Java tutorial
/******************************************************************************* * Copyright 2015 Peter Cashel (pacas00@petercashel.net) * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. *******************************************************************************/ package net.petercashel.jmsDd.util; import java.util.ArrayList; import java.util.HashMap; import java.util.Iterator; import java.util.List; import java.util.Map; import net.petercashel.jmsDd.module.ModuleSystem; import org.objectweb.asm.AnnotationVisitor; import org.objectweb.asm.ClassReader; import org.objectweb.asm.ClassWriter; import org.objectweb.asm.Label; import org.objectweb.asm.MethodVisitor; import org.objectweb.asm.Opcodes; import org.objectweb.asm.Type; import org.objectweb.asm.tree.AbstractInsnNode; import org.objectweb.asm.tree.AnnotationNode; import org.objectweb.asm.tree.ClassNode; import org.objectweb.asm.tree.FieldNode; import org.objectweb.asm.tree.InsnList; import org.objectweb.asm.tree.InsnNode; import org.objectweb.asm.tree.LdcInsnNode; import org.objectweb.asm.tree.LocalVariableNode; import org.objectweb.asm.tree.MethodInsnNode; import org.objectweb.asm.tree.MethodNode; import org.objectweb.asm.tree.VarInsnNode; public class ASMTransformer { static List<ASMPlugin> plugins = new ArrayList<ASMPlugin>(); public final static boolean debug = false; public static void addASMPlugin(ASMPlugin plug) { plugins.add(plug); } public static byte[] transform(String name, byte[] bytes) { if (debug) System.out.println(bytes.length); ClassNode classNode = new ClassNode(); String classNameASM = name.replace('.', '/'); ClassReader classReader = new ClassReader(bytes); classReader.accept(classNode, 0); boolean DoModInit = false; boolean HasInit = false; String initDesc = "()V"; boolean lockDesc = false; try { try { for (int i = 0; i < classNode.visibleAnnotations.size(); i++) { AnnotationNode ann = (AnnotationNode) classNode.visibleAnnotations.get(i); if (ann.desc.equalsIgnoreCase("Lnet/petercashel/jmsDd/module/Module;")) { try { if (debug) System.out.println("ANNOTE!"); DoModInit = true; Map<String, Object> values = asmList2Map(ann.values); ModuleSystem.modulesToLoad.put( values.get("ModuleName").toString().replace("[", "").replace("]", ""), classNode.name.replace("/", ".")); } catch (Exception e) { e.printStackTrace(); } } } } catch (Exception e) { } try { if (DoModInit) { for (int i = 0; i < classNode.methods.size(); i++) { MethodNode m = (MethodNode) classNode.methods.get(i); if (m.name.contentEquals("<init>")) { initDesc = m.desc; if (m.desc.contentEquals("()V")) { HasInit = true; if (debug) System.out.println("Found <init>"); } } } } } catch (Exception e) { e.printStackTrace(); } } catch (Exception e) { e.printStackTrace(); } if (debug) System.out.println("Still alive?"); try { // L0 // LINENUMBER 43 L0 // ALOAD 0 // INVOKESPECIAL // CLASSNAME FOR ASM // ()V ////// This is effectically a super() call but to the discovered constructor // L1 // LINENUMBER 44 L1 // INVOKESTATIC net/petercashel/jmsDd/API/API$Impl.getAPI ()Lnet/petercashel/jmsDd/API/API; // ALOAD 0 // INVOKEINTERFACE net/petercashel/jmsDd/API/API.registerEventBus (Ljava/lang/Object;)V // L2 // LINENUMBER 46 L2 // RETURN // L3 // LOCALVARIABLE this // "L" + CLASSNAME FOR ASM + ";" // L0 L3 0 // LOCALVARIABLE e Lnet/petercashel/jmsDd/event/module/DummyEvent; L0 L3 1 // MAXSTACK = 2 // MAXLOCALS = 2 if (DoModInit) { if (HasInit) { if (debug) System.out.println("Adding Extra Constructor to " + name); MethodNode constructor = new MethodNode(Opcodes.ACC_PUBLIC, "<init>", "(Lnet/petercashel/jmsDd/event/module/DummyEvent;)V", null, null); Label L0 = new Label(); constructor.visitLabel(L0); constructor.visitVarInsn(Opcodes.ALOAD, 0); constructor.visitMethodInsn(Opcodes.INVOKESPECIAL, classNameASM, "<init>", initDesc); Label L1 = new Label(); constructor.visitLabel(L1); constructor.visitMethodInsn(Opcodes.INVOKESTATIC, "net/petercashel/jmsDd/API/API$Impl", "getAPI", "()Lnet/petercashel/jmsDd/API/API;"); constructor.visitVarInsn(Opcodes.ALOAD, 0); constructor.visitMethodInsn(Opcodes.INVOKEINTERFACE, "net/petercashel/jmsDd/API/API", "registerEventBus", "(Ljava/lang/Object;)V"); Label L2 = new Label(); constructor.visitLabel(L2); constructor.visitInsn(Opcodes.RETURN); Label L3 = new Label(); constructor.visitLabel(L3); constructor.visitLocalVariable("this", "L" + classNameASM + ";", null, L0, L3, 0); constructor.visitLocalVariable("e", "Lnet/petercashel/jmsDd/event/module/DummyEvent;", null, L0, L3, 1); constructor.visitMaxs(2, 2); constructor.visitEnd(); classNode.methods.add(constructor); } else { System.err.println("WARNING! " + name + " Doesn't have a default no-args constructor. Module loader cannot chain load the constructor. \n If you are recieving this error and your module has no constructors defined, or a no-args constructor defined, \n please report the bug to the author of JMSDd."); MethodNode constructor = new MethodNode(Opcodes.ACC_PUBLIC, "<init>", "(Lnet/petercashel/jmsDd/event/module/DummyEvent;)V", null, null); Label L0 = new Label(); constructor.visitLabel(L0); constructor.visitVarInsn(Opcodes.ALOAD, 0); //INVOKESPECIAL java/lang/Object.<init> ()V ////// There is no other constructor, call super() to Object. constructor.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V"); Label L1 = new Label(); constructor.visitLabel(L1); constructor.visitMethodInsn(Opcodes.INVOKESTATIC, "net/petercashel/jmsDd/API/API$Impl", "getAPI", "()Lnet/petercashel/jmsDd/API/API;"); constructor.visitVarInsn(Opcodes.ALOAD, 0); constructor.visitMethodInsn(Opcodes.INVOKEINTERFACE, "net/petercashel/jmsDd/API/API", "registerEventBus", "(Ljava/lang/Object;)V"); Label L2 = new Label(); constructor.visitLabel(L2); constructor.visitInsn(Opcodes.RETURN); Label L3 = new Label(); constructor.visitLabel(L3); constructor.visitLocalVariable("this", "L" + classNameASM + ";", null, L0, L3, 0); constructor.visitLocalVariable("e", "Lnet/petercashel/jmsDd/event/module/DummyEvent;", null, L0, L3, 1); constructor.visitMaxs(2, 2); constructor.visitEnd(); classNode.methods.add(constructor); } classNode.visitEnd(); ClassWriter wr = new ClassWriter(0); classNode.accept(wr); bytes = wr.toByteArray(); } } catch (Exception e) { e.printStackTrace(); } if (debug) System.out.println("Still alive."); if (debug) System.out.println(bytes.length); if (plugins.size() > 0) { for (ASMPlugin p : plugins) { try { bytes = p.transform(name, bytes); } catch (Exception e) { } } } return bytes; } private static Map<String, Object> asmList2Map(List list) { Map<String, Object> values = new HashMap(); for (int i = 0; i < list.size(); i += 2) { String name = (String) list.get(i); Object val = list.get(i + 1); values.put(name, val); } return values; } }