Hi,
It should be a good fit to use Transfomation service to present property
values in a preferred way indicated by the property receiver.
Here're some use cases I can imagine:
1) Parse the XML for a property value to create a DOM representation (StAX
XMLStreamReader-->DOM Node)
2) Inject the property to the target instance:
For example,
@DataBinding(type="sdo", ...)
@Property
private MyProperty myProperty;
Then DOM Node --> SDO DataObject can be applied.
Thanks,
Raymond
----- Original Message -----
From: "Jim Marino" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Tuesday, July 18, 2006 2:12 PM
Subject: Data binding extensions and changes to the SCA spec
I would like to get started on support for for XPath in SCDL as it is part
of the recent SCA spec changes. This will likely require changes to the
loader infrastructure and in particular StringParserPropertyFactory.
Instead of having a PropertyFactory create an ObjectFactory responsible
for returning a value that is injected into a component implementation
instance, we will need to have a more flexible approach as property values
may now be based off of XPath expressions to composite properties.
What I would like to propose is that we have creation of the
ObjectFactory for the property handled by the builder in much the same
way as it handles wires. I think we can leverage the data transformation
service for this. In this case, the builder will be given a
representation of the parsed XML, probably DOM. If the property value was
an XPath expression, the builder will have to use an XPath engine to
evaluate and retrieve this actual value (Jaxen?) represented as a Node.
The builder will then in turn use the transformation service to create a
"bound type". The builder will subsequently create an ObjectFactory for
the bound type responsible for injecting on the target component
implementation instance. The specific kind of ObjectFactory will depend
on the kind of property it is:
- If it is immutable, the builder will use a SingletonObjectFactory
- If it is mutable, but the property is configured as "safe" (i.e. the
component does not mutate it), the builder will use a
SingletonObjectFactory). We can also assume by default values are "safe"
unless explicitly marked.
- If it is mutable, marked "not safe," and Cloneable, a
CloningObjectFactory is used which clones on getInstance()
-If it is mutable, marked "not safe" and is not Cloneable, the builder
avoids the call to the transformation service and instead uses an
ObjectFactory which calls out the to transformation service on every
getInstance() invoke.
For some implementation types, a builder may not want to use
ObjectFactory (perhaps the implementation just takes a DOM or some other
format). In that case, the builder would be free to use the
transformation service or not.
Raymond, does this sound like it would fit with the transformation
service? If so, I think we need to look at incorporating the base data
transformation framework into SPI and core.
I'd also be willing to work on an XStream binding extension which would
enable handling of basic POJO binding.
Jim
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