AspectJ Cheat Sheet

A Programming › Java cheat sheet in English by cs8898

AspectJ for Fortgeschrittene Java Programmierung, THI

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PRs

Terminology

Aspect	Modularization unit, compareable with Class
Introduction	introduce new method
Joinpoint	Condituion to trigger some action
Pointcut	Collection of Joinpoints
Advice	Behavior introduced at Pointcut

Weaving	Aspects get waved into the result bytecode

Aspect

public aspect LogAspect { ... }

Holds Introductions, Advices and Pointcuts

Introduction

public aspect HashableComplex {
  // introduce an interface
  declare parents: Complex implements Comparable;

  // don’t forget the class name!
  public int Complex.compareTo( Object o ) {
    ...
  }

  @Override
  public boolean Complex.equals(Object obj) {
    ...
  }
}

Can Introduce new Methods and Declarations

Advice

`before`
`after`	alternative: `after returning`, `after throwing`
`around`	use `proceed()` to execute wrapped joinpoint

Pointcut Args

target(p)	bind cut target
args(vals)	bind Pointcut arguments

pointcut setter(Point p, int newval):
target(p) &&args(newval)

Joinpoint

package hello;
public aspect WorldAspect{
  public pointcut mainOperation():
    execution (void hello.World.main(String[]));
    //execution (void*.*(*));

  before(): mainOperation() {
    println( "Hello aspect world!" );
  }

  after(): mainOperation() {
    println( "Bye aspect world!" );
  }
}

Pointcut Syntax

Wildcards
`*`	any characters, but not "."
`..`	any characters, also "."
`+`	Any Subclass / Interface
Logical	`\|\|`, `&&`, `!`

Primitive Pointcuts

`call(void Foo.m(int))`	call of a Method
`execution(Foo.(..) throws IOException)`	execution of any Method throwing an Exception
`call Foo.new(..)`	any Constructors of `Foo`
`initialization(Foo.new(int))`	initialisation by a special constructor
`handler(IOException+)`	handling of any IOException
`get(int Foo.bar)` or `set(int Foo.bar)`
`within(Foo)`	limit to foo class

* call vs execution: think of "caller" vs "executing Object"

thisJoinPoint

`getArgs(): Object[] args`
`getSignature()`
`getSourceLocation()`

thisJoinPointStaticPart equals jp.getStaticPart()
thisJoinPoint is available inside the Advice

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