Java Annotation or Code Generation

Question

Give a nested class definition

class A {
   B b;
   public B getB() {
       return b;
   }
}

class B {
   ArrayList<C> list;
   public getListC() {
    return list;
  }
}

class C {
  D d;
  public D getD() {
    return d;
   }
}

class D {
   E e;
   public E getE() {
       return e;
    } 
}

Now let's say that I have an Instance of Class A and I want to get access to an instance of E through A's instance like following

E someMethod(A a) {
    if (a == null
       || a.getB() == null
       || a.getB().getListC() == null
       || a.getB().getList().isEmpty()
       || a.getB().getList().get(0) == null
       || a.getB().getList().get(0).getD() == null) {
       return null;
     }
    return a.getB().getList().get(0).getD().getE();
}

Now I want to know if there is a way to automatically genererate the above code using Annotation or some other tool so that I don't have to repeaditly write such a code. I should only be doing following

E someMethod(A a) {
    @AwesomeAnnotation(a.getB().getList().get(0).getD().getE());
}

whatever the annotation would be (which I am unaware of) the input would cause NullPointerException — Sharon Ben Asher
– Sharon Ben Asher, Commented Mar 29, 2018 at 13:41
You should consider using Optionnals, it's going to be easier than code generation. Also think about whether or not it make sense for these objects to be null, if not then using defaults value might be a better solution. — Nyamiou The Galeanthrope
– Nyamiou The Galeanthrope, Commented Mar 29, 2018 at 13:41
Java has method references, you may want to write a method that do what you want. getOptional(a,A::getB,B::getC,C::getD,D::getE)? — user202729
– user202729, Commented Mar 29, 2018 at 13:55
@Derlin catch of NPE is very dangerous, if you were to replace those simple getter one day with some computation, you could break in the computation and swallow the exception silently. — Nyamiou The Galeanthrope
– Nyamiou The Galeanthrope, Commented Mar 29, 2018 at 14:37

Nyamiou The Galeanthrope · Accepted Answer · 2018-03-29 13:44:07Z

1

KludJe is probably what you want.

answered Mar 29, 2018 at 13:44

Nyamiou The Galeanthrope

1,23410 silver badges23 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Big O Over a year ago

Interesting, Minimum is java 8, I will check if that could work

Big O Over a year ago

Also, do you know if this uses runtime reflection?

Nyamiou The Galeanthrope Over a year ago

No, only using method references (that's why it require Java 8). See here: github.com/mcdiae/kludje/blob/master/kludje-core/src/main/java/…

Collectives™ on Stack Overflow

Java Annotation or Code Generation

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related