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Posted

What would be the easiest way of successfully modifying a vanilla method? I would like all calls coming to method A to be diverted to method B (which would be a custom method). If I could modify the method at runtime I would inject some code that just makes a call to method B, don't know if it works like that in reality. After searching online about this I've found out this is called reflection and that it's a very advanced procedure. However I've seen some mods around that have done exactly that, but I am having problems getting a grasp on how they did it. As always, any help would really be appreciated, thanks!

I still haven't published a mod because I can never get that in-dev version just right to warrant a public release. And yes, after two years of mod development I am still learning to speak Java.

 

Follow me on GitHub: https://github.com/yooksi

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Posted

What would be the easiest way of successfully modifying a vanilla method? I would like all calls coming to method A to be diverted to method B (which would be a custom method). If I could modify the method at runtime I would inject some code that just makes a call to method B, don't know if it works like that in reality. After searching online about this I've found out this is called reflection and that it's a very advanced procedure. However I've seen some mods around that have done exactly that, but I am having problems getting a grasp on how they did it. As always, any help would really be appreciated, thanks!

Modifying a vanilla method is not supported by forge or this forum as that requires editing base classes which is a coremod.

VANILLA MINECRAFT CLASSES ARE THE BEST RESOURCES WHEN MODDING

I will be posting 1.15.2 modding tutorials on this channel. If you want to be notified of it do the normal YouTube stuff like subscribing, ect.

Forge and vanilla BlockState generator.

Posted

I don't think he's asking how to edit the base code so to speak.

 

It would depend on which behaviours you intended to implement/"override" really. Using @SubscribeEvent and writing custom event handlers to "add" or "tweak" some existing Minecraft behaviour could give the illusion of overriding base methods, but is far simpler than trying to reflect the code.

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Posted

I would like all calls coming to method A to be diverted to method B...

*IF* method 'A' happens to have a Forge hook in it, then you can see what event it spawns and write an event handler (method 'B') whose result can cause the remainder of method 'A' to be skipped.

 

If not, then you probably can't get there from here.

 

Which method do you want to hijack?

The debugger is a powerful and necessary tool in any IDE, so learn how to use it. You'll be able to tell us more and get better help here if you investigate your runtime problems in the debugger before posting.

Posted

And why

Apparently I'm a complete and utter jerk and come to this forum just like to make fun of people, be confrontational, and make your personal life miserable.  If you think this is the case, JUST REPORT ME.  Otherwise you're just going to get reported when you reply to my posts and point it out, because odds are, I was trying to be nice.

 

Exception: If you do not understand Java, I WILL NOT HELP YOU and your thread will get locked.

 

DO NOT PM ME WITH PROBLEMS. No help will be given.

Posted

Modifying a vanilla method is not supported by forge or this forum as that requires editing base classes which is a coremod.

I do not wish to create a coremod, I would like to modify the content of the vanilla method during application runtime. There is a forum thread about a similar idea here, and it recommends using Access Transformers. Maybe what I am doing is considered creating a coremod, but this is not my intention.

 

There is no single way to achieve this. Modifying the actual code of vanilla classes is not possible as was said above.

Please describe what you want to achieve (describe the behavior, not how you intend to code it!).

I would like to replicate what the developer called atomicstrykers did here. He was able to redirect all calls coming from World.getRawLight to his own custom method, and like that was able to control all the light values in World. The reason I am interested in this is because I would like to create a moving light source that moves with the player, like an item torch emitting light when held for example. What makes me worry about this is the optimization side, so would the way he did it be a better approach then manually setting the light values and sending them to world for update?

I still haven't published a mod because I can never get that in-dev version just right to warrant a public release. And yes, after two years of mod development I am still learning to speak Java.

 

Follow me on GitHub: https://github.com/yooksi

Contact me on Twitter: https://twitter.com/yooksi

Read my Minecraft blog: https://yooksidoesminecraft.blogspot.de/

Posted

Modifying a vanilla method is not supported by forge or this forum as that requires editing base classes which is a coremod.

I do not wish to create a coremod, I would like to modify the content of the vanilla method during application runtime. There is a forum thread about a similar idea here, and it recommends using Access Transformers. Maybe what I am doing is considered creating a coremod, but this is not my intention.

 

Access Transformers are....

  • A coremod
  • Completely unnecessary as you can use Reflection
  • Don't modify code, only the access level (public, private, protected).

Apparently I'm a complete and utter jerk and come to this forum just like to make fun of people, be confrontational, and make your personal life miserable.  If you think this is the case, JUST REPORT ME.  Otherwise you're just going to get reported when you reply to my posts and point it out, because odds are, I was trying to be nice.

 

Exception: If you do not understand Java, I WILL NOT HELP YOU and your thread will get locked.

 

DO NOT PM ME WITH PROBLEMS. No help will be given.

Posted

I don't think an effect similar to DynamicLights is possible without a coremod at this time, so go ahead and investigate where exactly you need forge hooks inserted (as little as possible) and then submit a pull request. If the hooks make sense, it will go in.

