AspectJ Example

How-to-install.md

Eclipse Project

Install AspectJ Development Tools

Help > Install New Software > Find the source url from http://www.eclipse.org/ajdt/downloads/ corresponding your eclipse version

AspectJ

http://www.eclipse.org/aspectj/downloads.php

Loggable.java

package cc;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface Loggable {
	String value() default "";
}

Main.java

package cc;

import org.aspectj.lang.JoinPoint;
import org.aspectj.lang.annotation.*;

@Aspect
class CpExecLogger {
	protected static int mStackIndex = 0;
	@Before("execution(* *.*(..)) && @annotation(cc.Loggable)")
	public void enter(JoinPoint pjp) throws Throwable {
		mStackIndex++;
		if (mStackIndex != 1)
			return ;
		StringBuilder cmd = new StringBuilder();
		cmd.append(String.format("%s.%s(", pjp.getSignature().getDeclaringTypeName(), pjp.getSignature().getName()));
		Object[] objs = pjp.getArgs();
		for (int i = 0; i < objs.length; i++) {
			if (i > 0)
				cmd.append(", ");
			if (objs[i] instanceof String)
				cmd.append(String.format("\"%s\"", objs[i]));
			else
				cmd.append(objs[i]);
		}
		cmd.append(String.format(");"));
		System.err.printf("[Log] %s\n", cmd);
	}

	@After("execution(* *.*(..)) && @annotation(cc.Loggable)")
	public void exit(JoinPoint pjp) throws Throwable {
		mStackIndex--;
	}
}

public class Main {
	@Loggable
	static public<T> T slave(T f) {
		System.out.println("[Slave] ... " + f);
		return f;
	}
	
	@Loggable
	static public<T> T butler(T a, T b) {
		System.out.println("[Butler] Lord, " + a + b);
		slave(a);
		slave(b);
		return a;
	}

	static public Integer hello() {
		System.out.printf("Hello\n");
		return 10;
	}
	public static void main(String[] args) {
		Integer t = slave(30);
		Integer h = butler(10, 20);
		String str = butler("a", "bstr");
	}
}

stdout.out

[Log] cc.Main.slave(30);
[Slave] ... 30
[Log] cc.Main.butler(10, 20);
[Butler] Lord, 1020
[Slave] ... 10
[Slave] ... 20
[Log] cc.Main.butler("a", "bstr");
[Butler] Lord, abstr
[Slave] ... a
[Slave] ... bstr