一个无用工具类

package com.ruben.utils;/**
 * @ClassName: FunctionUtils
 * @Date: 2020/11/9 0009 23:43
 * @Description:
 */

import com.baomidou.mybatisplus.core.toolkit.ExceptionUtils;
import com.baomidou.mybatisplus.core.toolkit.support.SerializedLambda;
import com.ruben.pojo.User;

import java.io.*;
import java.util.HashMap;
import java.util.Map;

/**
 * @ClassName: FunctionUtils
 * @Description: 我还没有写描述
 * @Date: 2020/11/9 0009 23:43
 * *
 * @author: <achao1441470436@gmail.com>
 * @version: 1.0
 * @since: JDK 1.8
 */
public class FunctionUtils {

    @FunctionalInterface
    public interface IFunction<T, R> extends Serializable {
        R apply(T t);
    }

    public static String getAttributeName(IFunction func) {
        if (!func.getClass().isSynthetic()) {
            throw ExceptionUtils.mpe("该方法仅能传入 lambda 表达式产生的合成类");
        }
        SerializedLambda lambda;
        try {
            ByteArrayOutputStream baos = new ByteArrayOutputStream(1024);
            ObjectOutputStream oos = new ObjectOutputStream(baos);
            oos.writeObject(func);
            oos.flush();
            ObjectInputStream objIn = new ObjectInputStream(new ByteArrayInputStream(baos.toByteArray())) {
                @Override
                protected Class<?> resolveClass(ObjectStreamClass objectStreamClass) throws IOException, ClassNotFoundException {
                    Class<?> clazz = super.resolveClass(objectStreamClass);
                    return clazz == java.lang.invoke.SerializedLambda.class ? SerializedLambda.class : clazz;
                }
            };
            lambda = (SerializedLambda) objIn.readObject();
        } catch (IOException | ClassNotFoundException e) {
            throw new RuntimeException("这不可能发生！", e);
        }
        String methodName = lambda.getImplMethodName();
        return methodName.substring(3, 4).toLowerCase() + methodName.substring(4);
    }


    public static void main(String[] args) {
        User user = new User();
        Map<String, Object> map = new HashMap<>(1 << 4);
        IFunction<User, String> getUsername = User::getUsername;
        map.put(FunctionUtils.getAttributeName(getUsername), user.getUsername());
    }


}