Thanks for the advice, I will take a look at Forge's code and see where I could insert one.

 

Modifying a vanilla method is not supported by forge or this forum as that requires editing base classes which is a coremod.

I do not wish to create a coremod, I would like to modify the content of the vanilla method during application runtime. There is a forum thread about a similar idea here, and it recommends using Access Transformers. Maybe what I am doing is considered creating a coremod, but this is not my intention.

 

Access Transformers are....

  • A coremod
  • Completely unnecessary as you can use Reflection
  • Don't modify code, only the access level (public, private, protected).

Is it possible to do what I want to do with reflection then?

I still haven't published a mod because I can never get that in-dev version just right to warrant a public release. And yes, after two years of mod development I am still learning to speak Java.

 

Follow me on GitHub: https://github.com/yooksi

Contact me on Twitter: https://twitter.com/yooksi

Read my Minecraft blog: https://yooksidoesminecraft.blogspot.de/

Posted

Is it possible to do what I want to do with reflection then?

 

Unlikely.  But I don't know what it is you are trying to do.

Apparently I'm a complete and utter jerk and come to this forum just like to make fun of people, be confrontational, and make your personal life miserable.  If you think this is the case, JUST REPORT ME.  Otherwise you're just going to get reported when you reply to my posts and point it out, because odds are, I was trying to be nice.

 

Exception: If you do not understand Java, I WILL NOT HELP YOU and your thread will get locked.

 

DO NOT PM ME WITH PROBLEMS. No help will be given.

Posted

In some cases when method has no forge hooks, or other clear way of taking over calls, there is a an option that might* work if:

-Method is NOT static.

-Method is NOT private.

-Method is NOT final.

-Class is NOT final.

-You have / can gain access to classes' all instances.

 

When all of these (maybe not the * one, more about it in a second) are the case for you, you can create a class extending class that has the method and override it. Then what you have to do is replace all instances of class in question with your instance. It's easy if class is used as singleton, might be a bit harder if there are multiple instaces of it (but at that point, you always have a forge hook that allows accessing all/part of these instances).

Remember a few things though:

-Inner classes are not a problem, you'll just have to repeat process with its' external classes.

-If the instance(s) is/are stored in a private or final field, that's not a problem either. You have a way around both with reflection,

-If you have to default to vanilla(?) in overriden method, store instance that you replace and call it's method. It's very important, as other wise if other mods also use same replacement way...

 

*-If there are multiple mods using this way for the same thing, and one of them does not do it properly, it will break all other mods.

 

 

 

Also, just FYI, in case it will go to this point (like it did for me), using AOP (aspect oriented programming) java based language will not work (MC environment does not allow easy integration of such, if it is not integrated by forge).

Or at least, it did not work for me as much as i tried to hook in Aspect J (you CAN hook it with a coremod, but at this point, there's no point).

Posted

In some cases when method has no forge hooks, or other clear way of taking over calls, there is a an option that might* work if:

-Method is NOT static.

-Method is NOT private.

-Method is NOT final.

-Class is NOT final.

-You have / can gain access to classes' all instances.

 

When all of these (maybe not the * one, more about it in a second) are the case for you, you can create a class extending class that has the method and override it. Then what you have to do is replace all instances of class in question with your instance. It's easy if class is used as singleton, might be a bit harder if there are multiple instaces of it (but at that point, you always have a forge hook that allows accessing all/part of these instances).

Remember a few things though:

-Inner classes are not a problem, you'll just have to repeat process with its' external classes.

-If the instance(s) is/are stored in a private or final field, that's not a problem either. You have a way around both with reflection,

-If you have to default to vanilla(?) in overriden method, store instance that you replace and call it's method. It's very important, as other wise if other mods also use same replacement way...

 

*-If there are multiple mods using this way for the same thing, and one of them does not do it properly, it will break all other mods.

 

 

 

Also, just FYI, in case it will go to this point (like it did for me), using AOP (aspect oriented programming) java based language will not work (MC environment does not allow easy integration of such, if it is not integrated by forge).

Or at least, it did not work for me as much as i tried to hook in Aspect J (you CAN hook it with a coremod, but at this point, there's no point).

Replacing the instances is a difficult yet sometimes the only viable solution. Thanks for suggesting it.

I still haven't published a mod because I can never get that in-dev version just right to warrant a public release. And yes, after two years of mod development I am still learning to speak Java.

