RFR: make FieldLayout#data() public

[Aleksey Shipilev]

On Wed, 10 Nov 2021 08:26:28 GMT, Ivan Ponomarev <duke at openjdk.java.net> wrote:

> > Can you pseudo-code or point the usage example?
> 
> ```
> for (FieldLayout fieldLayout : ClassLayout.parseClass(obj.getClass()).fields()) {
>             Field f = fieldLayout.data().refField();
> 
>             Object v = ObjectUtils.value(obj, f); //primitives are wrapped, type information lost!
> 
>             //We need everything that can be extracted from Field...
>             refField.getAnnotations()... //e.g. paint the field a specific color
>             refField.getGenericType()... //e.g. label the field with type information
> 
>             if (refField.getType() is primitive or can be treated as primitive per LJV setup){
>                 //treat the value as primitive...
> 
>             } else {
>                 //walk further the object's graph...
>             }
>         }
> ```

It looks to me that this code tries to do the iteration that `GraphLayout.parseInstance` already does. Maybe you just want to extend `GraphWalker` to get this walk?

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PR: https://git.openjdk.java.net/jol/pull/19