Re: [castor-user] How to dynamic object resolution in Castor XML mapping files

Mon, 19 Dec 2005 07:20:12 -0800 

Sumanta-
FYI, even if the class isn't in a mapping file, Castor will attempt to introspect it. This doesn't always produce the prettiest XML, but it does try to keep the object model fully populated. 

I'm glad to help.

Stephen


Sumanta Ranjan Das wrote:

Hi Stephen,


Thanks a lot for the response. 


Actually it turned out to be quite simple and easy based on your mapping
file example. I was trying to play around the type attribute for the
holderObj field and hence was not able to make the stuff work. So as it
looks like, Castor automatically does an instance type check whenever it
comes across Object type and if the corresponding class instance mapping
is provided in the mapping file, it resolves it correctly.

Thanks a lot again. Appreciate your help.

Regards,
Sumanta



-----Original Message-----

From: Stephen Bash [mailto:[EMAIL PROTECTED] 
Sent: Monday, December 19, 2005 7:19 PM

To: [email protected]
Subject: Re: [castor-user] How to dynamic object resolution in Castor
XML mapping files

Sumanta-


This type of behavior is actually quite easy with Castor.  I used your 
Container class and created two dummy classes, ClassA and ClassB (one 
contains a string, the other a double).  I then wrote up a mapping file 
(see below), and a driver that creates two containers, puts them in an 
ArrayList, marshalls them out and unmarshalls them back in.


Here's the mapping file:

    <mapping>
      <class name="Container">
        <map-to xml="container"/>

        <field name="containerId" type="string">
          <bind-xml name="id" node="attribute" />
        </field>

        <field name="holderObj">
          <bind-xml name="child" />
        </field>
      </class>

      <class name="ClassA">
        <field name="str1" type="string" direct="true">
          <bind-xml name="string" node="attribute" />
        </field>
      </class>

      <class name="ClassB">
        <field name="dbl1" type="double" direct="true">
          <bind-xml name="pi" node="attribute" />
        </field>
      </class>
    </mapping>


Just a note, the class names need to be fully qualified (I cheated in 
this case).  And here's the output xml:


    <?xml version="1.0" encoding="UTF-8"?>
    <array-list xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";>
      <container id="Container1">
        <child string="Class A String" xsi:type="class-a"/>
      </container>
      <container id="Container2">
        <child pi="3.141592653589793" xsi:type="class-b"/>
      </container>
    </array-list>


Castor correctly unmarshalled the XML into objects with no problem.  If 
you want the xml to change based on the "contained" classes, you can 
look into the auto-naming attribute (bind-xml element) in the mapping 
documentation:


    http://castor.codehaus.org/xml-mapping.html

HTH,
Stephen

Sumanta Ranjan Das wrote:


Hi,

I have my object hierarchy that represents a container which in turn



can 


hold any type of other uder-defined objects. e.g. the following 
Container object looks like


public class Container {
 private String containerId ;
 private Object holderObj ;

 public String getContainerId()
 {
   return containerId ;
 }
 public void setContainerId(String id)
 {
   containerId  = id ;
 }
 public Object getHolderObj()
 {
   return holderObj ;
 }
 public void setHolderObj(Object obj)
 {
   holderObj = obj;
 }
}


I have 2 holder objects (A and B) which are altogether different in 
terms of relationship.


In one case when i create Container object, i could do
container.setHolderObj (A aObject)

whereas in other case, i would be doing
container.setHolderObj (B bObject)

In such a case how do i define the mapping file for Container class as




there is no explicit reference to either of A or B object in the 
Container class. All i know is that Container can contain either of A



or 


B during the runtime.


Does castor XML support such object structures? Can anyone share an 
example for the mapping file in case it's already supported?


Thanks and regards,
Sumanta



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