设置药水效果Packet时ID104抛出异常致玩家被踢出

问题代码 #

PacketContainer hideplayer = new PacketContainer(PacketType.Play.Server.ENTITY_EFFECT);
hideplayer.getIntegers().write(0, player.getEntityId());
hideplayer.getBytes().write(0, (byte) 14);
hideplayer.getBytes().write(1, (byte) 1);
hideplayer.getIntegers().write(1, 1);

问题描述 #

在Bukkit环境使用ProtocolLib，按wiki.vg文档配置PacketContainer发送上述数据包时，玩家被踢出服务器，报错如下：

错误日志 #

[00:26:11 ERROR]: Packet encoding of packet ID 104 threw (skippable? false)
java.lang.IllegalArgumentException: Can't find id for 'null' in map Registry[ResourceKey[minecraft:root / minecraft:mob_effect] (Stable)]
        at net.minecraft.network.FriendlyByteBuf.writeId(FriendlyByteBuf.java:140) ~[?:?]
        at net.minecraft.network.protocol.game.ClientboundUpdateMobEffectPacket.write(ClientboundUpdateMobEffectPacket.java:58) ~[?:?]
        at net.minecraft.network.PacketEncoder.encode(PacketEncoder.java:41) ~[paper-1.19.3.jar:git-Paper-371]
        at net.minecraft.network.PacketEncoder.encode(PacketEncoder.java:14) ~[paper-1.19.3.jar:git-Paper-371]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:107) ~[netty-codec-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:717) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite(AbstractChannelHandlerContext.java:709) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:792) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:702) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.handler.codec.MessageToByteEncoder.write(MessageToByteEncoder.java:120) ~[netty-codec-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWrite0(AbstractChannelHandlerContext.java:717) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.invokeWriteAndFlush(AbstractChannelHandlerContext.java:764) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.write(AbstractChannelHandlerContext.java:790) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannelHandlerContext.writeAndFlush(AbstractChannelHandlerContext.java:758) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.DefaultChannelPipeline.writeAndFlush(DefaultChannelPipeline.java:1020) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.AbstractChannel.writeAndFlush(AbstractChannel.java:311) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at com.comphenix.protocol.injector.netty.channel.NettyChannelProxy.writeAndFlush(NettyChannelProxy.java:227) ~[ProtocolLib (1).jar:?]
        at com.comphenix.protocol.injector.netty.channel.NettyChannelProxy.writeAndFlush(NettyChannelProxy.java:233) ~[ProtocolLib (1).jar:?]
        at net.minecraft.network.Connection.doSendPacket(Connection.java:459) ~[?:?]
        at net.minecraft.network.Connection.lambda$sendPacket$11(Connection.java:433) ~[?:?]
        at com.comphenix.protocol.injector.netty.channel.NettyEventLoopProxy.lambda$proxyRunnable$2(NettyEventLoopProxy.java:48) ~[ProtocolLib (1).jar:?]
        at io.netty.util.concurrent.AbstractEventExecutor.runTask(AbstractEventExecutor.java:174) ~[netty-common-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:167) ~[netty-common-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:470) ~[netty-common-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:569) ~[netty-transport-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997) ~[netty-common-4.1.82.Final.jar:4.1.82.Final]
        at io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74) ~[netty-common-4.1.82.Final.jar:4.1.82.Final]
        at java.lang.Thread.run(Thread.java:833) ~[?:?]
[00:26:11 INFO]: LorkLork5487 lost connection: Internal Exception: io.netty.handler.codec.EncoderException: java.lang.IllegalArgumentException: Can't find id for 'null' in map Registry[ResourceKey[minecraft:root / minecraft:mob_effect] (Stable)]

原因分析 #

错误核心是Can't find id for 'null' in map Registry[minecraft:mob_effect]，说明数据包中的药水效果类型为null。1.19+版本中，ENTITY_EFFECT数据包（对应MC原生的ClientboundUpdateMobEffectPacket）不再支持直接用数字ID设置效果，需要传入完整的MobEffectInstance对象，旧版本手动写入字节/整数的方式会导致效果类型未正确初始化，出现null值。

修复代码 #

import org.bukkit.potion.MobEffect;
import org.bukkit.potion.MobEffectInstance;
import com.comphenix.protocol.PacketType;
import com.comphenix.protocol.ProtocolLibrary;
import com.comphenix.protocol.events.PacketContainer;

// 创建隐身效果数据包
PacketContainer hideplayer = new PacketContainer(PacketType.Play.Server.ENTITY_EFFECT);
// 设置目标玩家的实体ID
hideplayer.getIntegers().write(0, player.getEntityId());
// 创建隐身效果实例：持续1秒（20刻），等级0
MobEffectInstance invisibilityEffect = new MobEffectInstance(MobEffect.INVISIBILITY, 20, 0);
// 将效果实例写入数据包
hideplayer.getMobEffects().write(0, invisibilityEffect);

// 发送数据包
try {
    ProtocolLibrary.getProtocolManager().sendServerPacket(player, hideplayer);
} catch (Exception e) {
    e.printStackTrace();
}

说明 #

• 直接使用getMobEffects()方法写入MobEffectInstance对象，是ProtocolLib适配1.19+版本的正确方式，能避免版本兼容问题。
• 如果需要其他效果，替换MobEffect.INVISIBILITY为对应效果即可，比如MobEffect.SPEED。

内容的提问来源于stack exchange，提问作者EndermanPVP HK