Difference between findAll, getAll and list in Grails
With Grails there are several ways to do the same thing.
Finds all of domain class instances:
Book.findAll()
Book.getAll()
Book.list()
Retrieves an instance of the domain class for the specified id:
Book.findById(1)
Book.get(1)
When do you use each one? Are there significant differences in performance?
Answer
getAll is an enhanced version of get that takes multiple ids and returns a List of instances. The list size will be the same as the number of provided ids; any misses will result in a null at that slot. See http://grails.org/doc/latest/ref/Domain%20Classes/getAll.html
findAll lets you use HQL queries and supports pagination, but they're not limited to instances of the calling class so I use executeQuery instead. See http://grails.org/doc/latest/ref/Domain%20Classes/findAll.html
list finds all instances and supports pagination. See http://grails.org/doc/latest/ref/Domain%20Classes/list.html
get retrieves a single instance by id. It uses the instance cache, so multiple calls within the same Hibernate session will result in at most one database call (e.g. if the instance is in the 2nd-level cache and you've enabled it).
findById is a dynamic finder, like findByName, findByFoo, etc. As such it does not use the instance cache, but can be cached if you have query caching enabled (typically not a good idea). get should be preferred since its caching is a lot smarter; cached query results (even for a single instance like this) are pessimistically cleared more often than you would expect, but the instance cache doesn't need to be so pessimistic.
The one use case I would have for findById is as a security-related check, combined with another property. For example instead of retrieving a CreditCard instance using CreditCard.get(cardId), I'd find the currently logged-in user and use CreditCard.findByIdAndUser(cardId, user). This assumes that CreditCard has a User user property. That way both properties have to match, and this would block a hacker from accessing the card instance since the card id might match, but the user wouldn't.