Java Cron 到人类可读的字符串
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Cron to human readable string
提问by Savvas Dalkitsis
I am using Quartz with Java to schedule jobs. One thing is that i store cron expressions on a database and i would like to present them to a user but in a more readable form. So i was wondering if there is a utility that could convert a cron expression into a human readable string. Something like :
我正在使用 Quartz 和 Java 来安排作业。一件事是我将 cron 表达式存储在数据库中，我想以更易读的形式将它们呈现给用户。所以我想知道是否有一个实用程序可以将 cron 表达式转换为人类可读的字符串。就像是 ：
""0 30 10-13 ? * WED,FRI" will become "Fires at 10:30, 11:30, 12:30, and 13:30, on every Wednesday and Friday."
""0 30 10-13 ? * WED,FRI”将变为“每周三和周五的 10:30、11:30、12:30 和 13:30 触发”。
采纳答案by jazzhammer
A Java library that converts cron expressions into human readable strings: https://github.com/RedHogs/cron-parser
将 cron 表达式转换为人类可读字符串的 Java 库：https: //github.com/RedHogs/cron-parser
回答by Niels Peter Strandberg
The CronTrigger creates a CronExpression object from the cron expression String. But you cannot get access to it. But by using reflection you can:
CronTrigger 从 cron 表达式字符串创建一个 CronExpression 对象。但是您无法访问它。但是通过使用反射，您可以：
Class c = cronTrigger.getClass();
Field f = c.getDeclaredField("cronEx");
f.setAccessible(true);
CronExpression cronEx = (CronExpression) f.get(cronTrigger);
回答by Niels Peter Strandberg
Well yes I did understand your question. But I should have explained my answer a little better.
嗯，是的，我确实理解你的问题。但我应该更好地解释我的答案。
No I don't know any tool that will help you get a cron expression in “human” readable form. But by getting access to the CronExpression you can create you own.
不，我不知道有什么工具可以帮助您以“人类”可读的形式获得 cron 表达式。但是通过访问 CronExpression，您可以创建您自己的。
Try calling
试试打电话
cronTrigger.getExpressionSummary()
on the cron expression:
在 cron 表达式上：
"0/2 * * 4 * ?"
it returns the following String:
它返回以下字符串：
seconds: 0,2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40,42,44,46,48,50,52,54,56,58
minutes: *
hours: *
daysOfMonth: 4
months: *
daysOfWeek: ?
lastdayOfWeek: false
nearestWeekday: false
NthDayOfWeek: 0
lastdayOfMonth: false
calendardayOfWeek: false
calendardayOfMonth: false
years: *
By having access to the CronExpression object, you can create your own "human" explenation.
通过访问 CronExpression 对象，您可以创建自己的“人类”解释。
回答by jazzhammer
here's one i started. it uses the language that my users will ( probably ) understand.
这是我开始的一个。它使用我的用户（可能）理解的语言。
it won't do that well with mixtures of tokens like '1,13,16-23,L' for the dayofmonth token, but hopefully, i'll have some time to spend on it before my users become that sophisticated:
对于 dayofmonth 令牌，它不会像 '1,13,16-23,L' 这样的令牌混合使用，但希望在我的用户变得那么复杂之前，我有一些时间花在它上面：
package com.tacteonltd.control.cron;
import java.util.StringTokenizer;
import com.tacteonltd.control.string.STRING;
import com.tacteonltd.control.time.TIME;
public class CRON {
public static String humanReadable(String value){
StringBuffer sb = new StringBuffer();
try{
StringTokenizer tokens = new StringTokenizer(value, " ", false);
humanizeSeconds(tokens.nextToken(), sb);sb.append("\n");
humanizeMinutes(tokens.nextToken(), sb);sb.append("\n");
humanizeHours(tokens.nextToken(), sb);sb.append("\n");
String dom = tokens.nextToken();
String month = tokens.nextToken();
String dow = tokens.nextToken();
humanizeDOMs(dom, dow, sb);sb.append("\n");
humanizeMonths(month, sb);sb.append("\n");
humanizeDOWs(dow, dom, sb);
}catch(Throwable t){
t.printStackTrace();
}
return sb.toString();
}
private static void humanizeDOWs(String value, String dom, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("and the " + value + postFix(value) + " day-of-the-week("+TIME.getWeekDayName(Integer.parseInt(value))+"). ");
}
else if(value.equals("*"))
{
sb.append("and every day-of-the-week. ");
}
else if(value.equals("?"))
{
sb.append("and whatever day-of-the-week it is for day"+(STRING.isNumeric(dom) ? "":"s")+"-of-the-month :"+(STRING.isNumeric(dom) ? dom:"that match"+(STRING.isNumeric(dom) ? "es":"")+" " + dom + "."));
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("and the " + first + postFix(first) + " day-of-the-week and every " + every + " day" + (Integer.parseInt(every) == 1 ? "":"s") + " following. ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("and the following days of the week: ");
int added = 0;
while(tokens.hasMoreTokens()){
String token = tokens.nextToken();
sb.append((added==0 ? "":", ") + token);added++;
}
sb.append(".");
}
else if(value.indexOf("-")>-1){
StringTokenizer tokens = new StringTokenizer(value, "-", false);
sb.append("and for every day of the week from " + tokens.nextToken() + " through " + tokens.nextToken() + ". ");
}
else {
sb.append("and the following days of the week: " + value + ".");
}
}
private static void humanizeMonths(String value, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("the " + value + postFix(value) + " month("+TIME.getMonthName(Integer.parseInt(value))+"), ");
}
else if(value.equals("*"))
{
sb.append("every month, ");
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("the " + first + postFix(first) + " month("+TIME.getMonthName(Integer.parseInt(value))+") and every " + every + " month" + (Integer.parseInt(every) == 1 ? "":"s") + " following, ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("the following months: ");
int added = 0;
while(tokens.hasMoreTokens()){
sb.append((added==0 ? "":", ") + tokens.nextToken());added++;
}
}
}
private static void humanizeDOMs(String value, String dow, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("the " + value + postFix(value) + " day-of-the-month, ");
}
else if(value.equals("*"))
{
sb.append("every day-of-the-month, ");
}
else if(value.equals("?"))
