The performance hit isn't too big compared to iterating through the
components. Either with a stream() or a iterator() you're into O(n)
land. Then the O(n + c) where c is some time for the extra method
calls necessary for the stream() becomes negligible. This is
illustrated with the micro benchmark I just ran:
Benchmark Mode Cnt Score
Error Units
retrieveComponentUsingGet thrpt 10 24964809.356 ± 195755.618 ops/s
retrieveComponentUsingIterator thrpt 10 1274221.027 ± 31154.531 ops/s
retrieveComponentUsingStream thrpt 10 1111762.631 ± 8065.395 ops/s
This is with 100 components added to a page, and retrieving component
with id "50" (each component was issued the index as a string as an
id).
As you can see: using iterator or stream doesn't matter that much.
Using the get() is quote optimal, as we use a Map and index based
lookups when n > 30 or so. Therefore it is an order of magnitute
better: it performs at O(1).
Here's the same benchmark, but now with 100,000 components added to the page.
Benchmark Mode Cnt Score
Error Units
StreamVsGet.retrieveComponentUsingGet thrpt 10 25653965.493 ±
268342.736 ops/s
StreamVsGet.retrieveComponentUsingIterator thrpt 10 795.780 ±
27.099 ops/s
StreamVsGet.retrieveComponentUsingStream thrpt 10 756.819 ±
30.469 ops/s
So in my opinion the performance loss is not too bad, at least when
you don't have a component identifier at your disposal.
I would also add two stream() methods:
- one to stream() the direct children of the markupcontainer
- one to hierarchically stream() all children
The second one is competing with visitChildren(), so might be unnecessary.
Martijn
On Sat, Nov 12, 2016 at 7:36 PM, Andrea Del Bene <[email protected]> wrote:
> I did something similar some time ago. The idea is nice but it was abandoned
> due to performance drawbacks as streams are quite slower than regular
> iteration. Anyway, this is what I did
>
> https://github.com/apache/wicket/commit/73ac8c7e6da3ff9dd0244ad66c63944ba3d64c78
>
>
>
> On 12/11/2016 17:56, Martijn Dashorst wrote:
>>
>> In our code I often see code that (ugh) retrieves a component by id,
>> something like:
>>
>> public class SomePanel extends Panel {
>> ...
>> target.add(getPage().get("feedback"));
>> ...
>> }
>>
>> If we made MarkupContainer streamable, we could, in pseudo code, do
>> something like:
>>
>> getPage().stream().filter(c->c.getId().equals("feedback")).findFirst();
>>
>> Which is not better than getPage().get("feedback")
>>
>> But it is more flexible checking for types, etc.
>>
>> The implementation is not that complicated:
>>
>>
>> /**
>> * Returns a sequential {@code Stream} with the children of this
>> markup container
>> * as its source.
>> *
>> * @return a sequential {@code Stream} over the children of this
>> markup container
>> * @since 8.0
>> */
>> public Stream<Component> stream()
>> {
>> return StreamSupport.stream(spliterator(), false);
>> }
>>
>> Good idea?
>>
>> Martijn
>
>
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