Trying to serialize an object compactly using Castor

Question

I'm using Castor to write out a map of user ID's to time intervals. I'm using it to save and resume progress in a lengthy task, and I'm trying to make the XML as compact as possible. My map is from string userID's to a class that contains the interval timestamps, along with additional transient data that I don't need to serialize.

I'm able to use a nested class mapping:

...
<field name="userIntervals" collection="map">
 <bind-xml name="u">
  <class name="org.exolab.castor.mapping.MapItem">
   <field name="key" type="string"><bind-xml name="n" node="attribute"/></field>
   <field name="value" type="my.package.TimeInterval"/>
  </class>
 </bind-xml>
</field>
...
<class name="my.package.TimeInterval">
 <map-to xml="ti"/>
 <field name="intervalStart" type="long"><bind-xml name="s" node="attribute"/></field>
 <field name="intervalEnd" type="long"><bind-xml name="e" node="attribute"/></field>
</class>
...

And get output that looks like:

<u n="36164639"><value s="1292750896000" e="1292750896000"/></u>

What I'd like is the name, start, and end of the user in a single node like this.

<u n="36164639" s="1292750896000" e="1292750896000"/>

But I can't seem to finagle it so the start and end attributes in the "value" go in the same node as the "key". Any ideas would be greatly appreciated.

Answer 1

Am answering my own question here, since there is a solution that does exactly what I want, and there's actually an error in the explanation at http://www.castor.org/xml-mapping.html#Sample-3:-Using-the-container-attribute - the container attribute is exactly what's needed here.

Changing one line in the mapping:

<field name="value" type="my.package.TimeInterval" container="true"/>

did exactly what I wanted, it didn't create a subelement for the value, just mapped the fields into the existing parent element. Since then, I've used this quite a few times to map multiple-value classes into their parent.

The error of course is the documentation states you do this by setting the container attribute to false. Of course, it should be true.

Answer 2

Nash, I think to arrange the castor mapping is bit tricky. If you want to have structure like

<u n="36164639" s="1292750896000" e="1292750896000"/> 

Then you need to create a new pojo file where it will be having all the three fields Key,intervalStart,intervalEnd. And let the File name as KeyTimeInterval And map it like the below.

 <field name="userIntervals" collection="map">    
  <class name="org.exolab.castor.mapping.MapItem">   
    <field name="u" type="my.package.KeyTimeInterval">
      <bind-xml name="u" node="element"/>
    </field>             
   </class>        
 </field>



<class name="my.package.KeyTimeInterval">  
  <field name="key" type="String">
        <bind-xml name="n" node="attribute"/></field> 
    <field name="intervalStart" type="long">
        <bind-xml name="s" node="attribute"/></field>   
     <field name="intervalEnd" type="long">
      <bind-xml name="e" node="attribute"/></field>   
 </class> 

Answer 3

I think you should be able to use location on s and e. Try this:-

...

<class name="my.package.TimeInterval">
   <map-to xml="ti"/>
   <field name="intervalStart" type="long">
      <bind-xml name="s" location="u" node="attribute"/>
   </field>
   <field name="intervalEnd" type="long">
      <bind-xml name="e" location="u" node="attribute"/>
   </field>
</class>