Okay, here's ideally the scenario I have/want:
I need JSON in a particular format where it looks like the following:
{ "items" : [{"field1":"one", "field2:"two"}, {"field1":"one",
"field2:"two"}] }
or { "items" : [] } when the list is empty
I'm not too particular about the XML output as we don't have any
requirements for it, just is a nice bonus for taking this approach, but I'll
include them as well:
<response>
<item><field1>one</field1><field2>two</field2></item>
<item><field1>one</field1><field2>two</field2></item>
</response>
and
<response/> for empty list
Our class looks like:
@XmlRootElement(name = "response")
public class Items {
@XmlElement(name = "items")
public List<Item> items= new ArrayList<Item>();
}
This works for when the list has 1 or more items, but returns "null" when
the list has 0 items (instead of { "items": [] })
This makes sense though when you look at the XML being produced (which is
what the JSON is based off of). I really probably would want the XML to
look more like:
<response>
<items>
<item><field1>one</field1><field2>two</field2></item>
<item><field1>one</field1><field2>two</field2></item>
</items>
</response>
and
<response><items/></response>
So, a simple change to the class:
@XmlElement(name = "items")
public List<Item> items= new ArrayList<Item>();
becomes
@XmlElementWrapper(name = "items")
public List<Item> items= new ArrayList<Item>();
However, the JSON becomes:
{ "items" : [{ "item" : {"field1":"one", "field2:"two"}}, { "item" :
{"field1":"one", "field2:"two"}}] }
or { "items" : [ null ] } when the list is empty
So it seems there are a few approaches I could take:
1) Add a null Item when the list is empty in order to produce some XML - not
ideal
2) Enable more than just root unwrapping in the XmlElementWrapper case where
I can unwrap the items in the list - sounds better
3) Try the JacksonProvider and separate JSON generation from XML
generation... not considered this before this email...
Does that make any sense? Thoughts?
Andy O
On Wed, Mar 11, 2009 at 5:10 AM, Jakub Podlesak <Jakub.Podlesak_at_sun.com>wrote:
> On Tue, Mar 10, 2009 at 01:45:11PM -0600, Andrew Ochsner wrote:
> > Sorry, one more unfortunate update.
> >
> > Using XmlElementWrapper, while gets us closer to correct JSON (and looks
> to
> > be correct XML) it really messes things up for us in JSON when there are
> > elements in the array where it looks like :
> > { "items": { "item": {}, "item":{} }
>
> I suppose the issue now lays in the Item bean,
> since it's content is not being written.
>
> How the XML looks like?
>
> Could you give a quick try with something like:
>
> @XmlRootElement
> public class Item {
>
> public String field1 = "one";
> public String field2 = "two";
> }
>
> And second thing: the JSON above is incorrect, you should not have
> two "item" objects encapsulated in the same container object,
> how did you get it? Default mapped convention?
>
> And i am also a bit confused with your desired JSON format, since
>
> {"items":[{"field1":"val1","field2":"val2"}] differs from
> {"items":[{"item":{"field1":"val1","field2":"val2"}}]
>
> Could you please clarify? I mean, could you give us some examples
> of JSON exprs you need to get generated?
>
> And the last thing: If i understand it correctly: you do need both XML and
> JSON generated, right?
>
> Thanks,
>
> ~Jakub
>
>
>
> >
> > So, we really have an issue here. And the hack solution really defeats
> the
> > purpose for us as we want to generate documentation based on the code (as
> > opposed to javadoc which can and will get out of sync). We can't infer
> much
> > from a Response return value.
> >
> > Thanks
> > Andy O
> >
> > On Tue, Mar 10, 2009 at 10:20 AM, Moiz Dohadwala <
> mdohadwala_at_mokafive.com>wrote:
> >
> > > Hello,
> > >
> > >
> > >
> > > Thank you all for your suggestions. I had tried out the annotations
> > > suggested below without success prior to posting to the mailing list.
> Right
> > > now, due to time pressure, I have implemented the following ugly hack:
> > >
> > >
> > >
> > > If( rows.getTotalCount() == 0 )
> > >
> > > {
> > >
> > > return Response.ok(“{rows:[], totalCount:0}”).build();
> > >
> > > else
> > >
> > > {
> > >
> > > return Response.ok(rows).build();
> > >
> > > }
> > >
> > >
> > >
> > > This seems to have tied me over for now.
> > >
> > >
> > >
> > > I would suggest changes to the JSONConfiguration.arrays() api to
> specify
> > > forcing of the empty arrays.
