Maven: A Developer's Notebook

Writing a Logging Aspect Using AspectJ

The first thing to do is to write the Aspect you're going to apply to the project's code which will run the Logifier plug-in. The goal here is not to do a tutorial on AspectJ (for this, see http://www.eclipse.org/aspectj/).

How do I do that?

Without further ado, here's the first part of the Aspect you'll develop:

import org.aspectj.lang.reflect.*;
import org.aspectj.lang.*;
  
public aspect Logging
{
    /**
     * All public methods that have parameters.
     */
    pointcut publicMethodsWithParameterCalls() :
        !execution(public * *())
        && execution(public * *(..));
  
    /**
     * All public static methods that have parameters.
     */
    pointcut publicStaticMethodsWithParameterCalls() :
        !execution(public static * *())
        && execution(public static * *(..));
 [...]

AspectJ extends the Java language and adds new keywords—among them aspect and pointcut. You can see here that the aspect keyword declares an Aspect (in lieu of the class keyword), and pointcut declares an identifier matching some code. AspectJ has a little language to express how to match portions of code. For example, the publicMethodsWithParameterCalls() PointCut Definition (PCD) translates to "whenever the code does not execute a public method with no parameter AND whenever the code executes a public method with parameters (signified by the .. notation, which means zero or more parameters)." Confused? In English, the previous logic-speak can be translated to: execution of all public methods that have parameters.

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