 

Follow me on GitHub: https://github.com/yooksi

Contact me on Twitter: https://twitter.com/yooksi

Read my Minecraft blog: https://yooksidoesminecraft.blogspot.de/

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    • Version 1.19 - Forge 41.0.63 I want to create a wolf entity that I can ride, so far it seems to be working, but the problem is that when I get on the wolf, I can’t control it. I then discovered that the issue is that the server doesn’t detect that I’m riding the wolf, so I’m struggling with synchronization. However, it seems to not be working properly. As I understand it, the server receives the packet but doesn’t register it correctly. I’m a bit new to Java, and I’ll try to provide all the relevant code and prints *The comments and prints are translated by chatgpt since they were originally in Spanish* Thank you very much in advance No player is mounted, or the passenger is not a player. No player is mounted, or the passenger is not a player. No player is mounted, or the passenger is not a player. No player is mounted, or the passenger is not a player. No player is mounted, or the passenger is not a player. MountableWolfEntity package com.vals.valscraft.entity; import com.vals.valscraft.network.MountSyncPacket; import com.vals.valscraft.network.NetworkHandler; import net.minecraft.client.Minecraft; import net.minecraft.network.syncher.EntityDataAccessor; import net.minecraft.network.syncher.EntityDataSerializers; import net.minecraft.network.syncher.SynchedEntityData; import net.minecraft.server.MinecraftServer; import net.minecraft.server.level.ServerPlayer; import net.minecraft.world.entity.EntityType; import net.minecraft.world.entity.Mob; import net.minecraft.world.entity.ai.attributes.AttributeSupplier; import net.minecraft.world.entity.ai.attributes.Attributes; import net.minecraft.world.entity.animal.Wolf; import net.minecraft.world.entity.player.Player; import net.minecraft.world.entity.Entity; import net.minecraft.world.InteractionHand; import net.minecraft.world.InteractionResult; import net.minecraft.world.item.ItemStack; import net.minecraft.world.item.Items; import net.minecraft.world.level.Level; import net.minecraft.world.phys.Vec3; import net.minecraftforge.event.TickEvent; import net.minecraftforge.eventbus.api.SubscribeEvent; import net.minecraftforge.network.PacketDistributor; public class MountableWolfEntity extends Wolf { private boolean hasSaddle; private static final EntityDataAccessor<Byte> DATA_ID_FLAGS = SynchedEntityData.defineId(MountableWolfEntity.class, EntityDataSerializers.BYTE); public MountableWolfEntity(EntityType<? extends Wolf> type, Level level) { super(type, level); this.hasSaddle = false; } @Override protected void defineSynchedData() { super.defineSynchedData(); this.entityData.define(DATA_ID_FLAGS, (byte)0); } public static AttributeSupplier.Builder createAttributes() { return Wolf.createAttributes() .add(Attributes.MAX_HEALTH, 20.0) .add(Attributes.MOVEMENT_SPEED, 0.3); } @Override public InteractionResult mobInteract(Player player, InteractionHand hand) { ItemStack itemstack = player.getItemInHand(hand); if (itemstack.getItem() == Items.SADDLE && !this.hasSaddle()) { if (!player.isCreative()) { itemstack.shrink(1); 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} this.flyingSpeed = this.getSpeed() * 0.1F; this.setSpeed((float) this.getAttributeValue(Attributes.MOVEMENT_SPEED) * 1.5F); this.setDeltaMovement(new Vec3(strafe, travelVector.y, forward).scale(this.getSpeed())); this.calculateEntityAnimation(this, false); } else { // The wolf does not have a passenger or the passenger is not a player System.out.println("No player is mounted, or the passenger is not a player."); super.travel(travelVector); } } public boolean hasSaddle() { return this.hasSaddle; } public void setSaddle(boolean hasSaddle) { this.hasSaddle = hasSaddle; } @Override protected void dropEquipment() { super.dropEquipment(); if (this.hasSaddle()) { this.spawnAtLocation(Items.SADDLE); this.setSaddle(false); } } @SubscribeEvent public static void onServerTick(TickEvent.ServerTickEvent event) { if (event.phase == TickEvent.Phase.START) { MinecraftServer server = net.minecraftforge.server.ServerLifecycleHooks.getCurrentServer(); if (server != null) { for (ServerPlayer player : server.getPlayerList().getPlayers()) { if (player.isPassenger() && player.getVehicle() instanceof MountableWolfEntity) { MountableWolfEntity wolf = (MountableWolfEntity) player.getVehicle(); 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import com.vals.valscraft.entity.MountableWolfEntity; import net.minecraft.network.FriendlyByteBuf; import net.minecraft.server.level.ServerLevel; import net.minecraft.server.level.ServerPlayer; import net.minecraft.world.entity.Entity; import net.minecraft.world.entity.player.Player; import net.minecraftforge.network.NetworkEvent; import java.util.function.Supplier; public class MountSyncPacket { private final boolean isMounted; public MountSyncPacket(boolean isMounted) { this.isMounted = isMounted; } public void encode(FriendlyByteBuf buffer) { buffer.writeBoolean(isMounted); } public static MountSyncPacket decode(FriendlyByteBuf buffer) { return new MountSyncPacket(buffer.readBoolean()); } public void handle(NetworkEvent.Context context) { context.enqueueWork(() -> { ServerPlayer player = context.getSender(); // Get the player from the context if (player != null) { // Verifies if the player has dismounted if (!isMounted) { Entity vehicle = player.getVehicle(); if (vehicle instanceof MountableWolfEntity wolf) { // Logic to remove the player as a passenger wolf.removePassenger(player); 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