Reverse geocoding & POIs without ArcGIS

Hello all,
I've created a GIS application based on ArcGIS (C#/.NET) that reads a
set of shapefiles containing POIs (points of interest), and displays
them on a map. More importantly, given a random lat/long, the
application uses ArcMap to reverse geocode the lat/long and retrieve
the nearest points of interest.

So far so good.

However, I'm moving away from both C# and ArcGIS, and moving into an
open source, Java platform.

Does anyone know how to do this is Java? I don't want to use ArcGIS's
Java APIs (I don't want to use ArcGIS at all).

Here's what I'm thinking:
a. If I find an open source Java library that allows me to efficiently
read shapefiles, read POIs in them and retrieve a list of the nearest
POIs given a lat/long, that would be great, or
b. I manually convert/store the POIs in the shapefiles into a spatial
database such as Oracle, SQL server 2008, POstgreSQL, etc., and then
use spatial queries to read POIs in the database and retrieve a list
of the nearest POIs given a lat/long.

Options, opinions, anyone?
Thanks in advance.