问题描述
我尝试在 1.12.2 Forge 上制作一个 coremod，以修补 Lost Cities mod 中的一些缺失内容。 （来源：https://github.com/McJtyMods/LostCities/blob/1.12/src/main/java/mcjty/lostcities/dimensions/world/lost/BuildingInfo.java）
我和一个朋友写了这个 LostCitiesClasstransformer.java：（完整来源：https://github.com/Nick1st/LCPatches）
package seemdmax.lcpatches;
import static org.objectweb.asm.Opcodes.ALOAD;
import static org.objectweb.asm.Opcodes.IFGT;
import static org.objectweb.asm.Opcodes.IFLE;
import static org.objectweb.asm.Opcodes.IFNE;
import static org.objectweb.asm.Opcodes.ILOAD;
import static org.objectweb.asm.Opcodes.INVOKEINTERFACE;
import static org.objectweb.asm.Opcodes.INVOKESTATIC;
import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL;
import static org.objectweb.asm.Opcodes.GETFIELD;
import java.util.Arrays;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.Type;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.JumpInsnNode;
import org.objectweb.asm.tree.LabelNode;
import org.objectweb.asm.tree.LdcInsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;
import org.objectweb.asm.tree.VarInsnNode;
import mcjty.lostcities.api.ILostCityBuilding;
import net.minecraft.launchwrapper.IClasstransformer;
public class LostCitiesClasstransformer implements IClasstransformer {
private static final String[] classesBeingTransformed = { "mcjty.lostcities.dimensions.world.lost.BuildingInfo","mcjty.lostcities.dimensions.world.terraingen.LostCitiesTerrainGenerator"};
@Override
public byte[] transform(String name,String transformedname,byte[] classBeingTransformed) {
boolean isObfuscated = !name.equals(transformedname);
int index = Arrays.asList(classesBeingTransformed).indexOf(transformedname);
return index != -1 ? transform(index,classBeingTransformed,isObfuscated) : classBeingTransformed;
}
private static byte[] transform(int index,byte[] classBeingTransformed,boolean isObfuscated) {
System.out.println("Transform " + classesBeingTransformed[index] + " got called!");
try {
ClassNode classNode = new ClassNode();
ClassReader classReader = new ClassReader(classBeingTransformed);
classReader.accept(classNode,2);
System.out.println("Transforming " + classesBeingTransformed[index] + " Is Obf: " + isObfuscated);
switch (index) {
case 0:
transformlCCellars(classNode,isObfuscated);
break;
case 1:
transformBuildingBorders(classNode,isObfuscated);
break;
}
ClassWriter classWriter = new ClassWriter(ClassWriter.COmpuTE_MAXS /*| ClassWriter.COmpuTE_FRAMES*/);
classNode.accept(classWriter);
return classWriter.toByteArray();
} catch (Exception e) {
e.printstacktrace();
}
return classBeingTransformed;
}
private static void transformBuildingBorders(ClassNode terrainGenClass,boolean isObfuscated) {
final String METHOD = isObfuscated ? "generateBuilding" : "generateBuilding";
final String METHOD_DESC = isObfuscated
? "(Lmcjty/lostcities/dimensions/world/lost/BuildingInfo;Lmcjty/lostcities/dimensions/world/ChunkHeightmap;)V"
: "(Lmcjty/lostcities/dimensions/world/lost/BuildingInfo;Lmcjty/lostcities/dimensions/world/ChunkHeightmap;)V";
for (MethodNode method : terrainGenClass.methods) {
if (method.name.equals(METHOD) && method.desc.equals(METHOD_DESC)) {
System.out.println("Found method in BuildingInfo to transform");
AbstractInsnNode targetNode = null;
for (AbstractInsnNode instruction : method.instructions.toArray()) {
if (instruction.getopcode() == ALOAD) {
if (((VarInsnNode) instruction).var == 1 & instruction.getNext().getopcode() == GETFIELD & instruction.getNext().getNext().getopcode() == IFLE) {
System.out.println("Matched");
targetNode = instruction.getNext().getNext();
break;
}
}
}
if (targetNode != null) {
