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javassist和asm都是动态创建、修改字节码的类库。个人感觉主要区别是：asm的性能要好一些。javassist的主要优势是学习成本 低，可以根据java源代码生成字节码，而不必直接和字节码打交道。（本例不涉及生成字节码的部分）发现javassist貌似不支持泛型。

基于javassist的实现

package org.cc.tx.aop.javassit;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.Modifier;
import javassist.NotFoundException;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.LocalVariableAttribute;
import javassist.bytecode.MethodInfo;import org.cc.core.CcException;
import org.cc.core.common.Exceptions;/*** <p>* <font color="red">依赖javassit</font>的工具类，获取方法的参数名* </p>* * @author dixingxing* @date Apr 20, 2012*/
public class Classes {private Classes() {}/*** * <p>* 获取方法参数名称* </p>* * @param cm* @return*/protected static String[] getMethodParamNames(CtMethod cm) {CtClass cc = cm.getDeclaringClass();MethodInfo methodInfo = cm.getMethodInfo();CodeAttribute codeAttribute = methodInfo.getCodeAttribute();LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);if (attr == null) {throw new CcException(cc.getName());}String[] paramNames = null;try {paramNames = new String[cm.getParameterTypes().length];} catch (NotFoundException e) {Exceptions.uncheck(e);}int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;for (int i = 0; i < paramNames.length; i++) {paramNames[i] = attr.variableName(i + pos);}return paramNames;}/*** 获取方法参数名称，按给定的参数类型匹配方法* * @param clazz* @param method* @param paramTypes* @return*/public static String[] getMethodParamNames(Class<?> clazz, String method,Class<?>... paramTypes) {ClassPool pool = ClassPool.getDefault();CtClass cc = null;CtMethod cm = null;try {cc = pool.get(clazz.getName());String[] paramTypeNames = new String[paramTypes.length];for (int i = 0; i < paramTypes.length; i++)paramTypeNames[i] = paramTypes[i].getName();cm = cc.getDeclaredMethod(method, pool.get(paramTypeNames));} catch (NotFoundException e) {Exceptions.uncheck(e);}return getMethodParamNames(cm);}/*** 获取方法参数名称，匹配同名的某一个方法* * @param clazz* @param method* @return* @throws NotFoundException*             如果类或者方法不存在* @throws MissingLVException*             如果最终编译的class文件不包含局部变量表信息*/public static String[] getMethodParamNames(Class<?> clazz, String method) {ClassPool pool = ClassPool.getDefault();CtClass cc;CtMethod cm = null;try {cc = pool.get(clazz.getName());cm = cc.getDeclaredMethod(method);} catch (NotFoundException e) {Exceptions.uncheck(e);}return getMethodParamNames(cm);}}

基于asm的实现

/*** Classes.java 9:22:44 AM Apr 23, 2012** Copyright(c) 2000-2012 HC360.COM, All Rights Reserved.*/
package org.cc.core.common;import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;import org.cc.core.asm.ClassReader;
import org.cc.core.asm.ClassVisitor;
import org.cc.core.asm.ClassWriter;
import org.cc.core.asm.Label;
import org.cc.core.asm.MethodVisitor;
import org.cc.core.asm.Opcodes;
import org.cc.core.asm.Type;/*** <p>* 基于asm的工具类* </p>* * @author dixingxing* @date Apr 23, 2012*/
public final class Classes {private Classes() {}/*** * <p>比较参数类型是否一致</p>** @param types asm的类型({@link Type})* @param clazzes java 类型({@link Class})* @return*/private static boolean sameType(Type[] types, Class<?>[] clazzes) {// 个数不同if (types.length != clazzes.length) {return false;}for (int i = 0; i < types.length; i++) {if(!Type.getType(clazzes[i]).equals(types[i])) {return false;}}return true;}/*** * <p>获取方法的参数名</p>** @param m* @return*/public static String[] getMethodParamNames(final Method m) {final String[] paramNames = new String[m.getParameterTypes().length];final String n = m.getDeclaringClass().getName();final ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);ClassReader cr = null;try {cr = new ClassReader(n);} catch (IOException e) {e.printStackTrace();Exceptions.uncheck(e);}cr.accept(new ClassVisitor(Opcodes.ASM4, cw) {@Overridepublic MethodVisitor visitMethod(final int access,final String name, final String desc,final String signature, final String[] exceptions) {final Type[] args = Type.getArgumentTypes(desc);// 方法名相同并且参数个数相同if (!name.equals(m.getName())|| !sameType(args, m.getParameterTypes())) {return super.visitMethod(access, name, desc, signature,exceptions);}MethodVisitor v = cv.visitMethod(access, name, desc, signature,exceptions);return new MethodVisitor(Opcodes.ASM4, v) {@Overridepublic void visitLocalVariable(String name, String desc,String signature, Label start, Label end, int index) {int i = index - 1;// 如果是静态方法，则第一就是参数// 如果不是静态方法，则第一个是"this"，然后才是方法的参数if(Modifier.isStatic(m.getModifiers())) {i = index;}if (i >= 0 && i < paramNames.length) {paramNames[i] = name;}super.visitLocalVariable(name, desc, signature, start,end, index);}};}}, 0);return paramNames;}public static void main(String[] args) throws SecurityException,NoSuchMethodException {String[] s = getMethodParamNames(Dates.class.getMethod("parse",String.class,String.class));System.out.println(Strings.join(s));s = getMethodParamNames(Dates.class.getMethod("parse",String.class,String[].class));System.out.println(Strings.join(s));}}