My contribution to the ongoing trend of reinventing the entire XML toolchain for JSON is a pair of Perl libraries which allow JSON to be produced and consumed in a streaming manner, rather than requiring the data to be represented as a complete, in-memory data structure.
For many applications a traditional on-shot JSON library is more than sufficient, but a streaming JSON parser might be useful if you already know what data structure you're expecting because you can skip over or reject parts of the data that do not conform to the expected structure without them ever manifesting as real objects in your program.
The JSON generator has more limited utility but might be useful for serializing large data structures without them needing to exist in memory in their entirety: you can load data in stages, producing the relevant output and then freeing the memory before moving on to the next part.
Much as with a streaming XML library, the programming model is more awkward than with a library that loads everything into memory, but as JSON becomes the web's de-facto data serialization I think having the ability to stream it will be important for more and more applications.
I'd love to see others implementing similar functionality for other languages, hopefully with a similar API. When it comes to Perl, you can download JSON::Streaming::Reader and JSON::Streaming::Writer from CPAN today. The latest versions, 0.03 and 0.02 respectively, are winging their way through the CPAN indexer as I write this.
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