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I am using Resteasy and GWT. For certain reasons, as many others have similar motivations, I am not using GWT-RPC for some of the functionality of the software I am working on.

I need to pass POJOs between GWT client and server by marshalling/demarshalling the POJOs into/from JSON.

OK, easier said than done because I need the POJO-JSON converters on both sides to match.

Q1. Is there a standard POJO notation in JSON? Is there an ietf RFC or ISO or ECMA that specifies the format of POJO notation in JSON? Or is it a free for all, libertarian anarchy?

Q2. Do Jettison and Jackson (when used with JAXB) and Autobeans produce the same JSON for POJOs?

Q3. This is the most crucial question. You can ignore the other questions above but you MUST answer this. Give me a combination pair of server-side and GWT client side JSONizer/deJSONizer that works together. For example, can I use Autobeans on client-side and use JAXB-jettison on server side and expect the JSONized POJO notation to be the same?

Q4. Is it possible to use JAXB-Jettison or JAXB-Jackson on GWT client-side by including the java source code for JAXB, Jettison/Jackson in the whatever.gwt.xml file? Are there parts of JAXB, Jettison/Jackson source code that might e.g., depend on reflection, or non-serializable, etc that would not make it possible to use JAXB + Jettison/Jackson in GWT client code? If possible, please explain how?

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I should clarify concerning Q1:

I am not asking about RFC for JSON. I am asking about JSON POJO format. When a POJO is converted to JSON, everybody does it their own way - so, I am thinking that there should be an RFC to standardise the way and format a POJO is converted to JSON. Is there a standard or not? !!I hope your answers should not quote me the RFC for JSON!!

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What about

Someone needs to tell me about

  • badgerfish on GWT client
  • and GWT client-server matched JSON-RPC.
Blessed Geek
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  • On using Jettison/Jackson on client side: Jettison does not use reflection itself, just needs Stax API (from JDK 1.6, or separate jar for 1.5). But JAXB makes heavy use of reflection, annotation introspection. Similarly, Jackson requires reflection, annotations, to do bean property auto-detection. I haven't done GWT development so I can not say how big of a problem this might be; sounds like it could be problematic. – StaxMan Aug 09 '11 at 17:34

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JSON is just a subset of JavaScript, it was "invented" by Douglas Crockford. Here is the RFC for application/json: http://www.ietf.org/rfc/rfc4627.txt?number=4627. So any of your server side solutions should create the same result.

We are using RestyGwt ( http://restygwt.fusesource.org/ ) on the clientside and it works like charm. Its JSON encoding style is compatible with the default Jackson Data Binding so it should work with Jackson as well.

Andreas Köberle
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There is no standard for mapping, but I would claim there is obvious simple mapping, given simplicity of JSON format, and de facto standard of Java Beans (i.e. mapping of set/get methods to logical property names). One of few exceptions is Jettison.

Jettison is not as much a JSON/POJO library as it is JSON<->XML library: it converts JSON to XML API calls (and vice versa), to allow use of XML tools such as JAXB for XML data binding, on JSON. But the cost here is that JSON it produces and consumes has extra complexity which is only needed to work with XML APIs. And this is what makes it non-standard compared to the usual straight-forward bindings like used by Jackson, GSON, Flex-json and other "native" JSON libs.

I would recommend not using Jettison unless you really, really must for some reason. Not even if you produce both XML and JSON -- usually you are better off mapping JSON to/from POJOs using JSON tools, and XML separate to/from POJOs (using JAXB etc).

Jettison was intended to bridge the gap between (then) more mature XML tools and newish JSON format. But there isn't much benefit nowadays when there are dozens of mature JSON libraries available.

StaxMan
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  • Thanks for the answer. However, I am writing some trial code with jboss jaxb json badgerfish which seems to require jettison jar (why?). Badgerfish format is simple enough. – Blessed Geek Aug 08 '11 at 03:48
  • Yeah, alas, badgerfish does produce bastardized json so it will probably not work with other libs. But if you can use Jettison on both sides it'll work. Reason JAXB requires it is that it's an XML library, so to produce/consume JSON something else is needed. FWIW, Jackson can use JAXB annotations as well although it does not support JAXB API. – StaxMan Aug 08 '11 at 03:50