Re: [wsrp-interop] WSRP event payloads with "simple" types

[Kevin Frender <kevin.frender@oracle.com>]

Hello Nader,

I may be misunderstanding your suggestion, but my original statement of 
the problem wasn't entirely clear either.

Yes, I know that JAXB can be set up so that arbitrary objects can be 
marshalled and unmarshalled (as DOM elements), but the problem as I see 
it is that for the simplest of data types explicitly supported by the 
JSR286 spec as event payloads, there is no obvious, inter-operable way 
to marshal these event payloads so that they will be guaranteed to show 
up in the receiving portlet as the same simple type that was sent.

For example, if portlet A sends an event:

eventResponse.setEvent(new QName("namespace", "localpart"), "Simple 
String payload");

and portlet B receives this event, I would expect portlet B to be able 
to do this:

Event event = eventRequest.getEvent();
String payload = (String)event.getValue();
 
-- and not need to do anything like this:

String payload = ((Element)event.getValue()).getTextContent();

The problem isn't that I don't know of any way at all to marshal the 
simple String payload into XML, or how to unmarshal that form back into 
a String, but rather that I don't know how to distinguish between an 
event payload coming from another (third-party) WSRP producer or 
consumer that represents a marshalled simple payload type (like a 
String) versus an event payload that was deliberately configured by the 
portlet developer to be marshalled into XML.  For example, if I get an 
event payload in the WSRP event that looks like this:

<samplePayload>Simple String payload</samplePayload>

I could assume that this means I should return an Event object to the 
portlet developer whose payload is a java.lang.String object, as 
outlined in the sample above.  However, if the portlet developer for 
event-sending portlet "C" actually created their own event payload 
object and gave it a valid JAXB binding, such as:

@XmlRootElement
public class SamplePayload implements Serializable
{
    String value;
    public SamplePayload(String s)
    {
       value = s;
    }
}

eventResponse.setEvent(new QName("namespace", "localpart"), new 
SamplePayload("Simple String payload"));

Then the developer actually intended for a "SamplePayload" object to be 
sent, not a java.lang.String-- and a receiving portlet should probably 
get an XML DOM element in the event payload instead of a simple 
java.lang.String object (assuming that the receiving portlet's WSRP 
implementation doesn't have a JAXB SamplePayload object configured). 

So my proposal would be a set of extension elements for containing only 
the simplest of event payload values-- the simple types explicitly 
supported by the JSR286 specification-- so that various WSRP 
implementations could recognize those elements as containing a simple 
payload value (and ONLY a simple payload value).  I would propose that 
arrays of simple values would not be supported, as they are not 
explicitly supported by the JSR286 spec as payload types, but arrays of 
simple values can still be handled by JSR286 portlet developers by 
specifying their own JAXB bindings.

For example, we might define in the wsrp-extra namespace elements such as:

<element name="stringPayload" type="xsd:string"/>
<element name="intPayload" type="xsd:int"/>
<element name="longPayload" type="xsd:long"/>
...

By being in the WSRP namespace (and being well-known elements) it would 
be easy to distinguish these "simple" event payload types from "complex" 
marshalled objects.  I can create such schema definitions for sending 
simple payload types myself and put them in our proprietary namespace, 
and they would work just fine as long as the events were not delivered 
to a third-party WSRP producer, which wouldn't recognize them as 
intending to be "naked", simple values. 

So that is the point of my post- for at least the simplest of event 
payload types it seems like a WSRP-standard solution for encoding these 
payload types would be beneficial for interop purposes.

   Kevin


Nader Oteifa wrote:
> Kevin,
>
> Any of these links of help?
> 	
> https://jaxb.dev.java.net/tutorial/section_2_2_16_1-Elements-With-Any-Type.h
> tml#Elements%20With%20Any%20Type
>
> https://jaxb.dev.java.net/tutorial/section_2_2_16_2-Another-Content-Tree-as-
> Element.html#Another%20Content%20Tree%20as%20Element
>
> https://jaxb.dev.java.net/tutorial/section_6_2_7_6-Collecting-Unspecified-El
> ements-XmlAnyElement.html#Collecting%20Unspecified%20Elements:%20XmlAnyEleme
> nt
>
> I think dealing with an extension is probably more complex than trying to
> figure out how to make it work with primitive types without having to create
> a class. Do you expand payload to include all primitive types?  What about
> arrays of primitive types? I don't even think namedStringArray should be in
> payload and even in the specification it appeared like it originally was not
> there.
>
> I think you'll have to take the "Any" XML element use it as input to a new
> Unmarshaller but only when the value of the payload is requested with the
> given type.  When marshalling, you'll need to have an extra parameter to
> specify that a root should be created with same name as event or use
> overloaded methods.  Example:
>
>
> int x = myEvent.GetValue<int>(0); //parameter is default value for type 
> myEvent.SetValue<int>(x, true); // parameter = true to create an element
> with same name as event name
>
> or 
>
> int x = myEvent.GetValue(0); //overloaded methods for all primitive types
> myEvent.SetValue(x); //these create the element with same name as event
>
> or some variation on this theme.
>
> Nader
>
> -----Original Message-----
> From: Kevin Frender [mailto:kevin.frender@oracle.com] 
> Sent: Wednesday, October 14, 2009 3:58 PM
> To: wsrp-interop@lists.oasis-open.org
> Subject: [wsrp-interop] WSRP event payloads with "simple" types
>
> Hello all,
>
> For WSRP 2.0 events, the schema-supported event payload types are a 
> NamedStringArray and "any" from a non-WSRP-types namespace.  This was a 
> conscious decision at the time to not get into the details of 
> standardizing event payload encoding.
>
> For JSR286 (Java Portlet specification version 2.0) event payloads can 
> have any JAXB-bindable object type, or any of the JAXB primitive types, 
> which include very basic things like java.lang.String, java.util.Date, 
> etc. which have obvious mappings to XML data types.  The JAXB primitive 
> types don't have @XmlRootElement annotations however, so they can't be 
> marshalled directly (by themselves) to XML.
>
> So if a portlet wanted to send an event with a simple String payload, 
> JSR286 allows that, but there is no obvious way to represent that in XML 
> as a WSRP event payload in a manner that other WSRP containers could 
> recognize.
>
> In the interest of interoperability, I was wondering how everyone 
> handles the binding of these "primitive" types when they are used as an 
> event payload.  We were thinking of creating a simple XML element for 
> holding these types inside the event payload, but that wouldn't work too 
> well for WSRP interoperability, unless the WSRP committee came up with a 
> standard schema and XML namespace to hold these "simple" types.  So as a 
> second question, I was wondering if there was interest in creating a 
> standard WSRP extension for handling these simple data types.
>
> Thanks,
>
>   Kevin
>
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