The World Saved Data (WSD) system is an alternative to world capabilities that can attach data per world.
Each WSD implementation must subtype the
WorldSavedData class. There are three important methods to be aware of:
save: Allows the implementation to write NBT data to the world.
load: Allows the implementation to read previously saved NBT data.
setDirty: A method that must be called after changing the data, to notify the game that there are changes that need to be written. If not called,
#savewill not get called and the existing data will persist.
The constructor of the class also requires a
String. This is the name of the
.dat file stored within the
data folder for the implemented world. For example, if a WSD was named “example” within the Nether, then a file would be created at
WorldSavedData is loaded and/or attached to a world dynamically. As such, if one is never created on a world, then it will not exist.
WorldSavedDatas are created and loaded from the
DimensionSavedDataManager, which can be accessed by either
ServerWorld#getChunkSource. From there, you can get or create an instance of your WSD by calling
DimensionSavedDataManager#computeIfAbsent. This will attempt to get the current instance of the WSD if present or create a new one and load all available data.
To persist a WSD across worlds, a WSD should be attached to the Overworld dimension, which can be obtained from
MinecraftServer#overworld. The Overworld is the only dimension that is never fully unloaded and as such makes it perfect to store multi-world data on.