System.out.println("Target Node valid");
InsnList toInsert = new InsnList();
toInsert.add(new VarInsnNode(ALOAD,1));
toInsert.add(
new MethodInsnNode(INVOKEVIRTUAL,"mcjty/lostcities/dimensions/world/lost/BuildingInfo","floorsBelowGround","I",false));
toInsert.add(
new MethodInsnNode(INVOKEVIRTUAL,"seemdmax/lcpatches/Constants","getKey","()Ljava/lang/String;","java/lang/String","endsWith","(Ljava/lang/String;)Z",false));
toInsert.add(new JumpInsnNode(IFNE,((JumpInsnNode) targetNode).label));
method.instructions.insert(targetNode,toInsert);
System.out.println("Transform done!");
} else {
System.out.println("Something went wrong transforming LostCitiesTerrainGenerator!");
}
}
}
}
private static void transformlCCellars(ClassNode buildingInfoClass,boolean isObfuscated) {
//This is already working
}
}
我要打补丁的原代码（Bytecode Outline）：
L55
LINENUMBER 2338 L55
FRAME CHOP 3
ALOAD 1
GETFIELD mcjty/lostcities/dimensions/world/lost/BuildingInfo.floorsBelowGround : I
IFLE L68
包含我的更改的字节码大纲：
L55
LINENUMBER 2338 L55
FRAME CHOP 3
ALOAD 1
GETFIELD mcjty/lostcities/dimensions/world/lost/BuildingInfo.floorsBelowGround : I
IFLE L68
ALOAD 1
INVOKEVIRTUAL mcjty/lostcities/dimensions/world/lost/BuildingInfo.getBuildingType ()Ljava/lang/String;
LDC "#NOBORDER"
INVOKEVIRTUAL java/lang/String.endsWith (Ljava/lang/String;)Z
IFNE L68
我得到的堆栈跟踪：
java.lang.Stringindexoutofboundsexception: String index out of range: 1
at java.lang.String.charat(String.java:658)
at org.objectweb.asm.Type.getArgumentsAndReturnSizes(Type.java:420)
at org.objectweb.asm.MethodWriter.visitMethodInsn(MethodWriter.java:931)
at org.objectweb.asm.tree.MethodInsnNode.accept(MethodInsnNode.java:133)
at org.objectweb.asm.tree.InsnList.accept(InsnList.java:162)
at org.objectweb.asm.tree.MethodNode.accept(MethodNode.java:817)
at org.objectweb.asm.tree.MethodNode.accept(MethodNode.java:727)
at org.objectweb.asm.tree.ClassNode.accept(ClassNode.java:412)
at seemdmax.lcpatches.LostCitiesClasstransformer.transform(LostCitiesClasstransformer.java:59)
at seemdmax.lcpatches.LostCitiesClasstransformer.transform(LostCitiesClasstransformer.java:38)
at net.minecraftforge.fml.common.asm.ASMTransformerWrapper$TransformerWrapper.transform(ASMTransformerWrapper.java:256)
at net.minecraft.launchwrapper.LaunchClassLoader.runTransformers(LaunchClassLoader.java:279)
at net.minecraft.launchwrapper.LaunchClassLoader.findClass(LaunchClassLoader.java:176)
at java.lang.classLoader.loadClass(ClassLoader.java:418)
at java.lang.classLoader.loadClass(ClassLoader.java:351)
at mcjty.lostcities.dimensions.world.LostCityChunkGenerator.<init>(LostCityChunkGenerator.java:170)
at mcjty.lostcities.dimensions.world.LostWorldType.getChunkGenerator(LostWorldType.java:55)
at net.minecraft.world.WorldProvider.createChunkGenerator(WorldProvider.java:86)
at net.minecraft.world.WorldServer.createChunkProvider(WorldServer.java:890)
at net.minecraft.world.WorldServer.<init>(WorldServer.java:124)
at net.minecraft.server.integrated.IntegratedServer.loadAllWorlds(IntegratedServer.java:122)
at net.minecraft.server.integrated.IntegratedServer.init(IntegratedServer.java:160)
at net.minecraft.server.minecraftServer.run(minecraftServer.java:552)
at java.lang.Thread.run(Thread.java:748)
为什么我要对开源模组进行猴子补丁？ 我需要它作为一个模组包； Curseforge 不允许在 modpack 中修改 jar。 McJty 说，他不想要第二个 LC 项目，但他可以使用 coremods/mixin 等修补 LC。
任何帮助将不胜感激。如果您需要了解更多详情，请随时询问。提前致谢。
解决方法
问题来了：
toInsert.add(
new MethodInsnNode(INVOKEVIRTUAL,"mcjty/lostcities/dimensions/world/lost/BuildingInfo","floorsBelowGround","I",false));
您试图调用 floorsBelowGround 就像它是一个方法，但它实际上是一个字段。您需要使用 GETFIELD FieldInsnNode 而不是 INVOKEVIRTUAL MethodInsnNode。