You may choose between two approaches, as discussed in this similar Question, Serialization third-party classes with Simple XML (org.simpleframework.xml):
I do not know the pros and cons of each in comparison. But I do know how to implement the Transform approach. For that, read on.
Transform Approach
Three pieces are needed:
- An implementation of the Transform interface.
- An implementation of the Matcher interface.
- A RegistryMatcher instance where the Transform implementation is mapped to the data-type it handles.
All three of these are a part of the transform package.
I suggest putting your implementations in a "converters" package in your project.
Transform Implementation
Your Transform implementation may look like this.
This implementation here is a simplistic. It assumes you want the output to be the default ISO 8601 string generated by a DateTime’s toString method. And it assumes every text input will be compatible with the default parser in a DateTime constructor. To handle other formats, define a bunch of DateTimeFormatter instances, calling the parseDateTime method on each one in succession until a formatter succeeds without throwing an IllegalArgumentException. Another thing to consider is time zone; you may want to force the time zone to UTC or some such.
package com.your.package.converters.simplexml;
import org.joda.time.DateTime;
import org.simpleframework.xml.transform.Transform;
import org.slf4j.LoggerFactory;
/**
*
* © 2014 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for such usage and its consequences.
*/
public class JodaTimeDateTimeTransform implements Transform<DateTime>
{
//static final org.slf4j.Logger logger = LoggerFactory.getLogger( JodaTimeDateTimeTransform.class );
@Override
public DateTime read ( String input ) throws Exception
{
DateTime dateTime = null;
try {
dateTime = new DateTime( input ); // Keeping whatever offset is included. Not forcing to UTC.
} catch ( Exception e ) {
//logger.debug( "Joda-Time DateTime Transform failed. Exception: " + e );
}
return dateTime;
}
@Override
public String write ( DateTime dateTime ) throws Exception
{
String output = dateTime.toString(); // Keeping whatever offset is included. Not forcing to UTC.
return output;
}
}
Matcher Implementation
The Matcher implementation is quick and easy.
package com.your.package.converters.simplexml;
import org.simpleframework.xml.transform.Transform;
import org.simpleframework.xml.transform.Matcher;
/**
*
* © 2014 Basil Bourque. This source code may be used freely forever by anyone taking full responsibility for such usage and its consequences.
*/
public class JodaTimeDateTimeMatcher implements Matcher
{
@Override
public Transform match ( Class classType ) throws Exception
{
// Is DateTime a superclass (or same class) the classType?
if ( org.joda.time.DateTime.class.isAssignableFrom( classType ) ) {
return new JodaTimeDateTimeTransform();
}
return null;
}
}
Registry
Putting these into action means the use of a registry.
RegistryMatcher matchers = new RegistryMatcher();
matchers.bind( org.joda.time.DateTime.class , JodaTimeDateTimeTransform.class );
// You could add other data-type handlers, such as the "YearMonth" class in Joda-Time.
//matchers.bind( org.joda.time.YearMonth.class , JodaTimeYearMonthTransform.class );
Strategy strategy = new AnnotationStrategy();
Serializer serializer = new Persister( strategy , matchers );
And continue on the usual way with a serializer that understands the Joda-Time type(s).
