How to create custom java annotation to log method parameters

Question

I am writting JavaEE application and I would like to use and create custom annotation, which will log data, when annotated method will be called. All I would like to do is, that when annotated method is called, code iterate through all passed method parameters and writes to standard output parameter keys and values.

Some example:

public class Test {

    @LogMethodData
    public int sum(int first, int second) {
        return first + second;
    }
}

I would like to achieve, that when a custom metod will be annotated with @LogMethodData, that code behind will take care and log passed method parameters to standard output (something like "Method data: first - 4, second - 5" if parameter first contains value 4 and parameter second contains value 5), independent from number of passed parameters to methods.

I would be very happy if someone could help me with that, because I have been already searching for a solution, but I didn't found anything usefull. And last, I am not familiar with this things.

Regards, Dahakka

Answer 1

There is no need to define your own Annotation, you can use the @Interceptors Annotation in the EE Container as explained here.

@Interceptors(LoggingInterceptor.class)

Within the Interceptor you'll get a Context that contains your Parameters

public class LoggingInterceptor {
    ...

    @AroundInvoke
    public Object modifyGreeting(InvocationContext ctx) throws Exception {
        ....
        Object[] parameters = ctx.getParameters();
        try {
            return ctx.proceed();
        } catch (Exception e) {
            logger.warning("Error calling ctx.proceed in modifyGreeting()");
            return null;
        }
    }
}

another example : here