Hi all,
after some time it seems that this proposal is getting nowhere, and
would anyway require some time I don't have right now nor plan to have
in the near future.
I am then going to delete the outdated 2_0_NO_JAXB branch.
Regards.
On 06/07/2016 09:39, Francesco Chicchiriccò wrote:
Hi,
FYI I am currently experimenting with some different approaches about
generating the missing XSD for WADLGenerator:
1. use Javassist for adding JAXB annotations to POJOs and then
generating XSD (to be passed as parameter to WADLGenerator) via JAXB;
it is kind of working, but (a) there are things that cannot be easily
inferred (as Map support) and (b) the JAXB annoations might require
tweaking in order to produce results similar to the effective XML
payloads as generated by Jackson
2. generate XSD with Apache XmlSchema having swagger.json (output of
Swagger2Feature) as input; it is working but (a) there are some
missing bits, especially with POJO inheritance and (b) again the XSD
entities do not map 100% with effective XML payloads as generated by
Jackson
3. use jackson-module-jsonSchema [5] to natively generate JSON
schemas out of POJOs, then translate into XSD via Apache XmlSchema (I
am asking for support about this at the jackson-user ML [6])
This last approach seems the most promising to me, especially because
I expect it to generate the schema information most adherent to
Jackson's XML payload representation.
Once completed my reference implementation, I will need to asses
whether it is better to extend the CXF WADLGenerator to incorporate
it, or instead to add a new Maven plugin to Syncope source tree for
XSD generation, and then pass such XSD to the standard WADLGenerator.
I'll keep you posted.
Regards.
[5] https://github.com/FasterXML/jackson-module-jsonSchema
[6] https://groups.google.com/d/msg/jackson-user/4HzGsfRgIz4/YzpNugpcBgAJ
On 05/07/2016 18:30, Sergey Beryozkin wrote:
Hi Francesco
thanks, see comments inline
On 05/07/16 16:50, Francesco Chicchiriccò wrote:
Hi Sergey,
thanks for your comments.
See my replies in-line.
Regards.
On 05/07/2016 14:25, Sergey Beryozkin wrote:
Hi Francesco
Here are some thoughts/comments.
The question is and I guess this is something the team will need to
decide upon is how important having a WADL representation for Syncope
is. Having WADL without a schema is probably not worth it - the UI
View is incomplete as a result and if someone tries to generate a
client from this WADL it won't work either. But then if no-one is
working with WADL on the client or really depending on Syncope WADL UI
View then may be it is a feature that can be let go easily enough.
AFAICT, I haven't heard about anyone generating non-Java classes from
Syncope WADL, and so the most important usage that Syncope users
make of
WADL is via the REST reference documentation available which every
deployment at at
http://syncope.apache.org/rest/2.0/index.html
Without information from XSD, I agree that even the pure documentation
purpose of WADL fades off.
Yes
So, suppose you have decided to let it go.
Then it all looks nice, indeed, having a uniform set of annotations is
advantageous.
But the absence of a schema can be a bit problematic if the
interoperability with the non Java XML clients is required. May be
everyone uses Syncope clients, but if not, then without a schema it
can be tricky for such clients to get the beans generated, etc.
Perhaps it is not going to be a problem because as far as I know only
WADL has a schema and I'm not sure if anyone in the Syncope community
has ever tried this schema to get the non-Java POJOs generated.
As said above, I don't think this could be an issue anyway - at least,
no one has reported about such usage.
Indeed
By the way, I believe you may be able to use JAXB without the
annotations, with the help of JAXBElement. Perhaps might be worth
doing a quick try with Moxy JAXB - it might be able to deal better
with some of the JAXB issues.
Could you please elaborate on JAXBElement? Do you mean we could process
the POJOs, generate the XSD offline and then pass it to WADL? We would
probably solve the documentation issue, but the effective XML objects
built via Jackson would likely differ from this XSD content.
I only meant that one can configure CXF JAXBElementProvider with a
'marshallAsJaxbElement' property and it should work without the JAXB
annotations. I forgot about the schema issue though, sorry.
So I suppose if you are happy with Jackson XML and dropping WADL is
acceptable then do give it a try :-) You can always revert back to
JAXB without affecting the clients too much.
Well, not the clients using JSON nor the ones using XML but via the
Syncope client library, at least.
Oh yes, re WADL and manually supporting the schemas. May be it can be
somehow done such that if a new property is added to one of the
Syncope POJOs then a 'red flag' is raised at the build time if the
schema document has not been synced. That would solve the issue of
maintaining the schema without depending on JAXB all the time, but it
is porbably impossible to implement
Hum, I don't like very much the idea of manually keeping a second
set of
information which needs to be kept in sync with the actual classes...
I agree
Thanks, Sergey
On 05/07/16 11:02, Francesco Chicchiriccò wrote:
Hi all,
Syncope core is currently enabled with REST services which are
available
to work with both JSON and XML payloads; JSON support is provided via
Jackson, XML via JAXB.
The recent SYNCOPE-884 brought again to my attention how difficult
is to
keep supporting both formats, especially considering that often JAXB
does not provide anything special out-of-the-box (take the fix for
SYNCOPE-884 [1] as an example of such troubles).
Hence, I went forward and provided a feature branch [2] where JAXB is
compltely removed and XML payloads are instead managed via Jackson
[3].
At present all tests are running fine, both with application/json and
application/xml and the Swagger UI extension is working as well.
The benefits to me are: (1) manageability (no need to maintain two
different sets of annotations) and possibly (2) performance - even
though I realize that probably the vast majority is using
application/json.
The only problem I can see, instead, is related to WADL: CXF's
generator
relies on JAXB for providing the <grammars> section, so currently no
grammar is available and, as a consequence, there are no links to
payload objects definition in the REST services documentation, as
instead shown at [4].
To given an idea, when you go to [4], click on "numbers", then "GET
(numbers)", you will see a modal window with a table under "Response"
which shows a "syncope1:numbersInfo" link, bringing to the XSD
reference
of such object.
In [2], no link is shown.
There is the possibility of passing an existing XSD file to the WADL
generator, but then the problem of generating such XSD file via
Jackson
arises, which is something I couldn't find a way to.
Questions:
1. how do you see this feature (e.g. removing JAXB) in general?
2. do you think that missing XSD from WADL is grave, considering that
Swagger provides much more and is still working fine?
3. any clever idea about pre-generating the XSD file from a bunch of
Jackson-annotated POJOs?
Regards.
[1] https://git-wip-us.apache.org/repos/asf?p=syncope.git;h=4f6818b
[2]
https://git-wip-us.apache.org/repos/asf?p=syncope.git;a=tree;h=refs/heads/2_0_NO_JAXB
[3] https://github.com/FasterXML/jackson-dataformat-xml
[4] http://syncope.apache.org/rest/2.0/index.html
--
Francesco Chicchiriccò
Tirasa - Open Source Excellence
http://www.tirasa.net/
Member at The Apache Software Foundation
Syncope, Cocoon, Olingo, CXF, OpenJPA, PonyMail
http://home.apache.org/~ilgrosso/
