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Saving Data per World [1.20.2] [SOLVED]


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Hello, I want to save an ArrayList of BlockPos for each world. I've seen this forge documentation but I don't really understand it. Additionally I think something has changed with 1.20.2. For example the computeIfAbsent method now takes different arguments such as a SavedData.Factory. Could someone please help me?


After a bit of try-and-error I got it. Here is the code if anyone is interested in it:

package de.chrisicrafter.loadit.utils;

import net.minecraft.core.BlockPos;
import net.minecraft.nbt.CompoundTag;
import net.minecraft.nbt.NbtUtils;
import net.minecraft.util.datafix.DataFixTypes;
import net.minecraft.world.level.saveddata.SavedData;

import java.util.ArrayList;

public class BeaconData extends SavedData {
    public final ArrayList<BlockPos> beaconPositions;

    public static SavedData.Factory<BeaconData> factory() {
        return new SavedData.Factory<>(BeaconData::new, BeaconData::load, DataFixTypes.LEVEL);

    public BeaconData() {
        beaconPositions = new ArrayList<>();

    public BeaconData(ArrayList<BlockPos> list) {
        beaconPositions = list;

    public CompoundTag save(CompoundTag tag) {
        //save to tag
        int size = beaconPositions.size();
        tag.putInt("size", size);
        for(int i = 0; i < size; i++) {
            tag.put("beacon_pos_" + i, NbtUtils.writeBlockPos(beaconPositions.get(i)));
        return tag;

    public static BeaconData load(CompoundTag tag) {
        ArrayList<BlockPos> list = new ArrayList<>();
        //load from tag
        int size = tag.getInt("size");
        for(int i = 0; i < size; i++) {
            list.add(NbtUtils.readBlockPos((CompoundTag) tag.get("beacon_pos_" + i)));
        return new BeaconData(list);

    public String toString() {
        StringBuilder builder = new StringBuilder();
        int size = beaconPositions.size();
        for(int i = 0; i < size; i++) {
            builder.append(" ");
        return builder.toString();


Edited by chrisicrafter27
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  • chrisicrafter27 changed the title to Saving Data per World [1.20.2] [SOLVED]

1. Pass the ServerLevel parameter into factory().

2. Call the getDataStorage() method within ServerLevel.

3. Call the computeIfAbsent() method within the ServerLevel::getDataStorage() method.

4. Pass the new SavedData.Factory<BeaconData>(BeaconData::new, BeaconData::load, DataFixTypes.LEVEL), yourmodID parameters into your computeIfAbsent() method.

5. Return it out as the factory() method.

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