Re: [castor-user] Custom FieldHandler gives NullPointer in castor code

[Keith Visco]

Hi Jessica,

I haven't seen that problem before. Is it possible for you to send me a 
working (ie compilable and demonstrates the problem) test case which I 
can run locally?

--Keith

Jessica Perry Hekman wrote:
Hi all. I have a class which has a method (getCurrency()) which returns 
type java.util.Currency. The doc seems to suggest that writing a custom 
field handler is the way to proceed, and provides good instruction on how 
to do so. I created:

package com.ingenta.ics.api.rest.product;

import org.exolab.castor.mapping.GeneralizedFieldHandler;
import org.exolab.castor.mapping.FieldDescriptor;

import java.util.Currency;

/**
 * The FieldHandler for the Currency class
**/
public class CurrencyFieldHandler
    extends GeneralizedFieldHandler
{

    public CurrencyFieldHandler() {
        super();
    }

    public Object convertUponGet(Object value) {
        if (value == null) return null;
        Currency currency = (Currency)value;
        return currency.getCurrencyCode();
    }


    public Object convertUponSet(Object value) {
        return Currency.getInstance((String)value);
    }

    public Class getFieldType() {
        return Currency.class;
    }

    public Object newInstance( Object parent )
        throws IllegalStateException
    {
        //-- Since it's marked as a string...just return null,
        //-- it's not needed.
        return null;
    }

}

and in the XML:

<class name="com.ingenta.ics.ecommerce.api.item.Price">
   <map-to xml="price"/>
   <field name="id" type="com.ingenta.ics.item.Id" />
   <field name="amount" type="big-decimal"/>
   <field name="currency" type="string" 
          handler="com.ingenta.ics.api.rest.product.CurrencyFieldHandler"/>
</class>

Now, marshalling works beautifully. Unmarshalling gives me:

1) testProduct(com.ingenta.ics.api.item.ProductMarshallingTest)java.lang.NullPointerException at 
org.exolab.castor.xml.util.XMLFieldDescriptorImpl.hashCode(XMLFieldDescriptorImpl.java:416)
        at java.util.HashMap.hash(HashMap.java:261)
        at java.util.HashMap.containsKey(HashMap.java:339)

I am not sure what's going on -- was I supposed to implement hashCode? 
Castor's doc doesn't say so. Is this error familiar to anyone?

Thanks in advance,

Jessica


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