Question

Warning. This is a total newbie question for Groovy.. I’m from a Java background and I don’t want to do it that way, unless I must.

I’d like to create either a mapping that will traverse one object graph easily between another object graph.

Like:

customer.contact.address.identifier = incomingContact.location.address.idCode

Both of the above object structures are completely different, with sometimes different data types. In the above snippet, identifier is a Long, and idCode is a String. Also, some of the objects are null, so I want to create sturctures on the fly.

How can this be done better with groovy’s features of closures and more functional programming?

I was originally thinking inheritence or reflection solutions to minimize if/else conditions and instanceof based programming.

Any thoughts.

Here’s some pseudo code that I started which already has smells of java:

Method call:

customer.contact.address.identifier = convert(incomingContact.location.address.idCode)

And here’s the method:

Long convert(Object fromObject) {

    //example usage that were prototyping for this method (generically)    
    //fromObject = Long.valueOf(5);
    println "convert has: [" + fromObject + "]"
    if(fromObject != null) {

      return fromObject;
    }

    return null;
 }

The above snippet has complexity and problems in itself. For one, it errors out when I want to set back the calling structure a null object, but a “Long”.

The immediate error is:

groovy.lang.MissingMethodException: No signature of method: customer.contact.address.setIdentifier() is applicable for argument types: (null) values: [null]

My alternative thought is to use a mapping tool such as: http://dozer.sourceforge.net/ and allowing it to handle traversal of both graphs, but it’s java again, which I wanted that groovy dynamic type solution.

Answer 1

If you simply want to bind properties from one object to another, Groovy’s features won’t help you much. Something like Dozer might be worth a look.

BTW, here’s a Groovier way to write the code above:

Long convert(fromObject) {

  println "convert has: [" + fromObject + "]"
  fromObject as Long
}