Java Reference
In-Depth Information
XML or SQLite
In the server configuration file, server/config/server.cfg , you can choose the back end that
the Database will use for loading and saving. By default, it uses an XML format file,
which will be saved in the server/db directory.
You can change that to use any of xml , mysql , or sqlite by editing this line in the server
config file:
For better performance, you can just change that option to sqlite without having to
do any additional configuration. To use the even higher performance mysql option,
you'd need to set it up using server/config/db.cfg and run a MySQL server.
Plugin: BackCmd with Save
Using the same ideas as with LocationSnapshot , you're going to add data storage
to the BackCmd plugin so that you can save the locations across server restarts.
I'll provide the outline and function signatures, but you will be writing the
bodies of the functions, the actual code to make it work. Buckle up!
Now, the BackCmd plugin is a little more complicated than our simple Location-
Snapshot . As you may remember from the plugin on page 128 , the BackCmd plugin
tracks more than just a location per player; it tracks a Stack of Location objects
for each player.
Bear in mind that the Database system can't actually store Location objects. It
can store a list, which we can use as a stack, but it can only store a list of a
single basic type. It cannot store a list of separate x-, y-, and z-coordinates,
or a list of arrays. So we're going to cheat a bit: we'll store the coordinates in
a string when we write, and pull them back out from a string into separate
doubles when we read.
Here's your to-do list for the code you're going to write:
•Create a SavedLocation , which will be a DataAccess object.
•The main plugin deals with players, and will want to just add a new Location
and retrieve the last location for a given player. So it makes sense to make
the SavedLocation look like a stack, with a pop and push method.
•Because SavedLocation will just look like a stack to the plugin, it will do the
database load and save functions internally (as private functions). You'll
need to write the private functions in SavedLocation that call the Database
and check for any exceptions.
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