我设法弄清楚了.您需要使用您自己的插件覆盖Morphia的ClassLoader.如果有人使用Spigot或Bukkit寻找答案:

I've managed to figure it out. You need to override Morphia's ClassLoader with your plugin's own. In case anyone using Spigot or Bukkit are looking for the answer:

morphia.getMapper().getOptions().setObjectFactory(new DefaultCreator() {
    @Override
    protected ClassLoader getClassLoaderForClass() {
        return JavaPlugin.getClassLoader();
    }
});