问题:

I would like to add "trace" messages to all my public methods as follows:

public void foo(s:String, n:int) { // log is a log4j logger or any other library   log.trace(String.format("Enter foo with s: %s, n: %d", s, n))   ...   log.trace("Exit foo")  }

Now I would like to add all those log.trace to my methods automatically with AOP (and byte code instrumentation). I am thinking about AspectJ. Does it make sense? Do you know any open-source, which does exactly that?

回答1:

I have created a simple aspect to capture the execution of public methods. The core of this AspectJ code is the pointcut definition:

pointcut publicMethodExecuted(): execution(public * *(..));

Here we are capturing all public methods with any return type, on any package and any class, with any number of parameters.

The advice execution could be visualized on code snippet below:

after(): publicMethodExecuted() {     System.out.printf("Enters on method: %s. \n", thisJoinPoint.getSignature());      Object[] arguments = thisJoinPoint.getArgs();     for (int i =0; i

This advice use thisJoinPoint to get the method signature and arguments. And that's it. Here is the aspect code:

public aspect LogAspect {  pointcut publicMethodExecuted(): execution(public * *(..));  after(): publicMethodExecuted() {     System.out.printf("Enters on method: %s. \n", thisJoinPoint.getSignature());      Object[] arguments = thisJoinPoint.getArgs();     for (int i =0; i

For more complex examples I would recommend the book AspectJ: In Action.

回答2:

@Loggable annotation and an AspectJ aspect from jcabi-aspects is a ready mechanism for you (I'm a developer):

@Loggable(Loggable.DEBUG) public String load(URL url) {   return url.openConnection().getContent(); }

To log both entry and exit, as per the question's requirements:

@Loggable(Loggable.DEBUG, prepend=true) public String load(URL url) {   return url.openConnection().getContent(); }

All logs go to SLF4J. Check this post for more details.

回答3:

You can use different pointcuts to make your requirement. This documentation will help you.

Straight forward solution

回答4:

You can try out this open source http://code.google.com/p/perfspy/. PerfSpy is a runtime logging, performance monitoring and code inspecting tool. It uses ApsectJ to weave around your application code at runtime, and logs the execution time of every method and its input parameters and values. It has a UI application, in which you can view the method invocations and their input and return values as trees. With it, you can spot performance bottlenecks and understand complex code flow.

回答5:

Here is my simple implementation to log entering , exiting and log Exceptions from methods

Annotation

package test;  import java.lang.annotation.Documented; import java.lang.annotation.ElementType; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.annotation.Target;  @Documented @Retention(RetentionPolicy.RUNTIME) @Target({ ElementType.METHOD, ElementType.TYPE }) public @interface Audit {  }

Interceptor

import java.lang.reflect.Method; import java.util.Arrays; import java.util.logging.Level; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.reflect.MethodSignature;   @Aspect public class ExceptionInterceptor {      private static final java.util.logging.Logger LOGGER = java.util.logging.Logger.getLogger(ExceptionInterceptor.class.getName());      @Around("execution(* * (..))"             + " && @annotation(test.Audit)"     )     public Object intercept(final ProceedingJoinPoint point) throws Throwable {         final Method method                 = MethodSignature.class.cast(point.getSignature()).getMethod();         String mName = method.getName();         String cName = method.getDeclaringClass().getSimpleName();         LOGGER.log(Level.INFO, "Entering {0}:{1}", new Object[]{cName, mName});         Object out = null;         try {             out = point.proceed();         } catch (Throwable t) {             logExceptions(t, point);         }         LOGGER.log(Level.INFO, "Exiting {0}:{1}", new Object[]{cName, mName});         return out;     }      private void logExceptions(Throwable t, final ProceedingJoinPoint point) {         final Method method                 = MethodSignature.class.cast(point.getSignature()).getMethod();         String mName = method.getName();         String cName = method.getDeclaringClass().getSimpleName();         Object[] params = point.getArgs();         StringBuilder sb = new StringBuilder();         sb.append("Exception caught for [");         sb.append(cName);         sb.append(".");         sb.append(mName);         for (int i = 0; i

How to use it

@Audit   public void testMethod(Int a,int b, String c){ }

Maven dependencies Compile

    org.aspectjaspectjrt1.8.7

Weaving

        com.jcabijcabi-maven-plugincompileajc

转载请标明出处:How to use AOP with AspectJ for logging?

文章来源: How to use AOP with AspectJ for logging?

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aspectj

aop