FASTJSON2 Serializer for YACL

By
VesMaybeVesper

A config serializer for YetAnotherConfigLib using FASTJSON2

A serializer for YetAnotherConfigLib made using FASTJSON2.

FASTJSON2 Serializer for YACL (fastjson4yacl) is a library mod to allow other mods to use FastJSON2 for config (de)serialization. On its own it does nothing, you need other mods to utilize fastjson4yacl.

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Useage

Add as a dependancy as outlined on the version page*

// >= 1.21.11
    public static ConfigClassHandler<Config> HANDLER = ConfigClassHandler.createBuilder(Config.class)
            .id(Identifier.fromNamespaceAndPath(MOD_ID, "config"))
            .serializer(config -> FastJsonConfigSerializerBuilder.create(config)
                    .setPath(YACLPlatform.getConfigDir().resolve("modid.json"))
                    .build())
            .build();

// <= 1.21.10
    public static ConfigClassHandler<Config> HANDLER = ConfigClassHandler.createBuilder(Config.class)
            .id(ResourceLoccation.fromNamespaceAndPath(MOD_ID, "config"))
            .serializer(config -> FastJsonConfigSerializerBuilder.create(config)
                    .setPath(YACLPlatform.getConfigDir().resolve("modid.json"))
                    .build())
            .build();

JSON5

FastJSON2 doesn't offer any support for JSON5. If you need/want JSON5 for any reason, I would suggest continuing to use YACL's built-in Gson serializer. If you are migrating from a Json5 config back to a regular Json here is an example of how to auto migrate your user's configs from my mod Am I Up To Date?:

// Replace file & field names with your mod's

public class ConfigMigration {
    public static void migrate(){
        try {
            if (Files.exists(Path.of(YACLPlatform.getConfigDir() + "/aiutd.json5"))){
                AIUTD.LOG.info("Pre-2.5.0 config found. Migrating...!");

                String JSONContent = Files.readString(Path.of(YACLPlatform.getConfigDir() + "/aiutd.json5"));
                JSONObject oldConfig = JSON.parseObject(JSONContent, JSONReader.Feature.AllowUnQuotedFieldNames);

                Config.HANDLER.load();
                Config.menuAlert = Boolean.parseBoolean(oldConfig.getString("menuAlert"));
                Config.chatAlert = Boolean.parseBoolean(oldConfig.getString("chatAlert"));
                Config.multiLoaderBool = Boolean.parseBoolean(oldConfig.getString("multiLoaderBool"));
                Config.multiLoader = Config.LoaderEnum.valueOf(oldConfig.getString("multiLoader"));
                Config.localVersion = oldConfig.getString("localVersion");
                Config.modpackId = oldConfig.getString("versionAPI");
                Config.multiVersion = Boolean.parseBoolean(oldConfig.getString("multiVersion"));
                Config.useModpackName = Boolean.parseBoolean(oldConfig.getString("useModpackName"));
                Config.modpackName = oldConfig.getString("modpackName");
                Config.useCustomMessage = Boolean.parseBoolean(oldConfig.getString("useCustomMessage"));
                Config.customMessage = oldConfig.getString("customMessage");
                Config.linkChangelog = Boolean.parseBoolean(oldConfig.getString("linkChangelog"));
                Config.ignoreColor = Config.colorEnum.valueOf(oldConfig.getString("ignoreColor"));
                Config.messageColor = Config.colorEnum.valueOf(oldConfig.getString("messageColor"));
                Config.changelogColor = Config.colorEnum.valueOf(oldConfig.getString("changelogColor"));
                Config.HANDLER.save();
                AIUTD.LOG.info("Config migrated, please double check it for accuracy!");
                Files.deleteIfExists(Path.of(YACLPlatform.getConfigDir() + "/aiutd.json5"));
                AIUTD.LOG.info("Old config has been deleted");
            }
        } catch (IOException e) {
            AIUTD.LOG.error("Failed to migrate config! Please do so manually!", e);
        }

        try {
            if (Files.exists(Path.of(YACLPlatform.getConfigDir() + "/aiutd-enduser.json5"))){
                AIUTD.LOG.info("Pre-2.5.0 end user config found. Migrating...!");

                String JSONContent = Files.readString(Path.of(YACLPlatform.getConfigDir() + "/aiutd-enduser.json5"));
                JSONObject oldUserConfig = JSON.parseObject(JSONContent, JSONReader.Feature.AllowUnQuotedFieldNames);

                EndUserConfig.USERCONFIG.load();
                EndUserConfig.shouldIgnore = Boolean.parseBoolean(oldUserConfig.getString("shouldIgnore"));

                AIUTD.LOG.info("End user config migrated, please double check it for accuracy!");
                Files.deleteIfExists(Path.of(YACLPlatform.getConfigDir() + "/aiutd.json5"));
                AIUTD.LOG.info("Old end user config has been deleted");
            }
        } catch (IOException e) {
            AIUTD.LOG.error("Failed to migrate end user config! Please do so manually!", e);
        }
    }
}

FAQ

Is this faster than using the built-in Gson serializer?
- In a word, yes. In a few more words, based on pure library performance, yes. In practice it's a bit harder to say and will likely depend on the size of the config in question. Will it make a massive difference in anything when used in a single mod? Not noticeably; if you get several using it, you may start to see something a bit more tangible.
Why make it if it wont improve performance much?
- IDK, becuse I can? Free will and what not.
WAST has a better score on 3/4 of the tests, why not use it?†
- Becuse I am already familiar with FastJSON and didn't need to learn anything new to make it. If I need (or want) to learn WAST one day maybe I'll make something for it then.

*Until I set up another maven
†As of June 28th, 2026