AspectJ Syntax Basics

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 }

Pointcuts Named pointcut AllCall(): call( * *(..)); Anonymous before(): call( * *(..)) { … }

Named Pointcut Syntax [access specifier] pointcut pointcut- name([args]): pointcut definition

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

Pointcut Reuse & Separation public pointcut StringArg(String s): execution( * *(..)) && args(s); around(String s): StringArg(s) { /* Omit execution if null argument */ } /* Omit execution if not valid XML */ }

Late Binding abstract aspect Lock { pointcut CriticalSections(); before(): CriticalSections() { /* Acquire lock */ } after(): CriticalSections() { /* Release lock */

Late Binding … aspect BufferLock extends Lock { pointcut CriticalSections(): call(* * Buffer.Write(..)); }

Poincut composition pointcut1 && pointcut2 pointcut1 || pointcut2

Signatures Type Signatures Method Signatures Field Signatures

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

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.

Example Method Signature * javax..*.add*Listener(EventListener+)

Example Field Signature !public static * banking..*.*

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.

cflow( execution Account.debit(..)) 1 void debit(int amount) { 2 if( this.getBalance() > 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 }

Lexical Pointcuts within( type pattern ) withincode( method or constructor pattern)

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 }

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 }