Please see comments inline.
Raymond
----- Original Message -----
From: "Jean-Sebastien Delfino" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Saturday, November 17, 2007 9:59 AM
Subject: Re: Data transformation from/to POJO
Raymond Feng wrote:
Hi,
With the recent development of the online store tutorial, we encounter
quite a few issues around the transformation between POJO and other
databindings (such as XML, JSON).
Yeah :)
Let's take the POJO <--> XML as an example. Here is a set of questions to
be answered.
1) Do we require the POJO to be a strict JavaBean or free-form class?
2) How to read properties from a java object?
The data in a java object can be accessed by the field or by JavaBean
style getter methods. There are different strategies:
a) Always use JavaBean-style getter method
b) Always use field access
c) A combination of a & b
The other factor is the modifier of a field/method defintion. What
modifiers are allowed? public, protected, default and private?
If a property only have getter method, should we dump the property into
the XML? How about transient fields?
3) How to write properties to populate the target POJO instance?
a) Use JavaBean setter?
b) Use field
c) Combination of a & b
Can't we just follow the SDO or JaxB spec?
I don't think that's the case. Both SDO and JAXB have addtional metadata to
help make the decision but POJOs don't. SDO has the Type/Property while JAXB
uses annotations.
When we convert XML element back to a POJO property, how do we
instantiate the property instance if the property type is an interface or
abstract class?
For example,
package com.example;
public class MyBean {
private MyInterface p1;
public void setP1(MyInterface p1) {
this.p1 = p1;
}
public MyInterface getP1() {
return p1;
}
}
This goes beyond simple POJOs.
Are you saying we shouldn't support that? One simple case would be how do we
marshal an Exception into XML.
Do we require the XML element contains xsi:type attribute which will be
generated from POJO-->XML to represent the concrete property type? Such
as:
<myBean xsi:type="ns1:MyBean" xmlns:ns1="http://example.com/";>
<p1 xsi:type="ns2:MyInterface" xmlns:ns2=http://example.com//>
</myBean>
Is the idea to support inheritance?
Yes.
--
Jean-Sebastien
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