> > >
> > >
> > >
> > > -Moiz
> > >
> > >
> > >
> > > *From:* aochsner_at_gmail.com [mailto:aochsner_at_gmail.com] *On Behalf Of
> *Andrew
> > > Ochsner
> > > *Sent:* Tuesday, March 10, 2009 8:49 AM
> > > *To:* users_at_jersey.dev.java.net
> > > *Subject:* Re: [Jersey] RE: array handling in JAXB to JSON conversion
> > >
> > >
> > >
> > > So, a little update because I'm running into the same issue, except I'm
> > > using the natural mapping.
> > >
> > >
> > > Various combinations of required=true/false and nillable = true/false
> have
> > > not helped. In fact, when getting as XML, the <items/> element is not
> > > getting written out. So that's a JAXB thing.
> > >
> > > So I'm trying the XmlElementWrapper, and it's close. The XML does spit
> out
> > > <items/> which is good, but the JSON is { "items":[null] } which
> doesn't
> > > seem to be the same as { "items":[] } which is what I want.
> > >
> > > HTH
> > > Andy O
> > >
> > > On Mon, Mar 9, 2009 at 10:39 AM, Jakub Podlesak <
> Jakub.Podlesak_at_sun.com>
> > > wrote:
> > >
> > > On Mon, Mar 09, 2009 at 05:10:19PM +0100, Paul Sandoz wrote:
> > > > Hi Jakub,
> > > >
> > > > Do you mean that JAXB is not writing out any start element for
> "items"
> > > > because the value of the items field is null or empty?
> > >
> > > Hmmm, you are right, jaxb should generate at least <items/>, which
> should
> > > IIRC get
> > > translated into "items":null for the default mapped convention.
> > >
> > > Need to check this out, and then will report back here.
> > >
> > > ~Jakub
> > >
> > >
> > >
> > > >
> > > > There may be an annotation to force JAXB to always write out "items":
> > > >
> > > > 1) using c; or
> > >
> > > >
> > > > 1) using XmlElementWrapper, the JavaDoc states:
> > > >
> > > >
> > >
> http://java.sun.com/javase/6/docs/api/javax/xml/bind/annotation/XmlElementWrapper.html
> > > > The two serialized XML forms allow a null collection to be
> represented
> > > > either by absence or presence of an
> > > > element with a nillable attribute.
> > > >
> > > > or it may be possible to utilize XmlJavaTypeAdapter.
> > > >
> > > > Paul.
> > > >
> > > > On Mar 9, 2009, at 4:47 PM, Jakub Podlesak wrote:
> > > >
> > > >>
> > > >> Hi Moiz,
> > > >>
> > > >> You have hit an edge case, and i am afraid i have no good news for
> you.
> > > >> Jersey JSON provider takes what JAXB gives out, and the information
> > > >> about the emtpy array is obviously missing.
> > > >>
> > > >> One option would be to try out the provider mentioned by Tatu.
> > > >> Have you had a chance to test it yet?
> > > >>
> > > >> Another option would be to use the low-level JSONObect/JSONArray
> > > >> providers (used in bookmark example [1].
> > > >>
> > > >> ~Jakub
> > > >>
> > > >> [1]
> > >
> http://download.java.net/maven/2/com/sun/jersey/samples/bookmark/1.0.3-SNAPSHOT/bookmark-1.0.3-SNAPSHOT-project.zip
> > > >>
> > > >>
> > > >> On Fri, Mar 06, 2009 at 07:21:51AM -0800, Moiz Dohadwala wrote:
> > > >>> I have tried that too, but hasn't worked either.
> > > >>>
> > > >>> -Moiz
> > > >>>
> > > >>> From: Wilhelmsen Tor Iver [mailto:TorIverW_at_arrive.no]
> > > >>> Sent: Friday, March 06, 2009 5:01 AM
> > > >>> To: users_at_jersey.dev.java.net
> > > >>> Subject: Re: [Jersey] RE: array handling in JAXB to JSON conversion
> > > >>>
> > > >>> Try adding required=true to this:
> > > >>>
> > > >>> @XmlElement(name="items")
> > > >>> List<Item> items;
> > > >>>
> > > >>> or else tell JAXB to treat nulls and empty collections differently.
> We
> > > >>> ran into the same issue where null/empty elements were absent from
> the
> > > >>> XML and thus a JAXB client would generate classes missing these
> > > >>> properties.
> > > >>
> > > >>
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