Re: [castor-dev] XML mapping problem

[Pezzotti Damiano]

Thanks. It works!

When wrappers elements will be supported?


Damiano Pezzotti 
........................................
Software Architect | Alambitco
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-----Messaggio originale-----
Da: Keith Visco [mailto:[EMAIL PROTECTED]] 
Inviato: gioved� 11 aprile 2002 21.56
A: [EMAIL PROTECTED]
Oggetto: Re: [castor-dev] XML mapping problem




> Pezzotti Damiano wrote:
> 
> Hi,
> I have a problem.
> 
> I have this XML code :
> 
> <PAGE>
>     <DAY>
>         <NUMBER>05</NUMBER>
>         <DATE>2002-03-17</DATE>
>     <DAY>
> ......
> 
> 
> 
> I have the object Page that has 2 fields , number and date, but I 
> haven't the ogject Day.
> 
> How can I write the mapping file?
> 
> <mapping>
>    <class name="Page">
>       <map-to xml="PAGE"/>
> 
>       <field name="date" type="java.lang.String">
>          <bind-xml name="??????" />
>       </field>
> 
>       <field name="number" type="java.lang.String">
>          <bind-xml name="???" />
>       </field>
> 

Currently, "wrapper elements" are not supported. So you'll need to do
some extra work to get it working.

1. You can use XSLT to remove (unwrap) the <DAY> element.

2. -Or- you can create a Day object for your object model.

3. -Or- you can use a special FieldHandler so that the Day object is not
needed
   for your object model, only for unmarshalling and marshalling.


I think number 3 is the best approach because it doesn't require
altering your XML or your object model.

To use number 3...

1. create a Day object (only used for marshalling/unmarshalling, 
   not part of the object model)

2. create a FieldHandler as such:

---

import org.exolab.castor.mapping.FieldHandler;
import org.exolab.castor.mapping.ValidityException;

/** 
 * The FieldHandler for the "day wrapper" field of the Page class. **/
public class DayHandler 
    implements org.exolab.castor.mapping.FieldHandler 
{
   
   /**
    * Creates a new DayHandler for the Page class
   **/
   public DayHandler() {
    super();
   } 
   
    /**
     * Returns the value of the field from the object.
     *
     * @param object The object
     * @return The value of the field
     * @throws IllegalStateException The Java object has changed and
     *  is no longer supported by this handler, or the handler is not
     *  compatiable with the Java object
     */
    public Object getValue( Object object ) 
        throws IllegalStateException 
    {
        Page page = (Page)object;
        Day  day  = new Day();
        day.setDate(page.getDate());
        day.setNumber(page.getNumber());
        return day;
    }
    

    /**
     * Sets the value of the field on the object.
     *
     * @param object The object
     * @param value The new value
     * @throws IllegalStateException The Java object has changed and
     *  is no longer supported by this handler, or the handler is not
     *  compatiable with the Java object
     * @thorws IllegalArgumentException The value passed is not of
     *  a supported type
     */
    public void setValue( Object object, Object value )
        throws IllegalStateException, IllegalArgumentException
    {
        Page page = (Page)object;
        Day  day  = (Day)value;
        page.setDate(day.getDate());
        page.setNumber(day.getNumber());
    }


    /**
     * Sets the value of the field to a default value.
     * <p>
     * Reference fields are set to null, primitive fields are set to
     * their default value, collection fields are emptied of all
     * elements.
     *
     * @param object The object
     * @throws IllegalStateException The Java object has changed and
     *  is no longer supported by this handler, or the handler is not
     *  compatiable with the Java object
     */
    public void resetValue( Object object )
        throws IllegalStateException, IllegalArgumentException
    {
        //-- add reset code here
    }


    /**
     * @deprecated No longer supported
     */
    public void checkValidity( Object object )
        throws ValidityException, IllegalStateException 
    {
        //-- add validation check if desired
    }


    /**
     * Creates a new instance of the object described by this field.
     *
     * @param parent The object for which the field is created
     * @return A new instance of the field's value
     * @throws IllegalStateException This field is a simple type and
     *  cannot be instantiated
     */
    public Object newInstance( Object parent )
        throws IllegalStateException
    {
        return new Day();
    }
    
}

---

3. modify your mapping as such:

 <mapping>
    <class name="Page">
       <map-to xml="PAGE"/>
       <field name="day" type="Day" handler="DayHandler">
          <bind-xml name="DAY"/>
       </field>
    </class>
 </mapping> 


Hope that helps,

--Keith

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