tools/erlanalysis/src/main/java/org/apache/dubbo/erlang/analysis/utils/MethodParseUtil.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.dubbo.erlang.analysis.utils;

import org.objectweb.asm.*;


import java.io.IOException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

public class MethodParseUtil {
    public static String[] getMethodParamNames(final Method method) throws IOException {

        final String methodName = method.getName();
        final Class<?>[] methodParameterTypes = method.getParameterTypes();
        final int methodParameterCount = methodParameterTypes.length;
        final String className = method.getDeclaringClass().getName();
        final boolean isStatic = Modifier.isStatic(method.getModifiers());
        final String[] methodParametersNames = new String[methodParameterCount];

        ClassReader cr = new ClassReader(Thread.currentThread().getContextClassLoader().getResourceAsStream(className.replace('.', '/') + ".class"));
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_MAXS);
        cr.accept(new ClassVisitor(Opcodes.ASM5, cw) {
            public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {

                MethodVisitor mv = super.visitMethod(access, name, desc, signature, exceptions);

                final Type[] argTypes = Type.getArgumentTypes(desc);

                //参数类型不一致
                if (!methodName.equals(name) || !matchTypes(argTypes, methodParameterTypes)) {
                    return mv;
                }

                return new MethodVisitor(Opcodes.ASM5, mv) {
                    public void visitLocalVariable(String name, String desc, String signature, Label start, Label end, int index) {
                        //如果是静态方法，第一个参数就是方法参数，非静态方法，则第一个参数是 this ,然后才是方法的参数
                        int methodParameterIndex = isStatic ? index : index - 1;
                        if (0 <= methodParameterIndex && methodParameterIndex < methodParameterCount) {
                            methodParametersNames[methodParameterIndex] = name;
                        }
                        super.visitLocalVariable(name, desc, signature, start, end, index);
                    }
                };
            }
        }, 0);
        return methodParametersNames;
    }

    private static boolean matchTypes(Type[] types, Class<?>[] parameterTypes) {
        if (types.length != parameterTypes.length) {
            return false;
        }
        for (int i = 0; i < types.length; i++) {
            if (!Type.getType(parameterTypes[i]).equals(types[i])) {
                return false;
            }
        }
        return true;
    }
}