AspectJ aspect is not applied in LTW scenario

问题

I am trying to use AspectJ in a standalone application but does not seem to work.

Here are the classes I created-

package oata.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class AspectJTest {


    @Around("execution(* *..*(..))")
    public void around(ProceedingJoinPoint jp) throws Throwable {
        System.out.println("around fired");
        jp.proceed();
    }
}

package oata;

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

@Target(value = ElementType.METHOD)
@Retention(RetentionPolicy.SOURCE)
public @interface AspectTest {
}

package oata;

import oata.AspectTest;

public class TestAspect {
    public void doItWithout(int i) {
        double s = Math.acos(i);
    }

    @AspectTest
    public void doItAnnotated(int i) {
        double s = Math.acos(i);
    }

    public void doItAspect(int i) {
        double s = Math.acos(i);

    }
}

package oata;

import java.util.Date;

public class Test {
    public Test() {
    }

    public static void main(String arg[]) {
        // performance testing
        // invoke method without aspect
        long t1 = new Date().getTime();
        for (int i = 0; i < 1; i++) {
            new TestAspect().doItWithout(i);
        }
        System.out.println("Invoke without aspect:"
                + (new Date().getTime() - t1));
        // invoke method with annotated aspect
        t1 = new Date().getTime();
        for (int i = 0; i < 1; i++) {
            new TestAspect().doItAnnotated(i);
        }
        System.out.println("Invoke annotated aspect method:"
                + (new Date().getTime() - t1));
        // invoke method with aspect but not annotated
        t1 = new Date().getTime();
        for (int i = 0; i < 1; i++) {
            new TestAspect().doItAspect(i);
        }
        System.out.println("Invoke aspect method:"
                + (new Date().getTime() - t1));
    }
}

Also under src/META_INF folder I have created aop.xml file

<aspectj>
    <aspects>
        <aspect name="oata.aspect.AspectJTest" />
    </aspects>
    <weaver>
        <include within="oata.*" />
    </weaver>
</aspectj>

Then from the command line when I try running the Test.java using the below command the System.out.println in the advice does not get printed-

\TestAspectJ\bin>java -javaagent:D:\Project\workspaces\RCS_3.2.1\TestAspectJ\src\aspectjweaver-1.6.10.jar oata.Test

Can anyone please let me know what is it that I am doing wrong.

Thanks AA

回答1:

Few things:

Is your META-INF/* folder definitely being copied to your bin folder where you are running the app from?
You are specifying an include of oata.*, that will only include direct classes in the oata package, if you want further sub packages (and I think you do) you need oata..*
Have you tried specifying weaver options="-verbose" - does that show you anything? If it shows you nothing the aop.xml file is not being found. If it does show you something it will tell you which aspects are being turned on. Perhaps then augment it with -debug to see more about what is going on.
I might include a !within(AspectJTest) complaint to your pointcut or you could end up self advising and failing with a stack overflow when it does start working.
Finally, I know you aren't using it now but if you intend to use that annotation for matching with AspectJ you will need to change it from SOURCE retention because AspectJ works at the byte code level and won't see if it has source retention.

回答2:

Andy is right with everything he said. Because you seem to be a beginner in AspectJ as well as Java, I have refactored your sample code a bit in order to help you get started. Things I noticed along the way:

You use a very old AspectJ version 1.6.10. It is from 2010 and not even the latest 1.6 version (which would be 1.6.12). How about using the current AspectJ version 1.8.6?
I am a clean code guy and noticed that your class names are rather obfuscating what you want to demonstrate with the sample code. So I renamed them:
- Test → Application
- TestAspect → Helper
- AspectTest → MyAnnotation
- AspectJTest → MethodInterceptor
I also changed the Helper methods' return types so as to return something other than void in order to demonstrate the next issue.
Your @Around advice has a return type of void. This way it does not work if the pointcut hits a non-void method. I changed the return type to Object and the code to return the result of proceed() in order to show how this can be done in a more generic way.
Your @Around advice always logs the same message. I updated it to log the actual joinpoint info (before and after the proceed() call) so we can see what is happening on the console log.
As Andy said, obviously you plan to use the annotation in order to match annotated methods with a pointcut. Thus, I changed the retention scope to RUNTIME.
Your pointcut targets all method executions including Application.main and Helper.doItWithout. I changed the pointcut to only target methods either bearing @MyAnnotation or with a substring "Aspect" in their method name.
You seem to wish to profile method execution times and compare methods with aspects applied to methods not targeted by aspects. Instead of creating lots of Date instances and calling new Date().getTime() (returns milliseconds) you can just use System.nanoTime() (returns nanoseconds).
When profiling, you want to measure method execution time, not object creation time. Thus, I changed the code to just create one Helper instance which is then reused throughout the main method.
The Application class does not need an empty default constructor because it will be generated automatically by the JVM.
In order to get meaningful profiling results you should use a bigger number of repetitions (such as a million). I introduced a constant named LOOP_COUNT in order to simplify this for all three loops.
Attention! If you want to measure method execution times you should not print anything in your aspect because then you would also be measuring the time it takes to write something to the console. Thus, I have commented out the printing statements in the aspect. You can still activate them for smaller numbers of repetitions in order to see what is going on.

Refactored code:

package oata;

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

@Target(value = ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface MyAnnotation {}

package oata;

import oata.MyAnnotation;

public class Helper {
    public double doItWithout(int i) {
        return Math.acos(i);
    }

    @MyAnnotation
    public double doItAnnotated(int i) {
        return Math.acos(i);
    }

    public double doItAspect(int i) {
        return Math.acos(i);
    }
}

package oata;

public class Application {
    private static final int LOOP_COUNT = 100000000;

    public static void main(String arg[]) {
        Helper helper = new Helper();
        System.out.printf(
            "Profiling statistics for %,d repetitions%n%n",
            LOOP_COUNT
        );

        long startTime = System.nanoTime();
        for (int i = 0; i < LOOP_COUNT; i++)
            helper.doItWithout(i);
        System.out.printf(
            "Method not targeted by aspect:%n    %,15d ns%n",
            System.nanoTime() - startTime
        );

        startTime = System.nanoTime();
        for (int i = 0; i < LOOP_COUNT; i++)
            helper.doItAnnotated(i);
        System.out.printf(
            "Method targeted by aspect because it is annotated:%n    %,15d ns%n",
            System.nanoTime() - startTime
        );

        startTime = System.nanoTime();
        for (int i = 0; i < LOOP_COUNT; i++)
            helper.doItAspect(i);
        System.out.printf(
            "Method targeted by aspect because of its name:%n    %,15d ns%n",
            System.nanoTime() - startTime
        );
    }
}

package oata.aspect;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;

@Aspect
public class MethodInterceptor {
    @Around("execution(@oata.MyAnnotation * *(..)) || execution(* *Aspect*(..))")
    public Object around(ProceedingJoinPoint jp) throws Throwable {
//      System.out.println("BEFORE " + jp);
        Object result = jp.proceed();
//      System.out.println("AFTER  " + jp);
        return result;
    }
}

Sample console log for 1 repetition with aspect log statements enabled:

Profiling statistics for 1 repetitions

Method not targeted by aspect:
            153.893 ns
BEFORE execution(double oata.Helper.doItAnnotated(int))
AFTER  execution(double oata.Helper.doItAnnotated(int))
Method targeted by aspect because it is annotated:
          3.102.128 ns
BEFORE execution(double oata.Helper.doItAspect(int))
AFTER  execution(double oata.Helper.doItAspect(int))
Method targeted by aspect because of its name:
             55.295 ns

As you can see here, the results are not very conclusive with just one call per method.

Sample console log for 100,000,000 (a hundred million) repetitions with aspect log statements disabled:

Profiling statistics for 100.000.000 repetitions

Method not targeted by aspect:
        843.407.034 ns
Method targeted by aspect because it is annotated:
      1.219.571.173 ns
Method targeted by aspect because of its name:
      1.175.436.574 ns

Now the result is more conclusive: The method not targeted by any aspect is executed more quickly than the next two methods which have about equal execution time of 1.2 seconds, which was to be expected because the pointcuts used can be determined statically during compilation time (for CTW) or weaving time (for LTW).

来源：https://stackoverflow.com/questions/32157798/aspectj-aspect-is-not-applied-in-ltw-scenario

标签

java

aspectj

load-time-weaving