[jboss-dev-forums] [Design of POJO Server] - Re: metadata simplication

[wolfc]

We're still mixing merging and parsing logic, which to me looks like an unsolvable puzzle.

What's the function of the override (NamedMetaDataWithDescriptionGroupWithOverride.data)?
Either it's for holding data from the jboss xml parse or it's for referring to the override. IMHO it can't be both.

The code now creates a StackOverflow in JBossEnterpriseBean.setDescriptionGroup. (ensureOverride returns a new instance of the same class and calls setDescriptionGroup.)
I have changed this part, but as long as the above question is unanswered the solution is by definition wrong.

Another thing is the merge method: the current use of the merge is contradicting the implementation.
MergeUtil.merge:
      JBossMetaData merged = new JBossMetaData();
  |       merged.merge(jboss, spec);
  |       merged.setOverridenMetaData(spec);
  |       return merged;
vs for example IdMetaDataImpl:
   public void merge(IdMetaDataImpl merged, IdMetaDataImpl original)
  |    {
  | ...
  |       if (id != null)
  |          merged.setId(id);
  |       else if (original.id != null)
  |          merged.setId(original.id);
  |    }
where merged is the target. I would rather see this as target (as in MergeUtil) and have the following signature:
interface Mergable<M>
  | void merge(M original, M override);
Or maybe only a one-way merge:
interface Mergable<M>
  | void merge(M override);
Because the default (non-performant) code is always:
void merge(M original, M override)
  | {
  |    merge(original);
  |    merge(override);
  | }

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