Java tutorial
package org.coldswap.util; /** * (C) Copyright 2013 Faur Ioan-Aurel. * <p/> * All rights reserved. This program and the accompanying materials * are made available under the terms of the GNU Lesser General Public License * (LGPL) version 2.1 which accompanies this distribution, and is available at * http://www.gnu.org/licenses/lgpl-2.1.html * <p/> * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * <p/> * Contributors: * faur * <p/> * Created at: * 8:39 PM 5/14/13 */ import org.objectweb.asm.Opcodes; import org.objectweb.asm.Type; import org.objectweb.asm.tree.*; /** * Helper class for extracting method return type, method params type, etc... */ public class MethodUtil { public static Type getReturnType(MethodNode methodNode) { String methodDesc = methodNode.desc; // get 2 strings one containing the var params and // the other the return type String[] descs = methodDesc.split("\\)"); return Type.getReturnType(descs[1]); } public static Type[] getParamsType(MethodNode methodNode) { String methodDesc = methodNode.desc; // get 2 strings one containing the var params and // the other the return type String[] descs = methodDesc.split("\\)"); // get a list of params that this method has String[] paramType = null; if (!descs[0].equals("(")) { paramType = descs[0].substring(1).split(";"); // append ";" if param is not primitive type for (int i = 0; i < paramType.length; i++) { if (paramType[i].length() > 1) { paramType[i] = paramType[i] + ";"; } } } Type[] toRet = new Type[0]; if (paramType != null) { toRet = new Type[paramType.length]; for (int i = 0; i < toRet.length; i++) { toRet[i] = Type.getType(paramType[i]); } } return toRet; } public static Type classToType(Class<?> aClass) { return Type.getType(aClass); } public static Type[] classToType(Class<?>[] classes) { Type[] toRet = new Type[classes.length]; for (int i = 0; i < toRet.length; i++) { toRet[i] = classToType(classes[i]); } return toRet; } public static MethodNode createObjectHelperMethod(String className, int counter) { int acc = Opcodes.ACC_PUBLIC; String methodName = TransformerNameGenerator.getObjectMethodNameWithCounter(className, counter); MethodNode mn = new MethodNode(acc, methodName, "([Ljava/lang/Object;)Ljava/lang/Object;", null, null); InsnList insnList = mn.instructions; LabelNode l0 = new LabelNode(); insnList.add(l0); insnList.add(new InsnNode(Opcodes.ACONST_NULL)); insnList.add(new InsnNode(Opcodes.ARETURN)); LabelNode l1 = new LabelNode(); insnList.add(l1); String classLiteral = "L" + className + ";"; mn.localVariables.add(new LocalVariableNode("this", classLiteral, null, l0, l1, 0)); mn.localVariables.add(new LocalVariableNode("args", "[Ljava/lang/Object;", null, l0, l1, 1)); mn.maxStack = 1; mn.maxLocals = 2; return mn; } public static MethodNode createIntHelperMethod(String className, int counter) { int acc = Opcodes.ACC_PUBLIC; String methodName = TransformerNameGenerator.getIntMethodNameWithCounter(className, counter); MethodNode mn = new MethodNode(acc, methodName, "(I)Ljava/lang/Object;", null, null); InsnList insnList = mn.instructions; LabelNode l0 = new LabelNode(); insnList.add(l0); insnList.add(new InsnNode(Opcodes.ACONST_NULL)); insnList.add(new InsnNode(Opcodes.ARETURN)); LabelNode l1 = new LabelNode(); insnList.add(l1); String classLiteral = "L" + className + ";"; mn.localVariables.add(new LocalVariableNode("this", classLiteral, null, l0, l1, 0)); mn.localVariables.add(new LocalVariableNode("arg", "I", null, l0, l1, 1)); mn.maxStack = 1; mn.maxLocals = 2; return mn; } public static MethodNode createLongHelperMethod(String className, int counter) { int acc = Opcodes.ACC_PUBLIC; String methodName = TransformerNameGenerator.getLongMethodNameWithCounter(className, counter); MethodNode mn = new MethodNode(acc, methodName, "(J)Ljava/lang/Object;", null, null); InsnList insnList = mn.instructions; LabelNode l0 = new LabelNode(); insnList.add(l0); insnList.add(new InsnNode(Opcodes.ACONST_NULL)); insnList.add(new InsnNode(Opcodes.ARETURN)); LabelNode l1 = new LabelNode(); insnList.add(l1); String classLiteral = "L" + className + ";"; mn.localVariables.add(new LocalVariableNode("this", classLiteral, null, l0, l1, 0)); mn.localVariables.add(new LocalVariableNode("arg", "J", null, l0, l1, 1)); mn.maxStack = 1; mn.maxLocals = 3; return mn; } public static MethodNode createFloatHelperMethod(String className, int counter) { int acc = Opcodes.ACC_PUBLIC; String methodName = TransformerNameGenerator.getFloatMethodNameWithCounter(className, counter); MethodNode mn = new MethodNode(acc, methodName, "(F)Ljava/lang/Object;", null, null); InsnList insnList = mn.instructions; LabelNode l0 = new LabelNode(); insnList.add(l0); insnList.add(new InsnNode(Opcodes.ACONST_NULL)); insnList.add(new InsnNode(Opcodes.ARETURN)); LabelNode l1 = new LabelNode(); insnList.add(l1); String classLiteral = "L" + className + ";"; mn.localVariables.add(new LocalVariableNode("this", classLiteral, null, l0, l1, 0)); mn.localVariables.add(new LocalVariableNode("arg", "F", null, l0, l1, 1)); mn.maxStack = 1; mn.maxLocals = 2; return mn; } public static MethodNode createStringHelperMethod(String className, int counter) { int acc = Opcodes.ACC_PUBLIC; String methodName = TransformerNameGenerator.getStringMethodNameWithCounter(className, counter); MethodNode mn = new MethodNode(acc, methodName, "(Ljava/lang/String;)Ljava/lang/Object;", null, null); InsnList insnList = mn.instructions; LabelNode l0 = new LabelNode(); insnList.add(l0); insnList.add(new InsnNode(Opcodes.ACONST_NULL)); insnList.add(new InsnNode(Opcodes.ARETURN)); LabelNode l1 = new LabelNode(); insnList.add(l1); String classLiteral = "L" + className + ";"; mn.localVariables.add(new LocalVariableNode("this", classLiteral, null, l0, l1, 0)); mn.localVariables.add(new LocalVariableNode("arg", "Ljava/lang/String;", null, l0, l1, 1)); mn.maxStack = 1; mn.maxLocals = 2; return mn; } public static int getRetOpcodeToReplace(Type retType) { String retDesc = retType.getDescriptor(); int opcode = Opcodes.IRETURN; if ("Z".equals(retDesc)) { opcode = Opcodes.IRETURN; } else if ("B".equals(retDesc)) { opcode = Opcodes.IRETURN; } else if ("C".equals(retDesc)) { opcode = Opcodes.IRETURN; } else if ("S".equals(retDesc)) { opcode = Opcodes.IRETURN; } else if ("I".equals(retDesc)) { opcode = Opcodes.IRETURN; } else if ("J".equals(retDesc)) { opcode = Opcodes.LRETURN; } else if ("F".equals(retDesc)) { opcode = Opcodes.FRETURN; } else if ("D".equals(retDesc)) { opcode = Opcodes.DRETURN; } return opcode; } }