read } else page = orig_get_page.bind(self).call(url) File.open(filename, "w") { |file| file.write page } page end end end

  16. Example: Rails filter before_filter :determine_locale before_filter :configure_charsets before_filter :load_personal_preferences before_filter :login_required, :except => [:index, :login] before_init_gettext :default_locale

  17. Adoption Risks • Lack of tool support, and widespread education. • Unfriendly to refactor: something as simple as renaming a function can lead to an aspect no longer being applied leading to negative side effects. • Security concern: injecting bad code. • …

More Related