> I'd like to address the topic of JSON parsing in Play again.  Just to put
> some hard numbers on this, yesterday, unrelated to play framework, I was
> looking at some code that someone told me was going much slower than
> expected.  It was taking about 120 milliseconds to do something that they
> expected to only take a few milliseconds.  We quickly determined that the
> major part of the issue was that they weren't reusing the Jackson
> ObjectMapper.  Once they reused the Jackson ObjectMapper, the time of this
> thing (including the IO involved in this operation) went down to 5
> milliseconds.  So you can see that creating an ObjectMapper each time you
> need to use it can have a massive performance impact.

> I submitted this pull request, but it was rejected because it made json
> support a "plugin":

> https://github.com/playframework/Play20/pull/225

> Actually, I wasn't interested in making JSON support a plugin, all I wanted
> was the ability to initialise an ObjectMapper on application start,
> and reinitialise it each time the application is updated (in development,
> this is needed, because Jackson might not pick up changes in annotations).
>  The only way I can see for an internal component in play to hook into play
> to do this is to implement the Plugin interface, from where it gets notified
> of application start events.  This is the same way that other core non
> plugin components of Play seem to do it.  In fact, I put the JSON plugin
> into Plays own play.plugins file, which means it's impossible to disable
> it... which means it's not really a plugin at all, it's just using the
> plugin mechanism to hook into application start events.  I would have
> thought this is the sensible way to go about doing that, am I wrong?  If I
> am wrong, what is the correct way for a core play component to hook into
> application start events?

> I also wanted to provide a way to configure the ObjectMapper play uses (for
> example, to register custom serialisers/deserialisers), which also requires
> doing things on application start... and using the Plugin interface seemed
> to be the right way to do this too.

> Also, Scala JSON support is already using a singleton instance, though
> perhaps we want to provide a mechanism for configuring the ObjectMapper in
> Scala, but I think this is a separate issue, because the code bases in both
> the Java and the Scala support are completely different.

> So, should I implement it in some different way, or can my original pull
> request be accepted?

> Cheers,

> James

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