[1.12.2]How to send command when player join a game?

[mlgmxyysd]

I use 

Minecraft.getMinecraft().player.sendChatMessage("/login " + password);

then game throw a NullPointerException.

Context:

package org.meowcat.autocommadner;
import net.minecraft.client.Minecraft;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
import net.minecraftforge.fml.common.gameevent.PlayerEvent;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;
import java.io.*;
import java.lang.reflect.Method;
import java.util.Properties;
public class JoinEvent {
	private Properties prop = new Properties();
	JoinEvent() {
		MinecraftForge.EVENT_BUS.register(this);
		FMLCommonHandler.instance().bus().register(this);
	}
	@SideOnly(Side.CLIENT)
	@SubscribeEvent
	public void PlayerJoinGame(PlayerEvent.PlayerLoggedInEvent event) throws IOException {
	    try{
	        Class mc = Class.forName(Minecraft.class.getName());
	        Method[] methods = mc.getMethods();
	        for (Method method : methods){
                Main.logger.info(method.getName());
            }
        } catch (ClassNotFoundException e ) {
            e.printStackTrace();
        }
		File file = new File("config/user.properties");
		if (!file.exists()) {
            Minecraft.getMinecraft().shutdown();
		}
        InputStream in = new BufferedInputStream(new FileInputStream("config/user.properties"));
        prop.load(in);
        String password = prop.getProperty("Password");
        String registered = prop.getProperty("IsRegistered");
        if (!registered.equals("true")) {
           Minecraft.getMinecraft().player.sendChatMessage("/register " + password + " " + password);
        } else {
           Minecraft.getMinecraft().player.sendChatMessage("/login " + password);
        }
	}
}

 

[Cadiboo]

What exactly are you trying to do? From an end-user persective

Edited December 27, 2018 by Cadiboo

[mlgmxyysd]

Auto send a command when player join game (server/single).

[mlgmxyysd]

  On 12/27/2018 at 3:23 PM, diesieben07 said:

Why are you making register / login commands? Mojang already has accounts, there is no need to make a secondary account system.

Expand  

That is not main issue.

I can replace by any command,it only is a placeholder.

[mlgmxyysd]

  On 12/27/2018 at 3:51 PM, diesieben07 said:

It might not be. Still, why? This usually means you are pirating the game.

 

You need to use ClientTickEvent, PlayedLoggedInEvent is server-side only. And that is not how @SideOnly works.

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The mod is a client mod,not a server mod.

[mlgmxyysd]

  On 12/27/2018 at 3:51 PM, diesieben07 said:

It might not be. Still, why? This usually means you are pirating the game.

 

You need to use ClientTickEvent, PlayedLoggedInEvent is server-side only. And that is not how @SideOnly works.

Expand  

No,I bought Minecraft.

[mlgmxyysd]

  On 12/28/2018 at 2:22 AM, diesieben07 said:

Yes, that is why you need ClientTickEvent.

Expand  

It not work.

When game inited(not join a game),force close by NullPointer.

[Cadiboo]

send your code and the error

[mlgmxyysd]

  On 12/28/2018 at 6:58 AM, Cadiboo said:

send your code and the error

Expand  

All code and error is posted at top.

[mlgmxyysd]

  On 12/29/2018 at 2:04 PM, diesieben07 said:

The code above has not changed. No error was posted.

Expand  

It may cause by network problem.

package org.meowcat.autocommadner;
import net.minecraft.client.Minecraft;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
import net.minecraftforge.fml.common.gameevent.TickEvent;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;
import java.io.*;
import java.lang.reflect.Method;
import java.util.Properties;
public class JoinEvent {
	private Properties prop = new Properties();
	JoinEvent() {
		MinecraftForge.EVENT_BUS.register(this);
		FMLCommonHandler.instance().bus().register(this);
	}
	@SideOnly(Side.CLIENT)
	@SubscribeEvent
	public void PlayerJoinGame(TickEvent.ClientTickEvent event) throws IOException {
	    try{
	        Class mc = Class.forName(Minecraft.class.getName());
	        Method[] methods = mc.getMethods();
	        for (Method method : methods){
                Main.logger.info(method.getName());
            }
        } catch (ClassNotFoundException e ) {
            e.printStackTrace();
        }
		File file = new File("config/user.properties");
		if (!file.exists()) {
            Minecraft.getMinecraft().shutdown();
		}
        InputStream in = new BufferedInputStream(new FileInputStream("config/user.properties"));
        prop.load(in);
        String password = prop.getProperty("Password");
        String registered = prop.getProperty("IsRegistered");
        if (!registered.equals("true")) {
           Minecraft.getMinecraft().player.sendChatMessage("/register " + password + " " + password);
        } else {
           Minecraft.getMinecraft().player.sendChatMessage("/login " + password);
        }
	}
}

java.lang.NullPointerException: Unexpected error
	at org.meowcat.autocommadner.JoinEvent.PlayerJoinGame(JoinEvent.java:42)
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler_18_JoinEvent_PlayerJoinGame_ClientTickEvent.invoke(.dynamic)
	at net.minecraftforge.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:90)
	at net.minecraftforge.fml.common.eventhandler.EventBus.post(EventBus.java:182)
	at net.minecraftforge.fml.common.FMLCommonHandler.onPreClientTick(FMLCommonHandler.java:344)
	at net.minecraft.client.Minecraft.func_71407_l(Minecraft.java:1708)
	at net.minecraft.client.Minecraft.func_71411_J(Minecraft.java:1098)
	at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:398)
	at net.minecraft.client.main.Main.main(SourceFile:123)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
	at java.lang.reflect.Method.invoke(Unknown Source)
	at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
	at net.minecraft.launchwrapper.Launch.main(Launch.java:28)

These are codes & errors

[Cadiboo]

What are you trying to do with that code?

