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https://issues.apache.org/jira/browse/JCR-1259?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12555356#action_12555356
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Jukka Zitting commented on JCR-1259:
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Looks good, though I have some design comments:
1) ItemFilter vs. Predicate
How about using the Predicate interface from commons-collections instead of the
custom ItemFilter interface? Using Predicate would give us things like
ItemFilterList, MatchAllFilter, MatchNoneFilter, and much more for free as well
as working nicely together with our existing Iterator adapters in
o.a.j.commons.iterator.
For example, with Predicate filters you could do something like this to select
all child nodes with the given node type:
NodeIterator iterator = new NodeIteratorAdapter(
new FilterIterator(node.getNodes(), new NodeTypePredicate("my:type")));
Of course you'd need to use instanceof and type casts, but you'd need them in
any case with ItemFilter as the interface takes Items, not Nodes or Properties.
Also, you wouldn't have the "depth" parameter, but I'm not sure it's really
needed (i.e. all the use cases I can think of could be solved with
Item.getDepth()).
2) TreeWalkerListener vs. ItemVisitor
The JCR API already provides a nice implementation of the Visitor pattern in
the ItemVisitor interface and the Item.accept(ItemVisitor) method. Instead of
coming up with an alternative implementation in TreeWalker and
TreeWalkerListener, I'd rather see a set of generic ItemVisitor classes like
DepthFirstItemVisitor, DepthLimitedItemVisitor, BreadthFirstItemVisitor,
FilterItemVisitor, etc. that could be combined together with each other and the
above Predicate filters to implement functionality like in the proposed
TreeWalker and in many other tree traversal cases.
> Utility code for filtering and packaging trees
> ----------------------------------------------
>
> Key: JCR-1259
> URL: https://issues.apache.org/jira/browse/JCR-1259
> Project: Jackrabbit
> Issue Type: New Feature
> Components: jackrabbit-jcr-commons
> Reporter: Carsten Ziegeler
> Attachments: jcr-commons-filtering.zip
>
>
> The attached zip contains new utility code for filtering and packaging trees
> in the repository.
> A tree can be traversed by the provided tree walker. During the traversal
> configurable filters can be applied. The filters have influence on the
> traversal, like skipping nodes or properties.
> Included filters test the node name, node type etc. Custom filters are
> possible as well.
> A tree walker notifies a tree walker listener (interface) whenever it
> traverses an item.
> The second utility code is able to package a whole tree (through a
> description) and export this in some way - the exporter is an interface and
> could e.g. be an exporter serializing the tree into a zip archiv etc.
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