I find that the standard way to access as list is via the query()
methods rather than any of the other approaches. The main difference between query
and the other methods is that you'll have to implement one of the callback interfaces (either RowMapper
, RowCallbackHandler
, or ResultSetExtractor
) to handle your result set.
A RowMapper
is likely what you'll find yourself using most of the time. It's used when each row of the result set corresponds to one object in your list. You only have to implement a single method mapRow
where you populate the type of object that goes in your row and return it. Spring also has a BeanPropertyRowMapper
which can populate the objects in a list via matching the bean property names to the column names (NB this class is for convenience not performance).
A RowCallbackHandler
is more useful when you need your results to be more than just a simple list. You'll have to manage the return object yourself you are using this approach. I usually find myself using this when I need a map structure as my return type (i.e. for grouped data for a tree table or if I'm creating a custom cache based of the primary key).
A ResultSetExtractor
is used when you want to control the iteration of the results. You implment a single method extractData
that will be the return value of the call to query
. I only find myself using this if I have to build some custom data structure that is more complex to build using either of the other callback interfaces.
The queryForList()
methods are valuable in that you don't have to implement these callback methods. There are two ways use queryForList. The first is if you're only querying a single column from the database (for example a list of strings) you can use the versions of the method that takes a Class as an argument to automatically give you a list of only objects of those classes.
When calling the other implementations of queryForList()
you'll get a list back with each entry being a map of for each column. While this is nice in that you are saved the expense of writing the callback methods, dealing with this data structure is quite unwieldy. You'll find yourself doing a lot of casting since the map's values are of type Object
.
I've actually never seen the queryForRowSet
methods used in the wild. This will load the entire result of the query into a CachedRowSet
object wapped by a Spring SqlRowSet. I see a big downside in using this object in that if you're passing the SqlRowSet
around to the other layers of your application, you're coupling those layers to your data access implementation.
You shouldn't see any huge performance differences between any of these calls except as I mentioned with the BeanPropertyRowMapper
. If you're working with some complex manipulation of a large result set, you might be able to get some performance gains from writing an optimized ResultSetExtractor
for your specific case.
If you want to learn more I would consult the Spring JDBC documentation and the JavaDoc for the classes I've mentioned. You can also take a look at some of the books on the Spring Framework. Though it's a bit dated Java Development with the Spring Framework has a very good section on working with the JDBC framework. Most of all, I would say just try writing some code with each method and see what works best for you.