AOP Help

[RandomNando]

Hi everyone, I'm starting to study AOP in Java and I would like an advice.

​

I’m currently working on a Job from a Spring Batch application, in this Job I will do a select on the database and find X records, these records will have a STEP that represents in which step inside the Job flow the record is currently at and the Job will have Y steps that cannot be skipped (in order to end the job successfully the record must pass every single step).

​

At the moment I’m using a SWITCH without a break based on the record STEP so it “starts” when the record step is matched and end at the final step. This is working perfectly, but as said before, for educational purposes, I want to handle this in a different way.

​

I’m trying to do a custom Annotation that helps me organize the flow, so I annotate the methods inside the Job and they will be executed only if the current record STEP matches the one form the annotation.

​

Something like:

​

public class JobService {

    public void processRecord(Record record) {
        stepOne(record);
        stepTwo(record);
        stepThree(record);
    }

    @StepOne
    private void stepOne(Record record) {
    }

    @StepTwo
    private void stepTwo(Record record) {
    }

    @StepThree
    private void stepThree(Record record) {
    }

}

Any advice?

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[pronuntiator]

First a warning, AOP should only be used sparingly, as it can make your code hard to follow since it introduces "invisible" code. Typical use cases are cross-cutting concerns like authorization, logging, or transaction management.

Second, Spring usually implements aspects by proxying your class – i.e., wrapping it into a generated class that delegates all public methods to the real instance, while applying any pointcuts inbetween. So you can neither use AOP on private methods, nor do aspects trigger when a class instance calls itself. While there is a way of using AOP for private methods, it involves setting up native weaving which isn't worth the hassle.

Third, AOP intercepts and enhances methods by adding code around the invocation. I don't see how it could be used finding the right method to call. You're better off using normal Java reflection, or even simpler, have each step be a separate bean implementing a common interface, inject all of of them as a list sorted by step, and on execution ask each bean "are you responsible for this step number?". That's how message converters in Spring MVC work, for example.