Caching database results in Java objects under Play 2.1

Question

In the model layer of an application I'm working on, I have an Organization class, that has a one-to-many relationship with a Person class. Person objects can have a number of different roles, based on their one-to-many relationships to another set of objects of the superclass Certificate . To determine if a Person is a "signatory", I call

public boolean isSignatory() {
    return this.certificatesAsSignatory.size() > 0;
}

I want to return a list of signatories for an organization, so I'm going to loop through the set of related persons, checking for signatories. What I'd like to do is cache the result, so I don't have to regenerate the data from the database each time. I've added a private field to Organization that looks like

private List<Person> signatories;

and the basic method looks like this

public List<Person> getSignatories() {
    for ( final Person person : this.people ) {
        if ( person.isSignatory() ) {
            this.signatories.add( person );
        }
    }
    return this.signatories;
}

Now, when I call the method to return the list, I'll store the result in signatories and return it. When it's called again, I can check if signatories already contains a list, and return that instead of doing the calculations again.

My question is this: how do I keep the cache of the list of signatories up to date?

Answer 1

So the list contains all persons who are signatories. It would seem a good idea to update that list every time Person changes from being a signatory to not being one, or vice versa. Im guessing you have some method that sets if a Person is a signatory or not? In that function you could make a call to clear the cache so it would refill the list next time it is needed. Im also guessing it can be done when a new Person is inserted into the db and should be a signatory.

Its hard to be more specific since I dont know how your code is sturctured. But the idea of a cache is to reset it when the data thats in it changes.