{
sb.append("whatever day-of-the-month falls upon " + dow + " , ");
}
else if(value.indexOf("-")>-1){
StringTokenizer tokens = new StringTokenizer(value, "-", false);
String from = tokens.nextToken();
String through = tokens.nextToken();
int year = TIME.getYear(System.currentTimeMillis());
int month = TIME.getMonth(System.currentTimeMillis());
String last_dom = "" + TIME.getLastDOM(year, month);
sb.append("for every day of the month from " + from + " through " + (through.equals("L") ? "the last("+year +"." +month + "."+last_dom+")":through) );
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("the " + first + postFix(first) + " day-of-the-month and every " + every + " day" + (Integer.parseInt(every) == 1 ? "":"s") + " following, ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("the following days of the month: ");
int added = 0;
while(tokens.hasMoreTokens()){
String token = tokens.nextToken();
if(token.equals("L")){
int year = TIME.getYear(System.currentTimeMillis());
int month = TIME.getMonth(System.currentTimeMillis());
String last_dom = "" + TIME.getLastDOM(year, month);
sb.append((added==0 ? "":", ") + "the last("+year +"." +month + "."+last_dom+")");
}
else{
sb.append((added==0 ? "":", ") + token);added++;
}
}
}
}
private static void humanizeSeconds(String value, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("on the " + value + postFix(value) + " second, ");
}
else if(value.equals("*"))
{
sb.append("on every second, ");
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("on the " + first + postFix(first) + " second and every " + every + " second" + (Integer.parseInt(every) == 1 ? "":"s") + " following, ");
}
else if(value.indexOf("-")>-1){
StringTokenizer tokens = new StringTokenizer(value, "-", false);
sb.append("for every second from " + tokens.nextToken() + " through " + tokens.nextToken() + " ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("on the following seconds: ");
int added = 0;
while(tokens.hasMoreTokens()){
sb.append((added==0 ? "":", ") + tokens.nextToken());added++;
}
}
}
private static void humanizeMinutes(String value, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("the " + value + postFix(value) + " minute, ");
}
else if(value.equals("*"))
{
sb.append("every minute, ");
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("the " + first + postFix(first) + " minute and every " + every + " minute" + (Integer.parseInt(every) == 1 ? "":"s") + " following, ");
}
else if(value.indexOf("-")>-1){
StringTokenizer tokens = new StringTokenizer(value, "-", false);
sb.append("for every minute from " + tokens.nextToken() + " through " + tokens.nextToken() + " ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("the following minutes: ");
int added = 0;
while(tokens.hasMoreTokens()){
sb.append((added==0 ? "":", ") + tokens.nextToken());added++;
}
}
}
private static void humanizeHours(String value, StringBuffer sb){
value=value.trim();
if(STRING.isNumeric(value)){
sb.append("the " + value + postFix(value) + " hour, ");
}
else if(value.equals("*"))
{
sb.append("every hour, ");
}
else if(value.indexOf("/")>-1){
String first = value.substring(0, value.indexOf("/"));
String every = value.substring(value.indexOf("/") + 1);
sb.append("the " + first + postFix(first) + " hour and every " + every + " hour" + (Integer.parseInt(every) == 1 ? "":"s") + " following, ");
}
else if(value.indexOf("-")>-1){
StringTokenizer tokens = new StringTokenizer(value, "-", false);
sb.append("for every hour from " + tokens.nextToken() + " through " + tokens.nextToken() + " ");
}
else if(value.indexOf(",")>-1){
StringTokenizer tokens = new StringTokenizer(value, ",", false);
sb.append("the following hours: ");
int added = 0;
while(tokens.hasMoreTokens()){
sb.append((added==0 ? "":", ") + tokens.nextToken());added++;
}
}
}
private static String postFix(String value){
String post = null;
if(value.substring(value.length()-1).equals("1"))post = "st";
else if(value.substring(value.length()-1).equals("2"))post = "nd";
else if(value.substring(value.length()-1).equals("3"))post = "rd";
else post="th";
return post;
}
}
回答by kekec
cron-utilsmay be useful for this task, since provides human readable descriptions and does not require a fully fledged scheduler to provide them. Is well documented and supports multiple cron formats.
cron-utils可能对这项任务很有用，因为它提供了人类可读的描述，并且不需要完全成熟的调度程序来提供它们。有据可查并支持多种 cron 格式。
Below a code snippet from the docs:
在文档中的代码片段下方：
//create a descriptor for a specific Locale
CronDescriptor descriptor = CronDescriptor.instance(Locale.UK);
//parse some expression and ask descriptor for description
String description = descriptor.describe(parser.parse("*/45 * * * * *"));
//description will be: "every 45 seconds"
