Get method arguments using Spring AOP?

Question

I am using Spring AOP and have below aspect:

@Aspect
public class LoggingAspect {

    @Before("execution(* com.mkyong.customer.bo.CustomerBo.addCustomer(..))")
    public void logBefore(JoinPoint joinPoint) {

        System.out.println("logBefore() is running!");
        System.out.println("hijacked : " + joinPoint.getSignature().getName());
        System.out.println("******");
    }

}

Above aspect intercepts addCustomer method execution. addCustomer method takes string as an input. But I need to log input passed to addCustomer method inside logBefore method.
Is it possible to do so ?

Answer 1

You have a few options:

First, you can use the JoinPoint#getArgs() method which returns an Object[] containing all the arguments of the advised method. You might have to do some casting depending on what you want to do with them.

Second, you can use the args pointcut expression like so:

// use '..' in the args expression if you have zero or more parameters at that point
@Before("execution(* com.mkyong.customer.bo.CustomerBo.addCustomer(..)) && args(yourString,..)")

then your method can instead be defined as

public void logBefore(JoinPoint joinPoint, String yourString) 

Answer 2

Yes, the value of any argument can be found using getArgs

@Before("execution(* com.mkyong.customer.bo.CustomerBo.addCustomer(..))")
public void logBefore(JoinPoint joinPoint) {

   Object[] signatureArgs = thisJoinPoint.getArgs();
   for (Object signatureArg: signatureArgs) {
      System.out.println("Arg: " + signatureArg);
      ...
   }
}

Answer 3

If you have to log all args or your method have one argument, you can simply use getArgs like described in previous answers.

If you have to log a specific arg, you can annoted it and then recover its value like this :

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
public @interface Data {
 String methodName() default "";
}

@Aspect
public class YourAspect {

 @Around("...")
 public Object around(ProceedingJoinPoint point) throws Throwable {
  Method method = MethodSignature.class.cast(point.getSignature()).getMethod();
  Object[] args = point.getArgs();
  StringBuilder data = new StringBuilder();
    Annotation[][] parameterAnnotations = method.getParameterAnnotations();
    for (int argIndex = 0; argIndex < args.length; argIndex++) {
        for (Annotation paramAnnotation : parameterAnnotations[argIndex]) {
            if (!(paramAnnotation instanceof Data)) {
                continue;
            }
            Data dataAnnotation = (Data) paramAnnotation;
            if (dataAnnotation.methodName().length() > 0) {
                Object obj = args[argIndex];
                Method dataMethod = obj.getClass().getMethod(dataAnnotation.methodName());
                data.append(dataMethod.invoke(obj));
                continue;
            }
            data.append(args[argIndex]);
        }
    }
 }
}

Examples of use :

public void doSomething(String someValue, @Data String someData, String otherValue) {
    // Apsect will log value of someData param
}

public void doSomething(String someValue, @Data(methodName = "id") SomeObject someData, String otherValue) {
    // Apsect will log returned value of someData.id() method
}