Hi Dennis,
I might not explain my needs clearly in my previous post. So let me
clarify it.
The unmarshalling process does not create new instance of Equipment, but
rather link to a previously created one. As you can see from the sample
XML file.
<equipment>
<item>
<phone>Siemens S45</phone>
<quantity>5</quantity>
</item> <item>
<pda>O2 XDA</pda>
<quantity>2</quantity>
</item>
</equipment>
It only describes what type of Equipment each line item associated with,
but not all attributes of each Equipment to construct it (those
someOtherAttrib are not in the XML file). This information will be use
to creates association in EquipmentLineItem object to reference to a
suitable Equipment object - which is already created. This mechanism is
provided by a factory method. That is why I ends up using serializer and
deserializer.
The name attributes in each Equipment instances is required, as it
described the specific unique name of each equipment, not just a type.
For example, I might have an instance of Phone (Phone is a type of
Equipment) with "Siemens S45" as name.
Now I defined the mapping for EquipmentLineItem as follow:
<mapping name="EquipmentLineItem" class="com.waveman.poc.EquipmentLineItem">
<value name="name" field="equipment"
serializer="com.waveman.poc.BindingUtils.toString"
deserializer="com.waveman.poc.BindingUtils.findEquipment"
/>
<value name="quantity" field="quantity" />
</mapping>
Using this mapping achieve my needs, except that element name for
Equipment will always be <name> no matter what type of the equipment is.
What if I want element name of each Equipment type to be different? So
instead of generic <name> tag, I would have <phone>Siemens S45</phone>
for Phone instance and <pda>O2 XDA</pda> for Pda instance. I could not
figure out how to use abstract mapping with the above mapping I
currently have.
Regards,
Vairoj
--__--__--
Message: 4
Date: Fri, 18 Nov 2005 14:06:10 -0800
From: Dennis Sosnoski <[EMAIL PROTECTED]>
To: [email protected]
Subject: Re: [jibx-users] Re: Abstract, structure mapping with multiple elements
(revised)
Reply-To: [email protected]
Hi Vairoj,
I think the approach you want here is not to use a
serializer/deserializer, but rather to list the alternatives in the
EquipmentLineItem <mapping>. You should be able to use an abstract
mapping for the Equipment class as part of this (though I haven't tried
it, and I'm not sure the value with style="text" inside an abstract
mapping is going to work without a hitch):
<mapping name="lineitem" ...>
<structure name="phone" class="...Phone">
<structure map-as="...Equipment"/>
<value style="attribute" name="someOtherAttrib"
field="someOtherAttrib"/>
</structure>
<structure name="pda" class="...Pda">
<structure map-as="...Equipment"/>
<value style="attribute" name="someOtherAttrib"
field="someOtherAttrib"/>
</structure>
...
</mapping>
<mapping class="...Equipment" abstract="true">
<value style="text" name="name"/>
</mapping>
But the way I'd probably handle this myself is to avoid the name in the
Equipment class all together, instead using an abstract getName()
method. Then Phone just implements this:
class Phone extends Equipment {
public String getName() { return "phone"; }
}
Why have a name field, after all, when you want the name to be
determined by the type of equipment?
- Dennis
Vairoj A. wrote:
Hi,
Sorry for a separate post. After posted the message, I managed to find
a way to provide flatten mapping for Equipment using serializer and
deserializer.
So now I have the binding defined as follow:
<mapping name="lineitem"
class="com.waveman.poc.EquipmentLineItem">
<value name="name"
field="equipment"
serializer="com.waveman.poc.BindingUtils.equipmentToString"
deserializer="com.waveman.poc.BindingUtils.stringToEquipment"
/>
<value name="quantity" field="quantity" />
</mapping>
However, I still could not figure out how to have different element
name based on Equipment subclasses. The current binding always map
Equipment to <name> tag under <lineItem> here is the example (which is
not the correct one).
<equipment>
<lineitem>
<name>Siemens S45</name>
<quantity>10</name>
</lineitem>
<lineitem>
<name>O2 XDA</name>
<quantity>5</quantity>
</equipment>
So now, the revised (and hopefully, final) question is, how to define
the binding to have element name different, based on subclasses of
Equipment (like the example XML file in my previous post)?
Regards,
Vairoj
Vairoj A. wrote:
Hi,
After my previous post with suggestion from Dennis, I have
re-evaluate the structure of both domain object and XML with other
application requirements. It is confirm the the domain object has to
remain unchanged. However, the XML structure can be changed.
So the same object model:
class Person {
private Set<EquipmentLineItem> lineItems;
}
class EquipmentLineItem {
private Equipment equipment;
private int quantity;
}
abstract class Equipment {
private String name;
}
class Phone extends Equipment {
private int someOtherAttrib;
}
class Pda extends Equipment {
private String someOtherAttrib;
}
Now, the XML will be look like what Dennis suggested in his reply to
my previous post:
<equipment>
<item>
<phone>Siemens S45</phone>
<quantity>5</quantity>
</item> <item>
<pda>O2 XDA</pda>
<quantity>2</quantity>
</item>
</equipment>
Point to note is that, the binding will not construct Equipment
subclass itself this time. As you can see from the class declaration,
there are some other attributes specific to each subclass. So I would
like to delegate the instantiation of Equipment subclass to a
factory method instead. The factory method returns correct instance
(fully initialized) based on String between <phone> tag or <pda> tag
(i.e. Siemens S45, O2 XDA)
public static Equipment getEquipment(String equipmentName)
Based on the above requirements, I am having 2 issues regarding binding:
1. How can I define the mapping for equipment so that different
subclass map to different element name?
2. I don't seems to make use of factory attribute correctly. While it
use the factory method to create new instance, it still override
values of the instance with one from the XML, which I do not want.
Could you give me a binding example for the situation? I am kind of
stuck now. Thank you very much, I know that the question is not a
short one.
Regards,
Vairoj
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