[jboss-as7-dev] json vs custom parser

[David M. Lloyd]

On 02/01/2011 06:51 PM, Scott Stark wrote:
> Just browsing through the as7-dev list I don't see a discussion of why
> we have a custom parser for a json like serial format vs just using
> json. Was this to avoid a runtime dependency, or was there another reason?

The DMR was designed to meet the needs we have, in terms of types (JSON 
is limited in that it does not support decimal types, longs, or binary 
blobs, not to mention value types [to allow self-description], and other 
types which we use like pairs are not well-supported).

The use of JSON-like model for DMR was really coincidental.  Now we 
*could* use JSON but I don't really see the need to compromise a modest 
amount of usability for a small amount of "standard-ish-ness".  For 
example one could say the model is also Perl-ish.

Though my voice may not be in the majority, it is my believe that most 
of the management clients in use will either be Java, or command-line 
scripting languages like python and perl either using our command-line 
interface via shell, or via interface to JBoss Remoting (I have planned 
a Perl 5 client for JBoss Remoting, in my copious amounts of free time).

The thing to note is that the JSON-like serialization format is NOT the 
primary interface for serializing DMR; the binary protocol is more 
efficient, simpler and faster to parse, and cross-platform compatible 
(more so than the equivalent JSON - even to JavaScript - because using a 
simple binary parser [and I do mean _simple_] you can support the full 
range of DMR types, not just JS primitive types).  DMR nodes implement 
Externalizable but can also be written to any OutputStream.

IMO, the only reason we have a JSON parser/deparser at all is that 
_some_people_ (whom I will not name) think it's better because it's 
"standard-y" and seems easier to interface.  I have a suspicion that the 
binary protocol will supercede JSON in all use cases, including JS 
clients, due to performance and correctness reasons.  Though the burden 
is likely to fall on me to prove that. :)
-- 
- DML