Recursive BeanUtils.describe()

Question

Is there a version of BeanUtils.describe(customer) that recursively calls the describe() method on the complex attributes of \'customer\'.

class Customer {

         


        

Answer 1

The challenge (or show stopper) is problem that we have to deal with an object graph instead of a simple tree. A graph may contain cycles and that requires to develop some custom rules or requirements for the stop criteria inside the recursive algorithm.

Have a look at a dead simple bean (a tree structure, getters are assumed but not shown):

public class Node {
   private Node parent;
   private Node left;
   private Node right;
}

and initialize it like this:

        root
        /  \
       A    B

Now call a describe on root. A non-recursive call would result in

{parent=null, left=A, right=B}

A recursive call instead would do a

1: describe(root) =>
2: {parent=describe(null), left=describe(A), right=describe(B)} =>
3: {parent=null, 
     {A.parent=describe(root), A.left=describe(null), A.right= describe(null)}
     {B.parent=describe(root), B.left=describe(null), B.right= describe(null)}}

and run into a StackOverflowError because describe is called with objects root, A and B over and over again.

One solution for a custom implementation could be to remember all objects that have been described so far (record those instances in a set, stop if set.contains(bean) return true) and store some kind of link in your result object.