AspectJ(二)Language Introduction

AspectJ(2)Language Introduction
AspectJ(2)Language Introduction

Chapter 2. The AspectJ Language
2.1 The Anatomy of an Aspect
An Example Aspect
...snip...
Join Points and Pointcuts
After reading and study withincode demo, I begin to understand this key words. withincode, that means that be in this method of that class in this example.
PointTests.java:
package com.sillycat.easyaspectj;
import junit.framework.TestCase;
public class PointTests extends TestCase {
public static void main(String args[]) {
junit.swingui.TestRunner.run(PointTests.class);
}
public void testPointChange() {
Point sample = new Point(1, 1);
assertFalse(sample.isDirty());
sample.setX(5);
assertTrue(sample.isDirty());
sample.save();
assertFalse(sample.isDirty());
sample.setY(2);
assertFalse(sample.isDirty());
sample.save();
assertFalse(sample.isDirty());
}
}

My aspectj class AspectPoint.aj:
package com.sillycat.easyaspectj;
public aspect AspectPoint {
   private boolean Point.isDirty = false;
   public void Point.makeDirty() {
      isDirty = true;
   }
   public boolean Point.isDirty() {
      return isDirty;
   }
   public void Point.save() {
      isDirty = false;
      // add code to save point
   }
   pointcut fieldChanged(Point changed) :
   set( private double Point.*) &&
   target(changed) &&
   !withincode( Point.new(..)) &&
   withincode( void Point.setX(..)); 
   after(Point changed ) : fieldChanged(changed) {
      System.out.println("Make Dirty");
      changed.makeDirty();
   }
}

Point.java class is as follow:
public class Point {
private double x;
private double y;
private boolean isDirty = false;
Point(double x, double y) {
this.x = x;
this.y = y;
}
public void setX(double x) {
this.x = x;
isDirty = true;
}
public void setY(double y) {
this.y = y;
isDirty = true;
}
public void setPolarCoordinates(double theta, double r) {
x = r * Math.cos(theta);
y = r * Math.sin(theta);
isDirty = true;
}
...snip..

Some Example Pointcuts
When a particular method body executes: execution(void Point.setX(int))

When a method is called: call(void Point.setX(int))

When an exception handler executes: handler(ArrayOutOfBoundsException)

When the object currently executing is of type SomeType: this(SomeType)

When the target object is of type SomeType: target(SomeType)

When the executing code belongs to class MyClass: within(MyClass)

call VS. execution
Pointcut composition
Pointcut Parameters
Example: HandleLiveness

2.2. Advice
The around advice runs instead of the join point. The original action associated with the join point can be invoked through the special proceed call:
public void sayHello(String message){
System.out.println(message);
}

public static void main(String[] args) {
HelloWorld h = new HelloWorld();
h.sayHello(" study the aspectJ!");
h.sayHello(" study the spring roo!");
h.sayHello(" study the mw3!");
}
pointcut hello(HelloWorld h1, String hello):
target(h1) && args(hello) && (call (void say*(String)));

void around(HelloWorld h1,String hello): hello(h1, hello){
if(hello.indexOf("study") > 0){
System.out.print("Carl");
}
proceed(h1,hello);
}
2.3 Inter-type declarations
2.4 thisJoinPoint
System.out.print(thisJoinPoint.getSourceLocation() + ": ");
HelloWorld.java:11: Carl study the aspectJ!

references:
http://www.eclipse.org/aspectj/doc/released/progguide/language.html
http://sishuok.com/forum/posts/list/281.html