Colin Harrington

Rather than implement properties in the Java Language, we have a convention called a Java Bean.  This basically means that properties are implemented with getter and setter methods with a PascalCase property name in the method among a few other simple conventions. 

Grails makes it incredibly easy to manage domain classes since it is inherently domain-centric.  When you need to enhance your Domain classes at the core of your application, you have an option of implementing your own getters and setters.   I love that by default you do not have to implement your own setters, but you have the power to do so if you wish;  the principle of sensible defaults.  Here is an example of a Book Object with two properties, author and isbn.

class Book {
    String author
    String isbn
}

Consider the case where a Book is in your Database with the ISBN of 978-1430219262 and a user tries to search for "9781430219262".  Unless you do some searchable magic, the user will not find the book.  A simple solution fo the issue would be to never store ‘-’ in the databse.  to make this happen you could easily remove the dash in the setter.  So your domain would look like this:

class Book {
    String author
    String isbn

    void setIsbn(String i) {
        isbn = i.replace('-','')
    }
}

When I first tried this, I failed a few times before I got it right.  Maybe I was just spoiled with Groovy’s groovyness, but I started out writing
def setIsbn(i){ ... }  and when that didn’t work: void setIsbn(i){ ... } which was being called, but never actually set the property.  Then I had a forehead smacking moment where I realized that the method signature must precisely match the signature of a JavaBean setter like public void setPropertyName(Type propVal) { ... }  In my case I had to make sure that the method was public (public by default), has a return type of void (which is not the default behavior of a closure), and the parameter passed in was of the same type as the property (String)

And then I blogged about it — the fourth day.