Question

Is there a way I can tell Java to trace certain functions by marking them with an annotation? I want to be able to do this:

class Foo {

    @trace
    int foo(int bar) {
        return bar + 5;
    }
}

Then, if tracing is enabled, I get:

** Entering foo(5)

** foo returning: 10

Answer 1

you can do this using spring aop, with @Around annotations

How to implement AOP logging:

add this to applicationContext.xml

 <aop:aspectj-autoproxy/>
  <context:annotation-config/>
  <context:component-scan base-package="com.company.*"/>

create the following class in com.company.* package:

package com.company.*;

import org.apache.log4j.Logger;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Component;
import org.springframework.util.StopWatch;

@Component
@Aspect
public class AOPMethodLogger {

    @Around("bean(*Service)")
    public Object timeMethod(ProceedingJoinPoint joinPoint) throws Throwable {
        StopWatch stopWatch = new StopWatch();
        stopWatch.start();
        Object retVal = joinPoint.proceed();
        stopWatch.stop();
        if(stopWatch.getTotalTimeMillis() > 35){
            StringBuffer logMessageStringBuffer = new StringBuffer();
            logMessageStringBuffer.append(joinPoint.getTarget().getClass().getName());
            logMessageStringBuffer.append(".");
            logMessageStringBuffer.append(joinPoint.getSignature().getName());
            logMessageStringBuffer.append("(");
            logMessageStringBuffer.append(joinPoint.getArgs());
            logMessageStringBuffer.append(")");
            logMessageStringBuffer.append(" execution time: ");
            logMessageStringBuffer.append(stopWatch.getTotalTimeMillis());
            logMessageStringBuffer.append(" ms");
            System.out.println(logMessageStringBuffer.toString());
        }
        return retVal;
    }

}