Java自定义Cron，解析Cron表达式

Cron表达式中周和数字是不对应的
周一：2；周二：3；周三：4；周四：5；周五：6；周六：7；周日：1

pom文件必须依赖

		<dependency>
            <groupId>com.cronutils</groupId>
            <artifactId>cron-utils</artifactId>
            <version>9.1.1</version>
        </dependency>
        <dependency>
            <groupId>com.google.code.google-collections</groupId>
            <artifactId>google-collect</artifactId>
            <version>snapshot-20080530</version>
        </dependency>

创建CronUtils工具类

package com.example.demo.utils;

import com.cronutils.model.CronType;
import com.cronutils.model.definition.CronDefinition;
import com.cronutils.model.definition.CronDefinitionBuilder;
import com.cronutils.parser.CronParser;
import com.google.common.collect.Lists;
import lombok.Data;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * ClassName : CronUtils
 * Description : Cron表达式工具类
 * Author : x x x
 * Date : 2021/6/3 3:10 下午
 */
@Component
public class CronUtils {
   
   
    private static final Logger LOGGER = LoggerFactory.getLogger(CronUtils.class);

    private static final String QUESTION = "?";

    private static final String ASTERISK = "*";

    private static final String COMMA = ",";

    /**
     * 替换 分钟、小时、日期、星期
     */
    private static final String ORIGINAL_CRON = "0 %s %s %s * %s";

    /**
     * 检查cron表达式的合法性
     */
    public boolean checkValid(String cron) {
   
   
        try {
   
   
            CronDefinition cronDefinition = CronDefinitionBuilder.instanceDefinitionFor(CronType.SPRING);
            CronParser parser = new CronParser(cronDefinition);
            parser.parse(cron);
        } catch (IllegalArgumentException e) {
   
   
            LOGGER.error(String.format("cron=%s not valid", cron));
            return false;
        }
        return true;
    }

    public String buildCron(List<Integer> minutes, List<Integer> hours, List<Integer> weekdays) {
   
   
        String minute;
        if (minutes.equals(this.getInitMinutes())) {
   
   
            minute = ASTERISK;
        } else {
   
   
            minute = StringUtils.join(minutes, COMMA);
        }
        String hour;
        if (hours.equals(this.getInitHours())) {
   
   
            hour = ASTERISK;
        } else {
   
   
            hour = StringUtils.join(hours, COMMA);
        }
        String weekday;
        if (weekdays.equals(this.getInitWeekdays())) {
   
   
            weekday = QUESTION;
        } else {
   
   
            weekday = StringUtils.join(weekdays, COMMA);
        }
        // 重点：星期和日字段冲突，判断周日的前端输入
        if (weekday.equals(QUESTION)) {
   
   
            return String.format(ORIGINAL_CRON, minute, hour, ASTERISK, weekday);
        } else {
   
   
            return String.format(ORIGINAL_CRON, minute, hour, QUESTION, weekday);
        }
    }

    /**
     * 解析cron
     */
    public CustomCronField parseCon(String cron) {
   
   
        if (!this.checkValid(cron)) {
   
   
            return null;
        }
        List<String> result = Arrays.asList(cron.trim().split(" "));
        CustomCronField field = new CustomCronField()