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Aspect Oriented Programming - syntax
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L'implementazione dell'AOP che ho realizzato è semplice, ma sufficiente per un primo approccio all'AOP.
Gli elementi base che ho implementato sono essenzialmente tre:
- aspect
- pointcut
- advice and introduction
Un aspect è definito con la seguente sintassi:
aspect nameOfTheAspect {
....
#aspect definition: pointcuts, advices, introductions..
....
} pointcut pt_name -class classname_spec pointcut pt_name -call methodname_spec pointcut pt_name -trace membername_spec pointcut AllFile -class {File* *File}
#we can use the wildcard characters '*' and '?'
Un' introduction semplicemente permette di specificare le modifiche da apportare alle classi intercettate
da uno o più pointcut.
introduction name -parent pointcutNameList newParents
introduction name -interface pointcutNameList newInterfaces
introduction name -code pointcutNameList newCode- -parent: aggiungere classi da cui derivano le classi intercettate
- -interface: aggiungere delle interfacce alle classi intercettate
- -code: aggiungere del codice (tipicamente nuovi metodi) alle classi intercettate.
Per esempio, utilizzando il pointcut AllFile dichiarato nell'esempio precedente, posso scrivere:
introduction addGetFileLength -code {AllFile} {
proc getFileLength {filename} {
return [file $filename size ]
}
}
Seguendo lo stesso principio è possibile scrivere un pointcut di tipo -call
pointcut AllOpenFileMethods -call {File* open* *File open*}
#we can use the wildcard characters '*' and '?'
Sarà quindi possibile usando questo pointcut scrivere un advice per modificare il codice dei metodi intercettati come per esempio:
advice -after { AllOpenFileMethods } {
puts "the file is opened"
}
# this simple implementation of AOP consist in a namespace Aspect and a global
# procedure "aspect".
# Within it you can declare some "pointcut" and "advice"
#
# 1) All the aspect(s) declaration(s) must be at the start of the source code,
# before any class declaration
# 2) pointcut must be defined as a couple of names of type
# "<class> <proc/method>" Note that <class> and <proc/method>
# name can contains glob char "*?" to match more than one name
# 3) advice will be declared after all the pointcuts declaration
# in the advice body, if the string "functionName" is presents, then a
# variable functionName containing the name of the current function will be set
# example:
# aspect nameOfAspect {
# pointcut AA -call <classname procname>
# pointcut AA -call <classname2 procname2 classname3 procname3 ... >
# pointcut BB -call <&...same as above...>
# advice -after AA ?BB? {
# <lines of code to be executed>
# ....
# }
# advice -before AA ?? {
# <lines of code...>
# }
# }
# Syntax:
# pointcut <pt_name> -class <classname_spec>
# introduction <name> -parent <pointcutNameList> <newParents>
# introduction <name> -interface <pointcutNameList> <newInterfaces>
# introduction <name> -code <pointcutNameList> <newCode>
# introduction <name> -name <pointcutNameList> <newClassName>
# (create a new class definition that can be used in following advice )
#
# pointcut <pt_name> -call <methodname_spec>
# advice <name> -around <pointcutNameList> <code>
# advice <name> -before <pointcutNameList> <code>
# advice <name> -after <pointcutNameList> <code>
# advice <name> -cflow <pointcutNameList> <code> --- Not Yet Implemented
#
# pointcut <pt-name> -trace <membername_spec> --- Not Yet Implemented
# evaluate <name> -set <pointcutNameList.> --- Not Yet Implemented
# evaluate <name> -get <pointcutNameList> --- Not Yet Implemented
# evaluate <name> -both <pointcutNameList> --- Not Yet Implemented
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Copyright © 2002, by eriskouma.com. All rights reserved. last modified on: Sat, 09 November 2002
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