AspectJ%20Syntax%20Basics

1
AspectJ Syntax Basics
2
Identify Join Points

• 1 public class Bit
• 2 bool value
• 3 void Set()
• 4 value true
• 5
• 6 void Clear()
• 7 value false
• 8

9 void Toggle 10 if(Get()) Set() 11
else clear() 12 13 void Get() 14
return value 15 16
3
Pointcuts

• Named
• pointcut AllCall() call( (..))
• Anonymous
• before() call( (..))

4
Named Pointcut Syntax

• access specifier pointcut pointcut-
• name(args) pointcut definition

5
Why Named Pointcuts?

• Pointcut Reuse
• Separation of two specifications
• Where additional behavior is to be applied?
• What is the additional behavior?
• Late Binding of Design Decisions

6
Pointcut Reuse Separation

• public pointcut StringArg(String s)
• execution( (..)) args(s)
• around(String s) StringArg(s)
• / Omit execution if null argument /
  
• around(String s) StringArg(s)
• / Omit execution if not valid XML
  /

7
Late Binding

• abstract aspect Lock
• pointcut CriticalSections()
• before() CriticalSections()
• / Acquire lock /
• after() CriticalSections()
• / Release lock /

8
Late Binding

• aspect BufferLock extends Lock
• pointcut CriticalSections()
• call( Buffer.Write(..))

9
Poincut composition

• pointcut1 pointcut2
• pointcut1 pointcut2
• ! pointcut

10
Signatures

• Type Signatures
• Method Signatures
• Field Signatures

11
Example Type Signature

• javax..Model

Any sub-type of a given type
Any number of characters including period
Any number of characters excluding the period
12
Exercise 1

• Write down the type signature to pick out only
  the sub-types of all the types in the javax
  package or its direct and indirect subpackages
  that have a name ending in Model.

13
Example Method Signature

• javax...addListener(EventListener)

14
Example Field Signature

• !public static banking...

15
Cflow and Cflowbelow

• Cflow (Pointcut) - Captures all join points in
  the control flow of the join points matched by
  the specified pointcut, including the join points
  themselves.
• Cflowbelow(Pointcut) Excludes the matching join
  points, matches everything below.

16
cflow( execution Account.debit(..))

• 1 void debit(int amount)
• 2 if( this.getBalance() gt amount)
• 3 this.setBalance( this.getBalance()
  amount)
• 4
• 5 int getBalance()
• 6 return db.Query(name, balance)
• 7
• 8 int setBalance(int balance)
• 9 db.Update(name, balance, balance)
• 10

17
Lexical Pointcuts

• within( type pattern )
• withincode( method or constructor pattern)

18
Identify matches within(Bit)

• 1 public class Bit
• 2 bool value
• 3 void Set()
• 4 value true
• 5
• 6 void Clear()
• 7 value false
• 8

9 void Toggle 10 if(Get()) Set() 11
else clear() 12 13 void Get() 14
return value 15 16
19
withincode( Bit.et(..))

• 1 public class Bit
• 2 bool value
• 3 void Set()
• 4 value true
• 5
• 6 void Clear()
• 7 value false
• 8

9 void Toggle 10 if(Get()) Set() 11
else clear() 12 13 bool Get() 14
return value 15 16