Edited December 30, 2018 by Cadiboo

[mlgmxyysd]

  On 12/30/2018 at 7:49 PM, diesieben07 said:

Why on earth is this here? And blindly catching ClassNotFoundException and ignoring it is a bad idea. Handle exceptions properly.

 

Why on earth are you doing this every tick?! And registered should not be an option. Do not pirate the game.

 

You can only do this when the game is actually connected to a server. ClientTickEvent fires every client tick (duh), which is also during e.g. the main menu.

Expand  

Please don't get caught up in the secondary problem.

I only want to solve NullPointerException.

[mlgmxyysd]

  On 12/30/2018 at 1:14 PM, Cadiboo said:

What are you trying to do with that code?

Expand  

When player join a game (server/single), player will send a message(or command) automatically.

[mlgmxyysd]

  On 12/31/2018 at 1:32 AM, diesieben07 said:

Pirating the game is not a secondary problem.

Please clearly state why that isRegistered option is present. If not I will assume it is for enabling pirated "accounts", in which case you will receive a ban.

Expand  

A bukkit plugin named Authme.

[hiotewdew]

  On 12/27/2018 at 3:51 PM, diesieben07 said:

It might not be. Still, why? This usually means you are pirating the game.

 

You need to use ClientTickEvent, PlayedLoggedInEvent is server-side only. And that is not how @SideOnly works.

Expand  

Not to go too off topic, but /login can be used on servers as a staff security measure as well as for cracked server auth. So, it's not always malicious. I once had to use it on my online mode server because we had this hacker who somehow figured out that commands could be run by staff before they were authenticated (I have no idea how, but I'm not lying, he'd done it) and so I had to add a login command for staff to counteract it.

[mlgmxyysd]

  On 12/31/2018 at 3:20 PM, diesieben07 said:

I know, and this is the only reason this thread is not locked yet.

 

This explains nothing.

 

As far as the cause of your exception goes, I have already explained that above.

Expand  

OKAY, I does not use /login command, replace /login to /exp ok?

IS THIS OK?

package org.meowcat.autocommadner;
import net.minecraft.client.Minecraft;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;
import net.minecraftforge.fml.common.gameevent.TickEvent;
import net.minecraftforge.fml.relauncher.Side;
import net.minecraftforge.fml.relauncher.SideOnly;
import java.io.*;
import java.lang.reflect.Method;
import java.util.Properties;
public class JoinEvent {
	private Properties prop = new Properties();
	JoinEvent() {
		MinecraftForge.EVENT_BUS.register(this);
		FMLCommonHandler.instance().bus().register(this);
	}
	@SideOnly(Side.CLIENT)
	@SubscribeEvent
	public void PlayerJoinGame(TickEvent.ClientTickEvent event) throws IOException {
	    try{
	        Class mc = Class.forName(Minecraft.class.getName());
	        Method[] methods = mc.getMethods();
	        for (Method method : methods){
                Main.logger.info(method.getName());
            }
        } catch (ClassNotFoundException e ) {
            e.printStackTrace();
        }
            Minecraft.getMinecraft().player.sendChatMessage("/exp");
	}
}

[mlgmxyysd]

  On 12/31/2018 at 3:20 PM, diesieben07 said:

As far as the cause of your exception goes, I have already explained that above.

Expand  

And 

ClientTickEvent, PlayedLoggedInEvent

dont have sendChatMessage() method.

[mlgmxyysd]

  On 12/31/2018 at 6:24 AM, hiotewdew said:

Not to go too off topic, but /login can be used on servers as a staff security measure as well as for cracked server auth. So, it's not always malicious. I once had to use it on my online mode server because we had this hacker who somehow figured out that commands could be run by staff before they were authenticated (I have no idea how, but I'm not lying, he'd done it) and so I had to add a login command for staff to counteract it.

Expand  

Yes, it is necessary to use unofficial login system in offline-mode server.

[mlgmxyysd]

  On 1/16/2019 at 9:26 AM, diesieben07 said:

Don't make an offline-mode server.

Expand  

Why? I WANT to do that. Is that about you?

[mlgmxyysd]

 

  On 1/16/2019 at 9:26 AM, diesieben07 said:

Don't make an offline-mode server.

Expand  

If offline-mode server is not allowed, it is unable to set online-mode=false in server.prop.

[coalbricks]

  On 1/16/2019 at 1:34 PM, diesieben07 said:

Why do you want an offline-mode server?

There is no reason except:

1. To allow pirating the game, in which case that is not allowed.
2. For a local network, in which case there i no need for whitelisting (you are already in a local network, noone can join from outside).

 

Expand  

This is an old discussion, but after reading through it seems you've been unfair to @mlgmxyysd and wrong to assume that there are only two reasons why someone might want an offline mode server. I can give you a couple more valid and legitimate reasons:

1. The local network point is valid, and yes nobody can join from outside, but he could be running his server on a university network in which case custom authentication would be useful. It could be that nobody could join from outside, but 30 thousand people could join from inside.

2. He could be running his server on a network where Minecraft's authentication endpoint is blocked.

[Luis_ST]

1.12 is no longer supported on this forum.
Please update to a modern version of Minecraft to receive support.

Edited October 15, 2021 by Luis_ST