Minecraft 1.12.2 Forge Mod：以玩家身份发送消息

要在 Minecraft 1.12.2 Forge 中以安装该 Mod 的玩家身份发送消息，你可以使用下面的代码：

import net.minecraft.entity.player.EntityPlayer;
import net.minecraft.util.text.TextComponentString;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.event.FMLServerStartingEvent;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
import net.minecraftforge.fml.common.gameevent.PlayerEvent;

@Mod(modid = 'examplemod', name = 'Example Mod', version = '1.0')
public class ExampleMod {

    @Mod.EventHandler
    public void serverLoad(FMLServerStartingEvent event) {
        event.registerServerCommand(new SendMessageCommand());
    }

    public static class SendMessageCommand extends net.minecraft.command.CommandBase {

        @Override
        public String getName() {
            return 'sendmessage';
        }

        @Override
        public String getUsage(net.minecraft.command.ICommandSender sender) {
            return '/sendmessage <message>';
        }

        @Override
        public void execute(net.minecraft.command.ICommandSender sender, String[] args) {
            if (sender instanceof EntityPlayer) {
                EntityPlayer player = (EntityPlayer) sender;
                String message = String.join(' ', args);

                player.sendMessage(new TextComponentString(message));
            }
        }
    }

    @Mod.EventBusSubscriber
    public static class EventHandler {

        @SubscribeEvent
        public static void onPlayerLoggedIn(PlayerEvent.PlayerLoggedInEvent event) {
            if (event.player instanceof EntityPlayer) {
                EntityPlayer player = (EntityPlayer) event.player;
                player.sendMessage(new TextComponentString('Welcome to the server!'));
            }
        }
    }
}

这个 Mod 注册了一个名为 'sendmessage' 的命令，可以通过在游戏中输入 '/sendmessage ' 来发送消息。在玩家登录服务器时，也会发送一条欢迎消息给他们。

请注意，这只是一个简单的示例，你可以根据自己的需求进行修改和扩展。